Power conversion device

Abstract

To provide a technique capable of restraining imbalance in current flowing through each semiconductor switch in a power conversion device in which a plurality of switch legs composed of semiconductor switches corresponding to upper and lower arms are connected in parallel.SOLUTION: A power conversion device 1 includes a smoothing circuit 20, an inverter circuit 40, and an output terminal 40T. The inverter circuit 40 includes a U-phase parallel connection bus bar 41O1 that connects AC output terminals 410O to each other. The U-phase parallel connection bus bar 41O1 passes through each of all arms included in a plurality of switch modules 410. The individual paths between the smoothing circuit 20 and a junction where all the paths from the plurality of switch modules 410 join are configured such that the lengths of the individual paths are approximately equal to each other and the current densities throughout the entire path for each individual path is approximately equal to each other.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present disclosure relates to a power conversion device. [Background technology]

[0002] 2. Description of the Related Art In a power conversion device in which a plurality of switch legs, each of which is made up of semiconductor switches corresponding to upper and lower arms, are connected in parallel, a technique for equalizing the current flowing through each semiconductor switch is known (see, for example, Patent Document 1).

[0003] In Patent Document 1, the switch legs are arranged in the width direction, and a parallel connection bus bar that connects in parallel the connection points between the upper and lower arms of each switch leg, and an output bus bar connected to the parallel connection bus bar are provided. The parallel connection bus bar occupies the width direction range in which each switch leg is arranged, and is provided to extend in the length direction from each switch leg. The output bus bar is laminated with the parallel connection bus bar via an insulating layer at the other end of the parallel connection bus bar opposite to each switch leg in the length direction, and is provided to extend in the width direction, and is connected to the parallel connection bus bar at one end in the width direction.

[0004] As a result, in Patent Document 1, the current flowing through the parallel connection busbar (i.e., the currents merging from each switch leg or branching to each switch leg) and the current flowing through the output busbar flow in opposite directions, and the magnetic fields generated by each current can be offset. This reduces the inductance of the power path in the width direction of the parallel connection busbar when the currents of each switch leg merge or branch, making it possible to suppress imbalance in the currents flowing through each switch leg. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-055478 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in Patent Document 1, the current in the output busbar corresponds to the sum of the currents in all the switch legs, whereas the current flowing in the width direction at the other end of the parallel connection busbar is merely the sum of the currents that have passed through one switch leg or some of the switch legs. Therefore, there is a possibility that the magnetic field generated by the output busbar will remain without being offset by the magnetic field generated by the parallel connection busbar. Therefore, when this magnetic field interlinks with the current flowing in the width direction of the parallel connection busbar, inductance is generated in the current path in the width direction of the parallel connection busbar, and there is a possibility that an imbalance will occur in the current flowing in each switch leg.

[0007] In view of the above problems, an object of the present invention is to provide a technology capable of suppressing imbalance in current flowing through each semiconductor switch in a power conversion device in which multiple switch legs, each of which is composed of semiconductor switches corresponding to upper and lower arms, are connected in parallel. [Means for solving the problem]

[0008] In order to achieve the above object, in one embodiment of the present disclosure, A smoothing circuit; an inverter circuit including a bridge circuit in which a plurality of switch legs, each having upper and lower arms each including a plurality of semiconductor switches connected in series, are connected in parallel, and output circuits, each having connection points of the upper and lower arms of the plurality of switch legs connected to each other, are connected in parallel for a plurality of phases, and the inverter circuit outputs a predetermined AC power based on the DC power input from the smoothing circuit; an output terminal that outputs the predetermined AC power to an outside, the inverter circuit includes: a positive-side DC bus bar connecting positive terminals of the plurality of switch legs together; a negative-side DC bus bar connecting negative terminals of the plurality of switch legs together; and a parallel-connection bus bar connecting connection points of the upper and lower arms of each of the plurality of switch legs together; the positive DC bus bar and the negative DC bus bar have a laminate structure in which they are laminated with an insulating layer interposed therebetween, the parallel connection bus bar is configured such that individual paths between the smoothing circuit and a junction where all paths from each of the plurality of switch legs join, the individual paths passing through each of all the arms included in the plurality of switch legs, have approximately equal lengths and have approximately equal current densities throughout the entire paths. A power converter is provided. Effect of the Invention

[0009] According to the above-described embodiment, it is possible to provide a technology capable of suppressing imbalance in current flowing through each semiconductor switch in a power conversion device in which multiple switch legs, each of which is composed of semiconductor switches corresponding to upper and lower arms, are connected in parallel. [Brief description of the drawings]

[0010] [Figure 1] 1 is a circuit diagram illustrating an example of a power conversion device according to a first embodiment. [Diagram 2] 1 is a structural diagram illustrating an example of a power conversion device according to a first embodiment. [Diagram 3] 1 is a structural diagram illustrating an example of a power conversion device according to a first embodiment. [Figure 4] FIG. 2 is a diagram illustrating an example of a bus bar arrangement structure. [Diagram 5] FIG. 2 is a diagram illustrating an example of a bus bar arrangement structure. [Figure 6] FIG. 2 is a diagram illustrating an example of a bus bar arrangement structure. [Figure 7] FIG. 2 is a circuit diagram showing an example of a power conversion device according to second to fourth embodiments. [Figure 8] FIG. 11 is a structural diagram illustrating an example of a power conversion device according to a second embodiment. [Figure 9] FIG. 11 is a structural diagram illustrating an example of a power conversion device according to a second embodiment. [Figure 10]4A and 4B are diagrams illustrating paths of current flowing through each switch module. [Figure 11] FIG. 11 is a structural diagram showing an example of a power conversion device according to a third embodiment. [Figure 12] FIG. 11 is a structural diagram showing an example of a power conversion device according to a third embodiment. [Figure 13] FIG. 13 is a structural diagram showing an example of a power conversion device according to a fourth embodiment. [Figure 14] FIG. 13 is a structural diagram showing an example of a power conversion device according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment will be described with reference to the drawings.

[0012] [First embodiment] First, the first embodiment will be described with reference to FIGS.

[0013] <Outline of power conversion device> FIG. 1 is a circuit diagram showing an example of a power conversion device 1 according to the first embodiment.

[0014] The power conversion device 1 generates a predetermined three-phase AC power using three-phase AC power input from a predetermined external power source (e.g., a commercial power system) and supplies the generated three-phase AC power to a predetermined load device (e.g., an electric motor).

[0015] As shown in FIG. 1, the power conversion device 1 includes a rectifier circuit 10, a smoothing circuit 20, a fuse 30, and an inverter circuit 40.

[0016] The rectifier circuit 10 rectifies three-phase AC power having R phase, S phase, and T phase, which is input from an external power source through an input terminal 11, and outputs a predetermined DC power to a smoothing circuit 20.

[0017] Input terminals 11 include an R-phase input terminal 111 to which R-phase power is input, an S-phase input terminal 112 to which S-phase power is input, and a T-phase input terminal 113 to which T-phase power is input.

[0018] As shown in FIG. 1, the rectifier circuit 10 is, for example, a bridge-type full-wave rectifier circuit in which six diodes 12 are connected in a bridge shape.

[0019] The smoothing circuit 20 smoothes the DC power output from the rectifier circuit 10 and the DC power regenerated from the inverter circuit 40 .

[0020] The smoothing circuit 20 includes a positive bus bar 20P, a negative bus bar 20N, and a smoothing capacitor 21.

[0021] The positive bus bar 20P is a flat plate-like member made of a material having a relatively high electrical conductivity (e.g., copper, aluminum, etc.) The same applies to the negative bus bar 20N, U-phase positive DC bus bar 41P, U-phase negative DC bus bar 41N, V-phase positive DC bus bar 42P, V-phase negative DC bus bar 42N, W-phase positive DC bus bar 43P, and W-phase negative DC bus bar 43N, which will be described below.

[0022] The positive bus bar 20P is connected to the positive output terminal of the rectifier circuit 10 and the positive input terminal of the inverter circuit 40.

[0023] The negative bus bar 20N is connected to the negative output terminal of the rectifier circuit 10 and the negative DC input terminal of the inverter circuit 40.

[0024] The smoothing capacitor 21 is disposed in a power path connecting the positive bus bar 20P and the negative bus bar 20N in parallel with the rectifier circuit 10 and the inverter circuit 40. The smoothing capacitor 21 smoothes the DC power output from the rectifier circuit 10 and the inverter circuit 40 while repeatedly charging and discharging as appropriate.

[0025] The smoothing capacitor 21 may be one, or a plurality of smoothing capacitors 21 may be connected in parallel (see FIGS. 2 and 3).

[0026] The smoothing capacitor 21 includes a positive terminal 21P connected to the positive bus bar 20P, and a negative terminal 21N connected to the negative bus bar 20N.

[0027] The fuse 30 is disposed on the positive power path between the positive bus bar 20P and the positive DC input terminal of the inverter circuit 40. The fuse 30 melts when an overcurrent or the like occurs, and protects the power conversion device 1 (inverter circuit 40) from damage or the like caused by an overcurrent associated with an overload, a short circuit, or the like.

[0028] The inverter circuit 40 generates three-phase AC power of U-phase, V-phase, and W-phase from the DC power supplied from the smoothing circuit 20, and outputs it to an external load device from the output terminal 40T. The output terminal 40T includes a U-phase output terminal 41T that outputs the U-phase AC power to the outside, a V-phase output terminal 42T that outputs the V-phase AC power to the outside, and a W-phase output terminal 43T that outputs the W-phase AC power to the outside.

[0029] The inverter circuit 40 includes a bridge circuit configured with a U-phase circuit 41, a V-phase circuit 42, and a W-phase circuit 43. The U-phase circuit 41, the V-phase circuit 42, and the W-phase circuit 43 (all of which are examples of output circuits) are connected in parallel between the positive wiring and the negative wiring of the power conversion device 1.

[0030] The U-phase circuit 41 includes a U-phase positive side DC bus bar 41P, a U-phase negative side DC bus bar 41N, switch modules 411-414, and a U-phase AC bus bar 410. Hereinafter, in the first embodiment, the switch modules 411-414 may be collectively referred to as "switch module 410," or any one of the switch modules 411-414 may be individually referred to as "switch module 410."

[0031] The U-phase positive DC bus bar 41P is connected to the positive bus bar 20P of the smoothing circuit 20 via a fuse 30.

[0032] The U-phase negative DC bus bar 41N is connected to the negative bus bar 20N of the smoothing circuit 20.

[0033] The switch modules 411 to 414 (an example of a switch leg) are connected in parallel between the U-phase positive side DC bus bar 41P and the U-phase negative side DC bus bar 41N.

[0034] The switch module 411 includes semiconductor switches 411s1 and 411s2 corresponding to upper and lower arms, free wheel diodes 411d1 and 411d2, a positive terminal 411P, a negative terminal 411N, and an AC output terminal 411O.

[0035] The switch module 412 includes semiconductor switches 412s1 and 412s2 corresponding to upper and lower arms, free wheel diodes 412d1 and 412d2, a positive terminal 412P, a negative terminal 412N, and an AC output terminal 412O.

[0036] The switch module 413 includes semiconductor switches 413s1 and 413s2 corresponding to upper and lower arms, free wheel diodes 413d1 and 413d2, a positive terminal 413P, a negative terminal 413N, and an AC output terminal 413O.

[0037] The switch module 414 includes semiconductor switches 414s1 and 414s2 corresponding to upper and lower arms, free wheel diodes 414d1 and 414d2, a positive terminal 414P, a negative terminal 414N, and an AC output terminal 414O.

[0038] Hereinafter, in the first embodiment, the semiconductor switches 411s1, 411s2, 412s1, 412s2, 413s1, 413s2, 414s1, and 414s2 may be collectively referred to as the "semiconductor switch 410s", or any one of them may be individually referred to as the "semiconductor switch 410s". In addition, in the first embodiment, the components corresponding to the positive terminals 411P to 414P of the above-mentioned "switch module 410" may be referred to as the "positive terminal 410P". In addition, in the first embodiment, the components corresponding to the negative terminals 411N to 414N of the above-mentioned "switch module 410" may be referred to as the "negative terminal 410N". In addition, in the first embodiment, the components corresponding to the AC output terminals 411O to 414O of the above-mentioned "switch module 410" may be referred to as the "AC output terminal 410O".

[0039] Since the switch modules 411 to 414 have similar components and are configured with similar circuits, the switch module 411 will be explained as a representative, and explanations of the switch modules 412 to 414 will be omitted.

[0040] The semiconductor switches 411s1 and 411s2 (examples of upper and lower arms) are disposed in a power path that connects the positive terminal 411P and the negative terminal 411N, and are connected in series to each other. The semiconductor switches 411s1 and 411s2 are, for example, IGBTs (Insulated Gate Bipolar Transistors).

[0041] The semiconductor switch 411s1 corresponds to the upper arm of the switch leg, and is connected to the positive terminal 411P.

[0042] The semiconductor switch 411s2 corresponds to the lower arm of the switch leg, and is connected to the negative terminal 411N.

[0043] The free wheel diodes 411d1 and 411d2 are connected in parallel to the semiconductor switches 411s1 and 411s2, respectively.

[0044] The positive terminal 411P is connected to a U-phase positive DC bus bar 41P.

[0045] The negative terminal 411N is connected to a U-phase negative DC bus bar 41N.

[0046] An AC output terminal 411O (an example of a connection point between the upper and lower arms) is drawn from a connection point (middle point) between the semiconductor switches 411s1 and 411s2.

[0047] One end of the U-phase AC bus bar 41O connects the AC output terminals 411O-414O of the switch modules 411-414 to each other, and the other end is connected to the U-phase output terminal 41T. This enables the inverter circuit 40 to output the U-phase AC power output from the switch modules 411-414 to the outside from the U-phase output terminal 41T.

[0048] The V-phase circuit 42 includes a V-phase positive side DC bus bar 42P, a V-phase negative side DC bus bar 42N, switch modules 421-424, and a V-phase AC bus bar 420. Hereinafter, in the first embodiment, the switch modules 421-424 may be collectively referred to as "switch module 420," or any one of the switch modules 421-424 may be individually referred to as "switch module 420."

[0049] The V-phase positive DC bus bar 42P is connected to the positive bus bar 20P of the smoothing circuit 20 via a fuse 30.

[0050] The V-phase negative DC bus bar 42N is connected to the negative bus bar 20N of the smoothing circuit 20.

[0051] The switch modules 421 to 424 are connected in parallel between the V-phase positive DC bus bar 42P and the V-phase negative DC bus bar 42N.

[0052] The switch module 421 includes semiconductor switches 421s1 and 421s2 corresponding to upper and lower arms, free wheel diodes 421d1 and 421d2, a positive terminal 421P, a negative terminal 421N, and an AC output terminal 421O.

[0053] The switch module 422 includes semiconductor switches 422s1 and 422s2 corresponding to upper and lower arms, free wheel diodes 422d1 and 422d2, a positive terminal 422P, a negative terminal 422N, and an AC output terminal 422O.

[0054] The switch module 423 includes semiconductor switches 423s1 and 423s2 corresponding to upper and lower arms, free wheel diodes 423d1 and 423d2, a positive terminal 423P, a negative terminal 423N, and an AC output terminal 423O.

[0055] The switch module 424 includes semiconductor switches 424s1 and 424s2 corresponding to upper and lower arms, free wheel diodes 424d1 and 424d2, a positive terminal 424P, a negative terminal 424N, and an AC output terminal 424O.

[0056] Hereinafter, in the first embodiment, the semiconductor switches 421s1, 421s2, 422s1, 422s2, 423s1, 423s2, 424s1, and 424s2 may be collectively referred to as the "semiconductor switch 420s", or any one of them may be individually referred to as the "semiconductor switch 420s". In addition, in the first embodiment, a component corresponding to the positive terminals 421P to 424P of the above-mentioned "switch module 420" may be referred to as the "positive terminal 420P". In addition, in the first embodiment, a component corresponding to the negative terminals 421N to 424N of the above-mentioned "switch module 420" may be referred to as the "negative terminal 420N". In addition, in the first embodiment, a component corresponding to the AC output terminals 421O to 424O of the above-mentioned "switch module 420" may be referred to as the "AC output terminal 420O".

[0057] Since the switch modules 421 to 424 have similar components and similar circuit configurations, the switch module 421 will be described as a representative, and descriptions of the switch modules 422 to 424 will be omitted.

[0058] The semiconductor switches 421s1 and 421s2 (examples of upper and lower arms) are disposed in a power path that connects the positive terminal 421P and the negative terminal 421N, and are connected in series with each other.

[0059] The semiconductor switch 421s1 corresponds to the upper arm of the switch leg, and is connected to the positive terminal 421P.

[0060] The semiconductor switch 421s2 corresponds to the lower arm of the switch leg, and is connected to the negative terminal 421N.

[0061] The free wheel diodes 421d1 and 421d2 are connected in parallel to the semiconductor switches 421s1 and 421s2, respectively.

[0062] The positive terminal 421P is connected to a V-phase positive DC bus bar 42P.

[0063] The negative terminal 421N is connected to a V-phase negative DC bus bar 42N.

[0064] An AC output terminal 421O (an example of a connection point between the upper and lower arms) is drawn from a connection point (middle point) between the semiconductor switches 421s1 and 421s2.

[0065] One end of V-phase AC bus bar 42O connects AC output terminals 421O-424O of switch modules 421-424 to each other, and the other end is connected to V-phase output terminal 42T. This enables inverter circuit 40 to output V-phase AC power output from switch modules 421-424 to the outside from V-phase output terminal 42T.

[0066] The W-phase circuit 43 includes a W-phase positive side DC bus bar 43P, a W-phase negative side DC bus bar 43N, switch modules 431-434, and a W-phase AC bus bar 430. Hereinafter, in the first embodiment, the switch modules 431-434 may be collectively referred to as "switch module 430," or any one of the switch modules 431-434 may be individually referred to as "switch module 430."

[0067] The W-phase positive DC bus bar 43P is connected to the positive bus bar 20P of the smoothing circuit 20 via a fuse 30.

[0068] The W-phase negative DC bus bar 43N is connected to the negative bus bar 20N of the smoothing circuit 20.

[0069] The switch modules 431 to 434 are connected in parallel between the W-phase positive DC bus bar 43P and the W-phase negative DC bus bar 43N.

[0070] The switch module 431 includes semiconductor switches 431s1 and 431s2 corresponding to upper and lower arms, free wheel diodes 431d1 and 431d2, a positive terminal 431P, a negative terminal 431N, and an AC output terminal 431O.

[0071] The switch module 432 includes semiconductor switches 432s1 and 432s2 corresponding to upper and lower arms, free wheel diodes 432d1 and 432d2, a positive terminal 432P, a negative terminal 432N, and an AC output terminal 432O.

[0072] The switch module 433 includes semiconductor switches 433s1 and 433s2 corresponding to upper and lower arms, free wheel diodes 433d1 and 433d2, a positive terminal 433P, a negative terminal 433N, and an AC output terminal 433O.

[0073] The switch module 434 includes semiconductor switches 434s1 and 434s2 corresponding to upper and lower arms, free wheel diodes 434d1 and 434d2, a positive terminal 434P, a negative terminal 434N, and an AC output terminal 434O.

[0074] Hereinafter, in the first embodiment, the semiconductor switches 431s1, 431s2, 432s1, 432s2, 433s1, 433s2, 434s1, and 434s2 may be collectively referred to as the "semiconductor switch 430s", or any one of them may be individually referred to as the "semiconductor switch 430s". In addition, in the first embodiment, the components corresponding to the positive terminals 431P to 434P of the above-mentioned "switch module 430" may be referred to as the "positive terminal 430P". In addition, in the first embodiment, the components corresponding to the negative terminals 431N to 434N of the above-mentioned "switch module 430" may be referred to as the "negative terminal 430N". In addition, in the first embodiment, the components corresponding to the AC output terminals 431O to 434O of the above-mentioned "switch module 430" may be referred to as the "AC output terminal 430O".

[0075] Since the switch modules 431 to 434 have similar components and similar circuit configurations, the switch module 431 will be described as a representative, and descriptions of the switch modules 432 to 434 will be omitted.

[0076] The semiconductor switches 431s1 and 431s2 (examples of upper and lower arms) are disposed in a power path that connects the positive terminal 431P and the negative terminal 431N, and are connected in series with each other.

[0077] The semiconductor switch 431s1 corresponds to the upper arm of the switch leg, and is connected to the positive terminal 431P.

[0078] The semiconductor switch 431s2 corresponds to the lower arm of the switch leg, and is connected to the negative terminal 431N.

[0079] The free wheel diodes 431d1 and 431d2 are connected in parallel to the semiconductor switches 431s1 and 431s2, respectively.

[0080] The positive terminal 431P is connected to a W-phase positive DC bus bar 43P.

[0081] The negative terminal 431N is connected to a W-phase negative DC bus bar 43N.

[0082] An AC output terminal 431O (an example of a connection point between the upper and lower arms) is drawn from a connection point (middle point) between the semiconductor switches 431s1 and 431s2.

[0083] One end of W-phase AC bus bar 43O connects AC output terminals 431O-434O of switch modules 431-434 to each other, and the other end is connected to W-phase output terminal 43T. This enables inverter circuit 40 to output W-phase AC power output from switch modules 431-434 to the outside from W-phase output terminal 43T.

[0084] <Structure of power conversion device> 2 and 3 are structural diagrams showing an example of the power converter 1 according to the first embodiment. Specifically, FIG. 2 is a perspective view showing a state in which a part of the housing 1H of the power converter 1 is removed, and FIG. 3 is an exploded perspective view showing a state in which a part of the housing 1H of the power converter 1 is removed and the output terminal 40T is removed and moved upward. FIGS. 4 to 6 are diagrams for explaining an example of the arrangement of the bus bars. Specifically, FIG. 4 is an exploded perspective view showing a schematic diagram of components of the bus bars disassembled, FIG. 5 is a perspective view showing a completed state in which the components of the bus bars in FIG. 4 are assembled, and FIG. 6 is a side view showing a schematic diagram of an example of the arrangement of the bus bars.

[0085] In Fig. 4 and Fig. 5, the laminated bus bar 20PN, the U-phase laminated bus bar 41PN, the V-phase laminated bus bar 42PN, and the W-phase laminated bus bar 43PN are drawn as an integrated member for convenience. In Fig. 4, the positive bus bar 20P of the smoothing circuit 20, and the U-phase positive DC bus bar 41P, the V-phase positive DC bus bar 42P, and the W-phase positive DC bus bar 43P of the inverter circuit 40 are drawn as an integrated member for convenience. Similarly, in Fig. 4, the negative bus bar 20N of the smoothing circuit 20, and the U-phase negative DC bus bar 41N, the V-phase negative DC bus bar 42N, and the W-phase negative DC bus bar 43N of the inverter circuit 40 are drawn as an integrated member for convenience. Similarly, in FIG. 4, the insulating layers 20I1, 41I1, 42I1, and 43I1 are drawn as an integral member. Similarly, in FIG. 4, the insulating layers 20I2, 41I2, 42I2, and 43I2 are drawn as an integral member. Also, in FIG. 4 and FIG. 5, for simplicity, only a portion (four pieces) of all the smoothing capacitors 21 of the smoothing circuit 20 are drawn as representatives. Similarly, in FIG. 4 and FIG. 5, for simplicity, only a portion (one piece) of all the switch modules 410 of the U-phase circuit 41 are drawn as representatives. Similarly, in FIG. 4 and FIG. 5, for simplicity, only a portion (one piece) of the switch modules 420 included in the V-phase circuit 42 are drawn as representatives. Similarly, in FIG. 4 and FIG. 5, for simplicity, only a portion (one piece) of the switch modules 430 included in the W-phase circuit 43 are drawn as representatives. Furthermore, in FIG. 6, for the sake of convenience, the insulating layers 20I1, 20I2, 41I1, 41I2, 42I1, 42I2, 43I1, and 43I2 are omitted from illustration.

[0086] 2 and 3, the power conversion device 1 has various components housed in a housing 1H that is generally rectangular and box-shaped when viewed from the top, side, and front. The word "generally" is intended to allow for manufacturing errors and the like, and will be used in the same sense hereinafter.

[0087] Hereinafter, the longitudinal direction of the housing 1H in top view may be referred to as the X-axis direction, the lateral direction of the housing 1H in top view may be referred to as the Y-axis direction, and the up-down direction may be referred to as the Z-axis direction (see FIGS. 2 to 6).

[0088] As shown in FIGS. 2 and 3, the smoothing circuit 20, the fuse 30, and the inverter circuit 40 are arranged in sequence from one end to the other end in the longitudinal direction inside the housing 1H (ie, in the positive direction of the X-axis).

[0089] The output terminal 40T is disposed in the center of the housing 1H in the longitudinal direction (X-axis direction) and in the upper part of the housing 1H. Specifically, the output terminal 40T is disposed above the smoothing circuit 20 and the fuse 30 inside the housing 1H.

[0090] As described above, the output terminal 40T includes the U-phase output terminal 41T, the V-phase output terminal 42T, and the W-phase output terminal 43T. The U-phase output terminal 41T, the V-phase output terminal 42T, and the W-phase output terminal 43T are arranged in sequence from one end portion in the short side direction inside the housing 1H to the center portion (i.e., in the positive direction of the Y axis).

[0091] In this example, the smoothing circuit 20 includes 24 smoothing capacitors 21 .

[0092] Smoothing capacitor 21 has a generally cylindrical shape and is placed on the bottom surface of housing 1H with its axial direction aligned in the vertical direction. A positive terminal 21P and a negative terminal 21N are provided on the end surface (upper end surface) opposite to the placement surface of smoothing capacitor 21.

[0093] Specifically, as shown in FIGS. 2 and 3, four smoothing capacitors 21 are arranged side by side in the X-axis direction, and six smoothing capacitors 21 are arranged side by side in the Y-axis direction.

[0094] On the upper end surface of the smoothing capacitor 21, a laminate bus bar 20PN is disposed substantially parallel to the X-axis direction and the Y-axis direction.

[0095] The laminated bus bar 20PN has a substantially rectangular shape when viewed from above. The laminated bus bar 20PN is disposed over an area covering the 24 smoothing capacitors 21 in the X-axis direction and the Y-axis direction.

[0096] 4 and 5, the laminated bus bar 20PN is configured by laminating the positive bus bar 20P and the negative bus bar 20N with an insulating layer 20I1 interposed therebetween. Specifically, the laminated bus bar 20PN has a four-layer laminate structure in which the negative bus bar 20N is disposed on the bottom layer, an insulating layer 20I1 is disposed thereon, the positive bus bar 20P is disposed thereon, and an insulating layer 20I2 is disposed on the top layer.

[0097] As shown in Figs. 4 to 6, the negative busbar 20N in the lowest layer is provided with a relatively small through hole to which the negative terminal 21N of the smoothing capacitor 21 is bolted. This allows direct connection between the negative terminal 21N of the smoothing capacitor 21 and the negative busbar 20N. Also, the negative busbar 20N is provided with a relatively large through hole to expose the positive terminal 21P in top view. This allows connection between the positive busbar 20P in a layer above the negative busbar 20N and the positive terminal 21P.

[0098] As shown in Figures 4 and 5, the insulating layer 20I1 adjacent to the upper surface of the negative bus bar 20N is provided with a relatively large through hole for exposing the positive terminal 21P and the negative terminal 21N of the smoothing capacitor 21 (i.e., the through hole for fastening the negative bus bar 20N) in a top view.

[0099] As shown in Figs. 4 to 6, the positive bus bar 20P adjacent to the insulating layer 20I1 has a relatively small through hole to which the positive terminal 21P of the smoothing capacitor 21 is fastened with a bolt. This allows the positive terminal 21P of the smoothing capacitor 21 and the positive bus bar 20P to be directly connected. Also, the positive bus bar 20P has a relatively large through hole to expose the negative terminal 21N of the smoothing capacitor 21 (i.e., the fastening through hole of the negative bus bar 20N) in a top view. This allows an operator to access the fastening through hole of the negative bus bar 20N which is in a layer below the positive bus bar 20P.

[0100] As shown in Figures 4 and 5, the uppermost insulating layer 20I2 is provided with a relatively large through hole that exposes the positive terminal 21P (i.e., the through hole for fastening the positive bus bar 20P) and the negative terminal 21N (i.e., the through hole for fastening the negative bus bar 20N) of the smoothing capacitor 21 in top view.

[0101] The positive bus bar 20P and the negative bus bar 20N of the laminated bus bar 20PN have, for example, substantially the same thickness, which makes the current densities of the positive bus bar 20P and the negative bus bar 20N substantially the same.

[0102] The laminated bus bar 20PN may be arranged in the housing 1H so that the overlapping area of ​​the positive bus bar 20P and the negative bus bar 20N is relatively large (preferably maximized). The thickness of the insulating layer 20I1 of the laminated bus bar 20PN may be set so that the distance between the positive bus bar 20P and the negative bus bar 20N is relatively small while ensuring the insulation between them. This allows the current paths flowing in opposite directions in space to be close to each other. Therefore, at least a part of the magnetic field generated by the current in the positive bus bar 20P and the magnetic field generated by the current in the negative bus bar 20N are offset, thereby reducing the inductance of the positive bus bar 20P and the negative bus bar 20N. Furthermore, as described above, when the current densities are approximately equal, the magnitudes of the magnetic fields generated by the currents in the positive bus bar 20P and the negative bus bar 20N are approximately equal, and most of the generated magnetic fields can be canceled out. This makes it possible to further reduce the inductance of the positive bus bar 20P and the negative bus bar 20N. As a result, the surge voltage of the power conversion device 1 can be suppressed as the inductance of the positive bus bar 20P and the negative bus bar 20N is reduced.

[0103] As described above, the inverter circuit 40 includes a bridge circuit configured with the U-phase circuit 41, the V-phase circuit 42, and the W-phase circuit 43.

[0104] As shown in Figures 2 and 3, the U-phase circuit 41, the V-phase circuit 42, and the W-phase circuit 43 are arranged in sequence in the Y-axis direction from the end in the negative direction of the Y-axis to the end in the positive direction of the Y-axis.

[0105] The U-phase circuit 41 includes four switch modules 410 (that is, equivalent to the above-mentioned switch modules 411 to 414).

[0106] The four switch modules 410 are arranged in two rows in the Y-axis direction, with two groups of two switch modules arranged in the X-axis direction. The four switch modules 410 are also arranged on other components (e.g., a control circuit of the power conversion device 1, drive circuits for the semiconductor switches 410s, 420s, and 430s, a cooling mechanism for the inverter circuit 40, etc.) placed on the bottom surface of the housing 1H. This makes it possible to relatively reduce the difference in the upper end position with the smoothing capacitor 21, which has a relatively large dimension in the Z-axis direction. Therefore, the positions of the positive bus bar 20P and the negative bus bar 20N in the Z-axis direction and the positions of the U-phase positive DC bus bar 41P and the U-phase negative DC bus bar 41N in the Z-axis direction can be relatively close to each other.

[0107] As shown in FIGS. 4 and 5, the switch module 410 has a box shape, and fastening notches and bolt bearing surfaces are provided at the corners in a top view.

[0108] The switch module 410 is arranged so that the longitudinal direction in a top view is approximately along the X-axis direction. In the switch module 410, an AC output terminal 410O, a negative terminal 410N, and a positive terminal 410P are arranged in order from the side closest to the smoothing circuit 20 (smoothing capacitor 21) along the longitudinal direction (i.e., the X-axis direction).

[0109] Note that a switch leg having a different configuration from the configuration in which a series-connected body of two semiconductor switches 410s is housed in a housing in advance, such as switch module 410, may be applied to U-phase circuit 41. The same may be applied to switch module 420 of V-phase circuit 42 and switch module 430 of W-phase circuit 43, and may be applied to second to fourth embodiments described below.

[0110] At the upper end of the switch module 410, a U-phase laminate bus bar 41PN is disposed approximately parallel to the X-axis direction and the Y-axis direction. Specifically, the U-phase laminate bus bar 41PN is configured to be integrally connected with a V-phase laminate bus bar 42PN and a W-phase laminate bus bar 43PN, which will be described later. That is, at the upper end of the switch module 410, a laminate bus bar 40PN including a U-phase laminate bus bar 41PN, a V-phase laminate bus bar 42PN, and a W-phase laminate bus bar 43PN is disposed approximately parallel to the X-axis direction and the Y-axis direction. The same applies to the second to fourth embodiments, which will be described later.

[0111] The U-phase laminate bus bar 41PN is disposed over a range covering the four switch modules 410 in the X-axis and Y-axis directions.

[0112] 4 and 5, the U-phase laminated bus bar 41PN is configured by laminating the U-phase positive side DC bus bar 41P and the U-phase negative side DC bus bar 41N with an insulating layer 41I1 interposed therebetween. Specifically, the U-phase laminated bus bar 41PN has a four-layer laminate structure in which the U-phase negative side DC bus bar 41N is arranged in the bottom layer, an insulating layer 41I1 is arranged thereon, the U-phase positive side DC bus bar 41P is arranged thereon, and an insulating layer 41I2 is arranged in the top layer.

[0113] The U-phase positive DC bus bar 41P is configured to be integrally connected to a V-phase positive DC bus bar 42P and a W-phase positive DC bus bar 43P (to be described later) (for example, as an integral plate-shaped member). That is, as shown in Fig. 6, the laminated bus bar 40PN includes a positive DC bus bar 40P configured to include a U-phase positive DC bus bar 41P, a V-phase positive DC bus bar 42P, and a W-phase positive DC bus bar 43P. The same applies to the second to fourth embodiments described below.

[0114] The U-phase negative DC bus bar 41N is configured to be integrally connected to a V-phase negative DC bus bar 42N and a W-phase negative DC bus bar 43N (for example, as an integral plate-shaped member), which will be described later. That is, as shown in Fig. 6, the laminated bus bar 40PN includes a negative DC bus bar 40N configured to include a U-phase negative DC bus bar 41N, a V-phase negative DC bus bar 42N, and a W-phase negative DC bus bar 43N. The same applies to the second to fourth embodiments described below.

[0115] The insulating layer 41I1 may be configured to be integrally connected to the insulating layers 42I1 and 43I1 described below (for example, as an integral plate-like member). Similarly, the insulating layer 42I2 may be configured to be integrally connected to the insulating layers 42I2 and 43I2 described below (for example, as an integral plate-like member). The same may be true for the second to fourth embodiments described below.

[0116] As shown in Figs. 4 to 6, the U-phase negative DC busbar 41N in the lowest layer is provided with a relatively small through hole to be bolted to the negative terminal 410N of the switch module 410. This allows direct connection between the negative terminal 410N of the switch module 410 and the U-phase negative DC busbar 41N. The U-phase negative DC busbar 41N is also provided with a relatively large, substantially rectangular through hole for exposing the positive terminal 410P in a top view. This allows connection between the U-phase positive DC busbar 41P in a layer above the U-phase negative DC busbar 41N and the positive terminal 410P. The U-phase negative DC busbar 41N is also provided with a relatively large, substantially rectangular through hole for exposing the AC output terminal 410O in a top view. This allows connection between the U-phase AC bus bar 41O located above the U-phase negative pole side DC bus bar 41N and the AC output terminal 410O.

[0117] 4 and 5, an insulating layer 41I1 adjacent to and above the U-phase negative DC bus bar 41N is provided with a relatively large, substantially rectangular through-hole corresponding to the switch module 410. This allows the positive terminal 410P, the negative terminal 410N (i.e., the through-hole for fastening the U-phase negative DC bus bar 41N), and the AC output terminal 410O to be exposed in top view.

[0118] As shown in Figs. 4 to 6, the U-phase positive DC bus bar 41P adjacent to the insulating layer 41I1 is provided with a relatively small through hole to be bolted to the positive terminal 410P of the switch module 410. This allows the positive terminal 410P of the switch module 410 to be directly connected to the U-phase positive DC bus bar 41P. Also, the U-phase positive DC bus bar 41P is provided with a relatively large through hole to expose the negative terminal 410N of the switch module 410 (i.e., the through hole for fastening the U-phase negative DC bus bar 41N) and the AC output terminal 410O in a top view. This allows an operator to access the through hole for fastening the U-phase negative DC bus bar 41N and the AC output terminal 410O, which are in a layer below the U-phase positive DC bus bar 41P.

[0119] 4 and 5, the uppermost insulating layer 41I2 is provided with a relatively large rectangular through hole corresponding to the switch module 410. This allows the positive terminal 410P (i.e., the through hole for fastening the U-phase positive DC bus bar 41P), the negative terminal 410N (i.e., the through hole for fastening the U-phase negative DC bus bar 41N), and the AC output terminal 410O of the switch module 410 to be exposed in top view.

[0120] The U-phase positive DC bus bar 41P and the U-phase negative DC bus bar 41N of the U-phase laminated bus bar 41PN have, for example, substantially the same thickness, so that the current densities of the U-phase positive DC bus bar 41P and the U-phase negative DC bus bar 41N are substantially equal.

[0121] 2 to 6, the U-phase AC bus bar 41O connects between the AC output terminal 410O and the U-phase output terminal 41T of the switch module 410. The U-phase AC bus bar 41O includes a U-phase parallel connection bus bar 41O1 and a U-phase output bus bar 41O2.

[0122] The U-phase parallel connection busbar 41O1 is a component part of the overall configuration of the U-phase AC busbar 41O for connecting in parallel the AC output terminals 410O of the four switch modules 410. Specifically, the U-phase parallel connection busbar 41O1 is a component part of the overall configuration of the U-phase AC busbar 41O for merging the power paths from the AC output terminals 410O of the four switch modules 410 to the U-phase output terminal 41T.

[0123] As shown in FIG. 2 and FIG. 3, the U-phase parallel connection bus bar 41O1 is configured to be plane symmetrical with respect to a plane perpendicular to the X-axis at a center position between two switch modules 410 arranged in the X-axis direction. The U-phase parallel connection bus bar 41O1 is also configured to be plane symmetrical with respect to a plane perpendicular to the Y-axis at a center position between two rows of switch modules 410 arranged in the Y-axis direction. The U-phase parallel connection bus bar 41O1 is connected to the U-phase output bus bar 41O2 at a portion corresponding to the center positions of the AC output terminals 410O of the four switch modules 410 in the X-axis direction and the Y-axis direction. This allows the lengths of the paths from the AC output terminals 410O of the four switch modules 410 to the U-phase output terminal 41T to be approximately equal. Also, the current density of each path from the AC output terminals 410O of the four switch modules 410 to the U-phase output terminal 41T can be approximately equal. Therefore, the inductances of the power paths between the four switch modules 410 and the U-phase output terminal 41T can be made substantially equal.

[0124] Specifically, the U-phase parallel-connection bus bar 41O1 includes two leg portions 41O1a and a connecting portion 41O1b.

[0125] The two legs 41O1a each have a flat plate shape that is approximately parallel to the X-axis direction and the Z-axis direction. The two legs 41O1a each connect the AC output terminals 410O of two switch modules 410 arranged in two rows in the Y-axis direction and aligned in the X-axis direction. The two legs 41O1a are configured to be plane-symmetrical with respect to a vertical plane with respect to the X-axis direction at approximately the center position between the AC output terminals 410O of the two switch modules 410 aligned in the X-axis direction. Specifically, the leg 41O1a includes two seating surfaces, two lower legs, a middle leg, and an upper leg. The two seating surfaces have an approximately rectangular shape in a top view, are placed on the AC output terminals 410O of the two switch modules 410 aligned in the X-axis direction, and have fastening holes for bolting to the AC output terminals 410O. The two lower legs are provided to extend upward from each of the two seating surfaces. The middle leg connects the two lower legs to each other so as to extend in the X-axis direction. The upper leg is provided so as to extend upward from the upper end of the middle leg and the center in the X-axis direction. As a result, the leg 41O1a can merge the paths from the AC output terminals 410O of the two switch modules 410 at approximately the same distance. Furthermore, the leg 41O1a can make the cross-sectional areas of the paths from the AC output terminals 410O of the two switch modules 410 approximately the same, and can make the current densities approximately the same. Furthermore, the two legs 41O1a are configured to be plane-symmetrical with respect to a vertical plane in the Y-axis direction at approximately the center position between the AC output terminals 410O of the two switch modules 410 arranged in the Y-axis direction. As a result, the two legs 41O1a can make the paths from the two switch modules 410 to the merge approximately the same distance.

[0126] The connecting portion 41O1b has a flat plate shape substantially parallel to the X-axis direction and the Y-axis direction, and connects two legs 41O1a arranged to be aligned in the Y-axis direction. Specifically, the connecting portion 41O1b has a substantially rectangular shape in a top view, and connects the upper legs of the two legs 41O1a to each other so as to extend in the Y-axis direction. The connecting portion 41O1b is configured to be plane-symmetrical with respect to a plane perpendicular to the Y-axis at a substantially central position between the two legs 41O1a in the Y-axis direction, that is, at a substantially central position between the AC output terminals 410O of the two (two rows) switch modules 410 aligned in the Y-axis direction. The connecting portion 41O1b is connected to the U-phase output bus bar 41O2 at a substantially central position between the two legs 41O1a in the Y-axis direction. As a result, the U-phase parallel-connection bus bar 41O1 merges paths from the four switch modules 410 in pairs of equal length, making all the paths approximately equal in length and allowing the current density of each path to be the same.

[0127] The U-phase output bus bar 41O2 is provided to extend in the negative direction of the X-axis in top view from the center in the Y-axis direction of the connecting portion 41O1b of the U-phase parallel connection bus bar 41O1, and is connected to the U-phase output terminal 41T.

[0128] The V-phase circuit 42 , like the U-phase circuit 41 , includes four switch modules 420 .

[0129] The arrangement of the four switch modules 420 is similar to that of the four switch modules 410 of the U-phase circuit 41, and therefore will not be described.

[0130] As shown in FIGS. 4 and 5, the external shape of the switch module 420 is similar to that of the switch module 410.

[0131] The switch module 420 is arranged such that the longitudinal direction in a top view is substantially along the X-axis direction. In the switch module 420, an AC output terminal 420O, a negative terminal 420N, and a positive terminal 420P are arranged in order from the side closest to the smoothing circuit 20 (smoothing capacitor 21) along the longitudinal direction (i.e., the X-axis direction).

[0132] At the upper end of the switch module 420, a V-phase laminate bus bar 42PN is disposed substantially parallel to the X-axis direction and the Y-axis direction.

[0133] The V-phase laminate bus bar 42PN is disposed over a range covering the four switch modules 420 in the X-axis and Y-axis directions.

[0134] 4 and 5, the V-phase laminated bus bar 42PN is configured by laminating the V-phase positive side DC bus bar 42P and the V-phase negative side DC bus bar 42N with an insulating layer 42I1 interposed therebetween. Specifically, the V-phase laminated bus bar 42PN has a four-layer laminate structure in which the V-phase negative side DC bus bar 42N is arranged in the bottom layer, an insulating layer 42I1 is arranged thereon, the V-phase positive side DC bus bar 42P is arranged thereon, and an insulating layer 42I2 is arranged in the top layer.

[0135] As described above, the V-phase positive DC bus bar 42P is integrally connected to the U-phase positive DC bus bar 41P and a W-phase positive DC bus bar 43P described below.

[0136] As described above, the V-phase negative DC bus bar 42N is integrally connected to the U-phase negative DC bus bar 41N and a W-phase negative DC bus bar 43N described below.

[0137] As described above, the insulating layer 42I1 may be configured to be integrally connected to the insulating layer 41I1 and the insulating layer 43I1 described below. Similarly, as described above, the insulating layer 42I2 may be configured to be integrally connected to the insulating layer 41I2 and the insulating layer 43I2 described below.

[0138] The detailed structure of the V-phase laminated bus bar 42PN is similar to that of the U-phase laminated bus bar 41PN, and therefore will not be described.

[0139] 2 to 6, the V-phase AC bus bar 42O connects between the AC output terminal 420O and the V-phase output terminal 42T of the switch module 420. The V-phase AC bus bar 42O includes a V-phase parallel connection bus bar 42O1 and a V-phase output bus bar 42O2.

[0140] The arrangement and structure of the V-phase AC bus bar 42O are similar to those of the U-phase AC bus bar 41O, and therefore will not be described.

[0141] The W-phase circuit 43 , like the U-phase circuit 41 , includes four switch modules 430 .

[0142] The arrangement of the four switch modules 430 is similar to that of the four switch modules 410 of the U-phase circuit 41, and therefore will not be described.

[0143] As shown in FIGS. 4 and 5, the external shape of the switch module 430 is similar to that of the switch module 410.

[0144] The switch module 430 is disposed so that the longitudinal direction in a top view is substantially along the X-axis direction. In the switch module 430, an AC output terminal 430O, a negative terminal 430N, and a positive terminal 430P are arranged in sequence from the side closest to the smoothing circuit 20 (smoothing capacitor 21) along the longitudinal direction (i.e., the X-axis direction).

[0145] At the upper end of the switch module 430, a W-phase laminate bus bar 43PN is disposed substantially parallel to the X-axis direction and the Y-axis direction.

[0146] The W-phase laminated bus bar 43PN is disposed over a range covering the four switch modules 430 in the X-axis and Y-axis directions.

[0147] 4 and 5, the W-phase laminated bus bar 43PN is configured by laminating the W-phase positive side DC bus bar 43P and the W-phase negative side DC bus bar 43N with an insulating layer 43I1 interposed therebetween. Specifically, the W-phase laminated bus bar 43PN has a four-layer laminate structure in which the W-phase negative side DC bus bar 43N is arranged in the bottom layer, an insulating layer 43I1 is arranged thereon, the W-phase positive side DC bus bar 43P is arranged thereon, and an insulating layer 43I2 is arranged in the top layer.

[0148] As described above, the W-phase positive DC bus bar 43P is configured to be integrally connected to the U-phase positive DC bus bar 41P and the V-phase positive DC bus bar 42P.

[0149] As described above, the W-phase negative DC bus bar 43N is configured to be integrally connected to the U-phase negative DC bus bar 41N and the V-phase negative DC bus bar 42N.

[0150] As described above, the insulating layer 43I1 may be configured to be integrally connected to the insulating layer 41I1 and the insulating layer 42I1. Similarly, the insulating layer 43I2 may be configured to be integrally connected to the insulating layer 41I2 and the insulating layer 42I2.

[0151] The detailed structure of the W-phase laminated bus bar 43PN is similar to that of the U-phase laminated bus bar 41PN, and therefore will not be described.

[0152] 2 to 6, the W-phase AC bus bar 43O connects between the AC output terminal 430O and the W-phase output terminal 43T of the switch module 430. The W-phase AC bus bar 43O includes a W-phase parallel connection bus bar 43O1 and a W-phase output bus bar 43O2.

[0153] The arrangement and structure of the W-phase AC bus bar 43O are similar to those of the U-phase AC bus bar 41O, and therefore a description thereof will be omitted.

[0154] The laminated bus bar 40PN may be arranged in the housing 1H so that the overlapping area of ​​the positive side DC bus bar 40P and the negative side DC bus bar 40N is relatively large (preferably maximized). The thickness of the insulating layers 41I1, 42I1, 43I1 of the laminated bus bar 40PN may be set so that the distance between the positive side DC bus bar 40P and the negative side DC bus bar 40N is relatively small while ensuring the insulation of the positive side DC bus bar 40P and the negative side DC bus bar 40N. This allows the current paths flowing in opposite directions in space to be close to each other. Therefore, at least a part of the magnetic field generated by the current of the positive side DC bus bar 40P and the magnetic field generated by the current of the negative side DC bus bar 40N can be offset. For example, when a U-phase current flows through the positive side DC bus bar 40P, a V-phase or W-phase current flows through the negative side DC bus bar 40N. Therefore, the inductance of the positive side DC busbar 40P and the negative side DC busbar 40N can be reduced. Furthermore, as described above, when the current densities are approximately equal, the magnitudes of the magnetic fields generated by the current of the positive side DC busbar 40P and the current of the negative side DC busbar 40N become approximately equal, and most of the generated magnetic fields can be canceled out. Therefore, the inductance of the positive side DC busbar 40P and the negative side DC busbar 40N can be further suppressed. Therefore, the surge voltage of the power conversion device 1 can be suppressed with the reduction in inductance of the positive side DC busbar 40P and the negative side DC busbar 40N.

[0155] In this manner, in the first embodiment, the positive bus bar 20P and the negative bus bar 20N of the smoothing circuit 20 have a laminate structure in which they are stacked with the insulating layer 20I1 interposed therebetween. Similarly, the positive DC bus bar 40P and the negative DC bus bar 40N of the inverter circuit 40 have a laminate structure in which they are stacked with the insulating layers 41I1, 42I1, and 43I1 interposed therebetween. This reduces and greatly reduces the inductance of the DC portion of the loop power path between the smoothing circuit 20 and the output terminal 40T. This makes it possible to suppress the surge voltage that accompanies the ON / OFF of the semiconductor switches 410s, 420s, and 430s of the power conversion device 1.

[0156] In the first embodiment, the U-phase parallel connection bus bar 41O1 is configured so that the lengths of the power paths from the AC output terminals 410O of the four switch modules 410 to the junction toward the U-phase output terminal 41T are approximately equal. Specifically, the U-phase parallel connection bus bar 41O1 is configured so that the lengths of the power paths between the AC output terminals 410O of the four switch modules 410 and the connection portion with the U-phase output bus bar 41O2 are approximately equal. This makes it possible to relatively reduce the difference in inductance of each of the power paths between the AC output terminals 410O of the four switch modules 410 and the U-phase output terminal 41T. Therefore, it is possible to relatively reduce the difference in inductance of each of the loop power paths through which the four switch modules 410 pass between the smoothing circuit 20 and the U-phase output terminal 41T. Moreover, the U-phase parallel connection bus bar 41O1 is configured so that the current density of each power path from the AC output terminal 410O of each of the four switch modules 410 to the junction toward the U-phase output terminal 41T is approximately equal. This allows the inductance of each power path between the AC output terminal 410O of each of the four switch modules 410 and the U-phase output terminal 41T to be approximately equal. Therefore, the inductance of each power path passing through the four switch modules 410 between the smoothing circuit 20 and the U-phase output terminal 41T can be approximately equal. Similarly, the V-phase parallel connection bus bar 42O1 is configured so that the length of each power path from the AC output terminal 420O of each of the four switch modules 420 to the junction toward the V-phase output terminal 42T is approximately equal. This allows the difference in inductance of each power path between the AC output terminal 420O of each of the four switch modules 420 and the V-phase output terminal 42T to be relatively small. This makes it possible to relatively reduce the difference in inductance between the smoothing circuit 20 and the V-phase output terminal 42T of each of the four switch modules 420. Furthermore, the V-phase parallel-connection bus bar 42O1 is configured so that the current densities of the power paths from the AC output terminals 420O of the four switch modules 420 to the joining point toward the V-phase output terminal 42T are approximately equal.This allows the inductances of the power paths between the AC output terminals 420O of the four switch modules 420 and the V-phase output terminal 42T to be all approximately equal. Therefore, the inductances of the power paths in a loop through the four switch modules 420 between the smoothing circuit 20 and the V-phase output terminal 42T can be approximately equal. Similarly, the W-phase parallel connection bus bar 43O1 is configured so that the lengths of the power paths from the AC output terminals 430O of the four switch modules 430 to the junction toward the W-phase output terminal 43T are approximately equal. This allows the difference in inductance of the power paths between the AC output terminals 430O of the four switch modules 430 and the W-phase output terminal 43T to be relatively small. Therefore, the difference in inductance of the power paths in a loop through the four switch modules 430 between the smoothing circuit 20 and the W-phase output terminal 43T can be relatively small. Moreover, the W-phase parallel connection bus bar 43O1 is configured so that the current density of each power path from the AC output terminal 430O of each of the four switch modules 430 to the junction toward the W-phase output terminal 43T is approximately equal. This allows the inductance of each power path between the AC output terminal 430O of each of the four switch modules 430 and the W-phase output terminal 43T to be approximately equal. Therefore, the inductance of each loop of power paths passing through the four switch modules 430 between the smoothing circuit 20 and the W-phase output terminal 43T can be approximately equal. As described above, this is because the inductance of the DC part of the loop of power paths between the smoothing circuit 20 and the output terminal 40T is very small and the inductance of the AC part is dominant. Therefore, it is possible to suppress the imbalance of the currents of the four switch modules 410, the four switch modules 420, and the four switch modules 430, and to equalize the currents.

[0157] In the first embodiment, the number of switch modules 410 connected in parallel may be any number as long as the lengths of the power paths from the AC output terminals 410O of the respective switch modules 410 to the U-phase output terminals 41T are substantially equal to each other. That is, the number of switch modules 410 connected in parallel may be two, three, or five or more. For example, when the number of switch modules 410 connected in parallel is two, the U-phase parallel connection bus bar 41O1 may be configured to include only the leg 41O1a and to be connected to the U-phase output bus bar 41O2 at a substantially central position (midpoint) in the X-axis direction of the upper end of the leg 41O1a. The number of switch modules 420 and switch modules 430 may be the same. In the first embodiment, the switch modules 410 may be arranged arbitrarily as long as the lengths of the power paths from the AC output terminals 410O of the switch modules 410 to the U-phase output terminals 41T of the switch modules 410 are substantially equal. For example, the switch modules 410 may be arranged in three or more rows in the X-axis direction. For example, the switch modules 410 may be arranged in a line in the X-axis direction, or in three or more rows in the Y-axis direction. For example, the number of modules arranged in each of the X-axis direction and the Y-axis direction is preferably a power of two. As a result, as described above, the lengths of all the paths and the current density of each path can be substantially equal while the paths from the AC output terminals 410O of the switch modules 410 are joined in pairs with equal lengths. The switch modules 420 and the switch modules 430 may be arranged in the same manner. Furthermore, in the first embodiment, the U-phase parallel-connection bus bar 41O1 may have any configuration as long as the lengths of the power paths from the AC output terminals 410O of the respective switch modules 410 to the U-phase output terminal 41T are approximately equal to each other. For example, the U-phase parallel-connection bus bar 41O1 does not need to have a plane-symmetric configuration as described above as long as the lengths of the power paths from the AC output terminals 410O of the four switch modules 410 to the U-phase output terminal 41T are approximately equal to each other.Specifically, the two legs 41O1a of the U-phase parallel connection bus bar 41O1 may have substantially the same shape spaced apart from each other in the Y-axis direction, rather than being symmetrical with respect to a plane perpendicular to the Y-axis direction. The V-phase parallel connection bus bar 42O1 and the W-phase parallel connection bus bar 43O1 may have the same configuration.

[0158] [Second embodiment] Next, a second embodiment will be described with reference to Fig. 7 to Fig. 10. Below, the description will be centered on the parts that are different from the power conversion device 1 according to the first embodiment, and the description of the same or corresponding contents as those in the first embodiment may be simplified or omitted.

[0159] <Outline of power conversion device> FIG. 7 is a circuit diagram showing an example of the power conversion device 1 according to the second embodiment.

[0160] As shown in FIG. 7, the power conversion device 1 includes a rectifier circuit 10, a smoothing circuit 20, a fuse 30, and an inverter circuit 40, similarly to the first embodiment.

[0161] The inverter circuit 40 includes a bridge circuit configured with a U-phase circuit 41, a V-phase circuit 42, and a W-phase circuit 43, similarly to the first embodiment.

[0162] As in the first embodiment, the U-phase circuit 41 includes a U-phase positive side DC bus bar 41P, a U-phase negative side DC bus bar 41N, switch modules 411-414, and a U-phase AC bus bar 41O. Unlike the first embodiment, the U-phase circuit 41 further includes switch modules 415 and 416. Hereinafter, in the second embodiment and in the third and fourth embodiments described later, the switch modules 411-416 may be collectively referred to as "switch module 410," or any one of the switch modules 411-416 may be individually referred to as "switch module 410." In other words, unlike the first embodiment, the U-phase circuit 41 includes six switch modules 410.

[0163] The switch modules 411 to 416 (an example of a switch leg) are connected in parallel between the U-phase positive side DC bus bar 41P and the U-phase negative side DC bus bar 41N.

[0164] The switch module 415 includes semiconductor switches 415s1 and 415s2 corresponding to upper and lower arms, free wheel diodes 415d1 and 415d2, a positive terminal 415P, a negative terminal 415N, and an AC output terminal 415O.

[0165] The switch module 416 includes semiconductor switches 416s1 and 416s2 corresponding to upper and lower arms, free wheel diodes 416d1 and 416d2, a positive terminal 416P, a negative terminal 416N, and an AC output terminal 416O.

[0166] Hereinafter, in the second embodiment and the third and fourth embodiments described later, the semiconductor switches 411s1, 411s2, 412s1, 412s2, 413s1, 413s2, 414s1, 414s2, 415s1, 415s2, 416s1, and 416s2 may be collectively referred to as the "semiconductor switch 410s", or any one of them may be individually referred to as the "semiconductor switch 410s". In addition, in the second embodiment and the third and fourth embodiments described later, components corresponding to the positive terminals 411P to 416P of the above-mentioned "switch module 410" may be referred to as the "positive terminal 410P". In addition, in the second embodiment and the third and fourth embodiments described later, components corresponding to the negative terminals 411N to 416N of the above-mentioned "switch module 410" may be referred to as the "negative terminal 410N". In the second embodiment, as well as the third and fourth embodiments described below, components corresponding to the AC output terminals 411O-416O of the above-mentioned "switch module 410" may be referred to as "AC output terminal 410O."

[0167] The switch modules 411 to 416 have similar components and are configured with similar circuits.

[0168] One end of the U-phase AC bus bar 41O connects the AC output terminals 411O-416O of the switch modules 411-416 to each other, and the other end is connected to the U-phase output terminal 41T. This enables the inverter circuit 40 to output the U-phase AC power output from the switch modules 411-416 to the outside from the U-phase output terminal 41T.

[0169] Similar to the first embodiment, the V-phase circuit 42 includes a V-phase positive side DC bus bar 42P, a V-phase negative side DC bus bar 42N, switch modules 421-424, and a V-phase AC bus bar 42O. Unlike the first embodiment, the V-phase circuit 42 further includes switch modules 425 and 426. Hereinafter, in the second embodiment and in the third and fourth embodiments described later, the switch modules 421-426 may be collectively referred to as "switch module 420," or any one of the switch modules 421-426 may be individually referred to as "switch module 420." In other words, unlike the first embodiment, the V-phase circuit 42 includes six switch modules 420.

[0170] The switch modules 421 to 426 are connected in parallel between the V-phase positive side DC bus bar 42P and the V-phase negative side DC bus bar 42N.

[0171] The switch module 425 includes semiconductor switches 425s1 and 425s2 corresponding to upper and lower arms, free wheel diodes 425d1 and 425d2, a positive terminal 425P, a negative terminal 425N, and an AC output terminal 425O.

[0172] The switch module 426 includes semiconductor switches 426s1 and 426s2 corresponding to upper and lower arms, free wheel diodes 426d1 and 426d2, a positive terminal 426P, a negative terminal 426N, and an AC output terminal 426O.

[0173] Hereinafter, in the second embodiment and the third and fourth embodiments described later, the semiconductor switches 421s1, 421s2, 422s1, 422s2, 423s1, 423s2, 424s1, 424s2, 425s1, 425s2, 426s1, and 426s2 may be collectively referred to as the "semiconductor switch 420s", or any one of them may be individually referred to as the "semiconductor switch 420s". In addition, in the second embodiment and the third and fourth embodiments described later, components corresponding to the positive terminals 421P to 426P of the above-mentioned "switch module 420" may be referred to as the "positive terminal 420P". In addition, in the second embodiment and the third and fourth embodiments described later, components corresponding to the negative terminals 421N to 426N of the above-mentioned "switch module 420" may be referred to as the "negative terminal 420N". In the second embodiment, and in the third and fourth embodiments described below, components corresponding to the AC output terminals 421O-426O of the above-mentioned "switch module 420" may be referred to as "AC output terminal 420O".

[0174] The switch modules 421 to 426 have similar components and are configured with similar circuits.

[0175] One end of V-phase AC bus bar 42O connects AC output terminals 421O-426O of switch modules 421-426 to each other, and the other end is connected to V-phase output terminal 42T. This enables inverter circuit 40 to output V-phase AC power output from switch modules 421-426 to the outside from V-phase output terminal 42T.

[0176] Similarly to the first embodiment, the W-phase circuit 43 includes a W-phase positive side DC bus bar 43P, a W-phase negative side DC bus bar 43N, switch modules 431-434, and a W-phase AC bus bar 43O. Unlike the first embodiment, the W-phase circuit 43 further includes switch modules 435 and 436. Hereinafter, in the second embodiment and in the third and fourth embodiments described later, the switch modules 431-436 may be collectively referred to as "switch module 430," or any one of the switch modules 431-436 may be individually referred to as "switch module 430." In other words, unlike the first embodiment, the W-phase circuit 43 includes six switch modules 430.

[0177] The switch modules 431 to 436 are connected in parallel between the W-phase positive DC bus bar 43P and the W-phase negative DC bus bar 43N.

[0178] The switch module 435 includes semiconductor switches 435s1 and 435s2 corresponding to upper and lower arms, free wheel diodes 435d1 and 435d2, a positive terminal 435P, a negative terminal 435N, and an AC output terminal 435O.

[0179] The switch module 436 includes semiconductor switches 436s1 and 436s2 corresponding to upper and lower arms, free wheel diodes 436d1 and 436d2, a positive terminal 436P, a negative terminal 436N, and an AC output terminal 436O.

[0180] Hereinafter, in the second embodiment and the third and fourth embodiments described later, the semiconductor switches 431s1, 431s2, 432s1, 432s2, 433s1, 433s2, 434s1, 434s2, 435s1, 435s2, 436s1, and 436s2 may be collectively referred to as the "semiconductor switch 430s", or any one of them may be individually referred to as the "semiconductor switch 430s". In addition, in the second embodiment and the third and fourth embodiments described later, the components corresponding to the positive terminals 431P to 436P of the above-mentioned "switch module 430" may be referred to as the "positive terminal 430P". In addition, in the second embodiment and the third and fourth embodiments described later, the components corresponding to the negative terminals 431N to 436N of the above-mentioned "switch module 430" may be referred to as the "negative terminal 430N". In the second embodiment, as well as the third and fourth embodiments described below, components corresponding to the AC output terminals 431O-436O of the above-mentioned "switch module 430" may be referred to as "AC output terminal 430O."

[0181] The switch modules 431 to 436 have similar components and are configured with similar circuits.

[0182] One end of W-phase AC bus bar 43O connects AC output terminals 431O-436O of switch modules 431-436 to each other, and the other end is connected to W-phase output terminal 43T. This enables inverter circuit 40 to output W-phase AC power output from switch modules 431-436 to the outside from W-phase output terminal 43T.

[0183] <Structure of power conversion device> 8 and 9 are structural diagrams showing an example of the power conversion device according to the second embodiment. Specifically, FIG. 8 is a perspective view showing a state in which a part of the housing 1H of the power conversion device 1 is removed. FIG. 9 is an exploded perspective view showing a state in which a part of the housing 1H of the power conversion device 1 is removed, and the output terminal 40T and the U-phase AC bus bar 41O, the V-phase AC bus bar 42O, and the W-phase AC bus bar 43O are removed and moved upward. FIG. 10 is a diagram explaining the path of the current flowing through each switch module 410 arranged in the X-axis direction. In FIG. 10, the path of the current passing through three switch modules 410 arranged in the X-axis direction is represented by a hollow arrow, a hatched arrow, and a filled arrow, in order from the switch module 410 closest to the smoothing circuit 20.

[0184] As shown in Figures 8 and 9, the smoothing circuit 20, the fuse 30, and the inverter circuit 40 are arranged in sequence from one end to the other end in the longitudinal direction inside the housing 1H (i.e., in the positive direction of the X-axis), as in the first embodiment.

[0185] Moreover, the output terminal 40T is disposed in the center in the longitudinal direction (X-axis direction) inside the housing 1H and in the upper part inside the housing 1H, similarly to the first embodiment. Specifically, the output terminal 40T is disposed above the smoothing circuit 20 and the fuse 30 inside the housing 1H.

[0186] As described above, the output terminal 40T includes a U-phase output terminal 41T, a V-phase output terminal 42T, and a W-phase output terminal 43T. As in the first embodiment, the U-phase output terminal 41T, the V-phase output terminal 42T, and the W-phase output terminal 43T are arranged in order from one end portion in the short side direction inside the housing 1H to the center portion (i.e., in the positive direction of the Y axis).

[0187] As described above, the inverter circuit 40 includes a bridge circuit configured with the U-phase circuit 41, the V-phase circuit 42, and the W-phase circuit 43.

[0188] As shown in Figures 8 and 9, the U-phase circuit 41, the V-phase circuit 42, and the W-phase circuit 43 are arranged in sequence in the Y-axis direction from the end in the negative direction of the Y-axis to the end in the positive direction of the Y-axis, as in the first embodiment.

[0189] The U-phase circuit 41 includes six switch modules 410 (that is, equivalent to the above-mentioned switch modules 411 to 416).

[0190] The six switch modules 410 are arranged in two rows in the Y-axis direction, with two groups of three modules arranged at equal intervals in the X-axis direction. Similarly to the first embodiment, the six switch modules 410 are arranged on another component placed on the bottom surface of the housing 1H.

[0191] As in the first embodiment, the switch module 410 is arranged such that the longitudinal direction in top view is substantially along the X-axis direction. In the switch module 410, an AC output terminal 410O, a negative terminal 410N, and a positive terminal 410P are arranged in order from the side closest to the smoothing circuit 20 (smoothing capacitor 21) along the longitudinal direction (i.e., the X-axis direction).

[0192] As shown in FIGS. 8 and 9, at the upper end of the switch module 410, a U-phase laminated bus bar 41PN is disposed approximately parallel to the X-axis and Y-axis directions, similar to the first embodiment.

[0193] The U-phase laminate bus bar 41PN is disposed over a range covering six switch modules 410 in the X-axis and Y-axis directions.

[0194] 8 and 9, the U-phase AC bus bar 41O connects between the AC output terminal 410O and the U-phase output terminal 41T of the switch module 410. The U-phase AC bus bar 41O includes a U-phase parallel connection bus bar 41O1 and a U-phase output bus bar 41O2, similar to the first embodiment.

[0195] 8 and 9, the U-phase parallel connection bus bar 41O1 is connected to the U-phase output bus bar 41O2 near the switch module 410 that is the farthest from the smoothing circuit 20 among the six switch modules 410 in top view. Specifically, the U-phase parallel connection bus bar 41O1 is connected to the U-phase output bus bar 41O2 at a position farther from the smoothing circuit 20 in the X-axis direction than the end switch module 410 that is farther from the smoothing circuit 20 among a group of three switch modules 410 lined up in the X-axis direction and arranged in two rows in the Y-axis direction in top view.

[0196] More specifically, the U-phase parallel-connection bus bar 41O1 includes six leg portions 41O1a and a connecting portion 41O1b.

[0197] Each of the six legs 41O1a has a flat plate shape that is approximately parallel to the X-axis direction and the Z-axis direction. Each of the six legs 41O1a has a seat portion placed on the AC output terminals 410O of the six switch modules 410, and a main leg portion extending upward (in the positive direction of the Z-axis) from the seat portion. The dimensions of each of the six legs 41O1a in the Z-axis direction are set to be approximately the same. The cross-sectional areas of each of the six legs 41O1a are set to be approximately the same. This makes it possible to make the current densities of each of the six legs 41O1a approximately equal.

[0198] The connecting portion 41O1b has a flat plate shape substantially parallel to the X-axis direction and the Y-axis direction, and connects the six legs 41O1a. Specifically, the connecting portion 41O1b has a substantially rectangular shape in a top view, and is provided so as to extend in the X-axis direction and the Y-axis direction over the range in which the six legs 41O1a are arranged. An end portion in the X-axis positive direction of the connecting portion 41O1b is provided at a position away from the AC output terminals 410O of the two switch modules 410 located at the ends in the X-axis positive direction among the six switch modules 410, and is connected to the U-phase output bus bar 41O2.

[0199] As shown in FIG. 10, the lengths of the paths of the current flowing in the Z-axis direction from the DC input end of the U-phase circuit 41 through the three switch modules 410 arranged in the X-axis direction to the connection part between the U-phase parallel connection bus bar 41O1 and the U-phase output bus bar 41O2 are all approximately equal. This is because, as described above, the dimensions of the six legs 41O1a in the Z-axis direction are approximately equal. In addition, the lengths of the paths of the current flowing in the X-axis direction from the DC input end of the U-phase circuit 41 through the three switch modules 410 arranged in the X-axis direction to the connection part between the U-phase parallel connection bus bar 41O1 and the U-phase output bus bar 41O2 are all approximately equal. This is because the laminate bus bar 20PN, the U-phase laminate bus bar 41PN, and the connecting part 41O1b are arranged approximately parallel to the X-axis direction and the Y-axis direction. Therefore, the entire length of the current path from the DC input end of the U-phase circuit 41 through each of the three switch modules 410 aligned in the X-axis direction to the connection between the U-phase parallel connection bus bar 41O1 and the U-phase output bus bar 41O2 is all approximately equal. The same can be said about the other row of three switch modules 410 aligned in the X-axis direction. Therefore, the entire length of the current path from the smoothing circuit 20 through each of the six switch modules 410 to the U-phase output terminal 41T is all approximately equal. Similarly, the entire length of the current path from the U-phase output terminal 41T through each of the six switch modules 410 to the smoothing circuit 20 is also all approximately equal.

[0200] Further, the cross-sectional area, i.e., the width and thickness, of the connecting portion 41O1b are set so that the current density is approximately equal to that of the U-phase positive side DC bus bar 41P and the U-phase negative side DC bus bar 41N for each of the six power paths passing through each of the six switch modules 410. As a result, the lengths and current densities of the power paths passing through each of the six switch modules 410 between the smoothing circuit 20 and the U-phase output terminal 41T are all approximately equal. Therefore, the inductances of the loop power paths passing through each of the six switch modules 410 between the smoothing circuit 20 and the U-phase output terminal 41T can all be approximately equal and uniform.

[0201] 8 and 9, the U-phase output busbar 41O2 connects the U-phase parallel connection busbar 41O1 and the U-phase output terminal 41T. The U-phase output busbar 41O2 has a folded portion extending upward from the end of the connecting portion 41O1b of the U-phase parallel connection busbar 41O1 in the X-axis positive direction, and a main portion extending from the upper end of the folded portion toward the U-phase output terminal 41T in a manner approximately parallel to the X-axis and Y-axis directions.

[0202] Similar to the U-phase circuit 41, the V-phase circuit 42 includes six switch modules 420 (corresponding to the above-mentioned switch modules 421 to 426).

[0203] The arrangement of the six switch modules 420 is similar to that of the six switch modules 410 of the U-phase circuit 41, and therefore will not be described.

[0204] The switch module 420 is arranged such that its longitudinal direction in top view is substantially along the X-axis direction, similar to the switch module 410. In the switch module 420, an AC output terminal 420O, a negative terminal 420N, and a positive terminal 420P are arranged in order from the side closest to the smoothing circuit 20 (smoothing capacitor 21) along the longitudinal direction (i.e., the X-axis direction).

[0205] At the upper end of the switch module 420, a V-phase laminate bus bar 42PN is disposed substantially parallel to the X-axis direction and the Y-axis direction.

[0206] The V-phase laminate bus bar 42PN is disposed over a range covering six switch modules 420 in the X-axis and Y-axis directions.

[0207] 8 and 9, the V-phase AC bus bar 42O connects between the AC output terminal 420O and the V-phase output terminal 42T of the switch module 420. The V-phase AC bus bar 42O includes a V-phase parallel connection bus bar 42O1 and a V-phase output bus bar 42O2.

[0208] The arrangement and structure of the V-phase AC bus bar 42O are similar to those of the U-phase AC bus bar 41O, and therefore will not be described.

[0209] Like the U-phase circuit 41, the W-phase circuit 43 includes six switch modules 430 (corresponding to the above-mentioned switch modules 431 to 436).

[0210] The arrangement of the six switch modules 430 is similar to that of the six switch modules 410 of the U-phase circuit 41, and therefore will not be described.

[0211] The switch module 430 is disposed so that the longitudinal direction in a top view is substantially along the X-axis direction. In the switch module 430, an AC output terminal 430O, a negative terminal 430N, and a positive terminal 430P are arranged in sequence from the side closest to the smoothing circuit 20 (smoothing capacitor 21) along the longitudinal direction (i.e., the X-axis direction).

[0212] At the upper end of the switch module 430, a W-phase laminate bus bar 43PN is disposed substantially parallel to the X-axis direction and the Y-axis direction.

[0213] The W-phase laminate bus bar 43PN is disposed over a range covering six switch modules 430 in the X-axis and Y-axis directions.

[0214] The detailed structure of the W-phase laminated bus bar 43PN is similar to that of the U-phase laminated bus bar 41PN, and therefore will not be described.

[0215] 8 and 9, the W-phase AC bus bar 43O connects between the AC output terminal 430O and the W-phase output terminal 43T of the switch module 430. The W-phase AC bus bar 43O includes a W-phase parallel connection bus bar 43O1 and a W-phase output bus bar 43O2.

[0216] The arrangement and structure of the W-phase AC bus bar 43O are similar to those of the U-phase AC bus bar 41O, and therefore a description thereof will be omitted.

[0217] Thus, in the second embodiment, the U-phase parallel-connection busbar 41O1 is configured so that the lengths of the power paths between the DC input terminals of the U-phase laminated busbar 41PN and the connection parts with the U-phase output busbar 41O2, which pass through each of the six switch modules 410, are approximately equal. Also, the U-phase parallel-connection busbar 41O1 is configured so that the current densities throughout the power paths between the DC input terminals of the U-phase laminated busbar 41PN and the connection parts with the U-phase output busbar 41O2, which pass through each of the six switch modules 410, are approximately equal. Specifically, the six legs 41O1a have approximately the same length and cross-sectional area, and are configured so that the current densities of each are all approximately equal. The connecting portion 41O1b is configured so that the current density of each of the power paths passing through each of the six switch modules 410 is approximately equal to the current density of the positive side DC bus bar 40P and the negative side DC bus bar 40N. That is, the U-phase parallel connection bus bar 41O1 is configured so that the current densities of the portions (i.e., the six legs 41O1a) where the lengths of the six power paths are common are all approximately equal. The U-phase parallel connection bus bar 41O1 is configured so that the current density of the other portions, i.e., the portions (connecting portion 41O1b) corresponding to the differences in the lengths of the power paths are approximately equal to the current densities of the positive side DC bus bar 40P and the negative side DC bus bar 40N for each of the six power paths. As a result, the lengths and current densities of the loop power paths between the smoothing circuit 20 and the U-phase output terminal 41T passing through each of the six switch modules 410 are all approximately equal. Therefore, it is possible to make the inductance of the loop power path between the smoothing circuit 20 and the U-phase output terminal 41T, which passes through each of the six switch modules 410, approximately equal to each other. Similarly, the V-phase parallel-connection bus bar 42O1 is configured so that the lengths of the power paths between the DC input terminal of the V-phase laminate bus bar 42PN and the connection part with the V-phase output bus bar 42O2, which pass through each of the six switch modules 420, are all approximately equal to each other.The V-phase parallel-connection busbar 42O1 is configured so that the current density is approximately equal throughout the power paths between the DC input terminal of the V-phase laminated busbar 42PN and the connection with the V-phase output busbar 42O2, which pass through each of the six switch modules 420. Therefore, the inductance of the loop power path between the smoothing circuit 20 and the V-phase output terminal 42T, which pass through each of the six switch modules 420, can all be approximately equal and uniform. Similarly, the W-phase parallel-connection busbar 43O1 is configured so that the lengths of the power paths between the DC input terminal of the W-phase laminated busbar 43PN and the connection with the W-phase output busbar 43O2, which pass through each of the six switch modules 430, are all approximately equal. Moreover, the W-phase parallel connection bus bar 43O1 is configured so that the current density is approximately equal throughout each power path between the DC input terminal of the W-phase laminate bus bar 43PN and the connection with the W-phase output bus bar 43O2, which passes through each of the six switch modules 430. Therefore, the inductance of the loop power path between the smoothing circuit 20 and the W-phase output terminal 43T, which passes through each of the six switch modules 430, can all be approximately equal and uniform. Therefore, the imbalance of the currents in the six switch modules 410, the six switch modules 420, and the six switch modules 430 can be suppressed, and the currents can be uniformed.

[0218] In the second embodiment, the number of switch modules 410 connected in parallel may be any number as long as the lengths of the power paths passing through each switch module 410 between the DC input terminal of the U-phase laminated bus bar 41PN and the connection portion with the U-phase output bus bar 41O2 are substantially equal, and the current density throughout each path is configured to be equal. That is, the number of switch modules 410 connected in parallel may be 2 or more and 5 or less, or 7 or more. The number of switch modules 420 and switch modules 430 may be the same. In the second embodiment, the multiple switch modules 410 may be arranged arbitrarily as long as the lengths of the power paths passing through each switch module 410 between the DC input terminal of the U-phase laminated bus bar 41PN and the connection portion with the U-phase output bus bar 41O2 are substantially equal, and the current density throughout each path is configured to be equal. For example, the switch modules 410 may be arranged in a line in the X-axis direction, or a group of one line in the X-axis direction may be arranged in three or more lines in the Y-axis direction. The same may be true for the arrangement of the switch modules 420 and the switch modules 430. In the second embodiment, the U-phase parallel-connection bus bar 41O1 may be configured in any manner as long as the lengths of the power paths passing through each switch module 410 between the DC input terminal of the U-phase laminated bus bar 41PN and the connection portion with the U-phase output bus bar 41O2 are approximately equal, and the current density throughout each path is configured to be equal. For example, the U-phase parallel-connection bus bar 41O1 may be configured such that only the current density of each power path between the connection portions with the leg portions 41O1a at both ends in the X-axis direction of the connection portion 41O1b is approximately equal to that of the U-phase positive-side DC bus bar 41P and the U-phase negative-side DC bus bar 41N. That is, the coupling portion 41O1b of the U-phase parallel-connection bus bar 41O1 may be configured so that the current density of each path section up to the joining of all the paths from each of the six switch modules 410 is substantially equal to that of the U-phase positive-side DC bus bar 41P and the U-phase negative-side DC bus bar 41N. The V-phase parallel-connection bus bar 42O1 and the W-phase parallel-connection bus bar 43O1 may also be configured in the same manner.

[0219] [Third embodiment] Next, a third embodiment will be described with reference to Fig. 11 and Fig. 12. The circuit configuration of the power conversion device 1 according to the third embodiment is similar to that of the above-mentioned second embodiment (Fig. 7), and therefore the description will be omitted. Below, the description will be centered on the parts that are different from the power conversion device 1 according to the first and second embodiments, and the description of the same or corresponding contents as those of the first and second embodiments may be simplified or omitted.

[0220] <Structure of power conversion device> Fig. 11 and Fig. 12 are structural diagrams showing an example of the power conversion device 1 according to the third embodiment. Specifically, Fig. 11 is a perspective view showing a state in which a part of the housing 1H of the power conversion device 1 is removed. Fig. 12 is an exploded perspective view showing a state in which a part of the housing 1H of the power conversion device 1 is removed, and the output terminal 40T, the U-phase output bus bar 41O2, the V-phase output bus bar 42O2, and the W-phase output bus bar 43O2 are removed and moved upward.

[0221] As shown in Figures 11 and 12, the smoothing circuit 20, the fuse 30, and the inverter circuit 40 are arranged in sequence from one end to the other end in the longitudinal direction inside the housing 1H (i.e., in the positive direction of the X-axis), as in the first embodiment, etc.

[0222] Moreover, the output terminal 40T is disposed in the center in the longitudinal direction (X-axis direction) inside the housing 1H and in the upper part inside the housing 1H, similarly to the first embodiment etc. Specifically, the output terminal 40T is disposed above the smoothing circuit 20 and the fuse 30 inside the housing 1H.

[0223] As described above, the output terminals 40T include a U-phase output terminal 41T, a V-phase output terminal 42T, and a W-phase output terminal 43T. As in the first embodiment and the like, the U-phase output terminal 41T, the V-phase output terminal 42T, and the W-phase output terminal 43T are arranged in order from one end portion in the short side direction inside the housing 1H to the center portion (i.e., in the positive direction of the Y axis).

[0224] As described above, the inverter circuit 40 includes a bridge circuit configured with the U-phase circuit 41, the V-phase circuit 42, and the W-phase circuit 43.

[0225] As shown in Figures 11 and 12, the U-phase circuit 41, the V-phase circuit 42, and the W-phase circuit 43 are arranged in sequence in the Y-axis direction from the end in the negative direction of the Y-axis to the end in the positive direction of the Y-axis, as in the first embodiment, etc.

[0226] The U-phase circuit 41 includes six switch modules 410 (that is, equivalent to the above-mentioned switch modules 411 to 416), similarly to the second embodiment.

[0227] The six switch modules 410 are arranged in two rows in the Y-axis direction, with two groups of three modules arranged at equal intervals in the X-axis direction, as in the second embodiment. Also, the six switch modules 410 are arranged on another component placed on the bottom surface of the housing 1H, as in the first embodiment, etc.

[0228] As in the first embodiment, the switch module 410 is arranged such that the longitudinal direction in top view is substantially along the X-axis direction. In the switch module 410, an AC output terminal 410O, a negative terminal 410N, and a positive terminal 410P are arranged in order from the side closest to the smoothing circuit 20 (smoothing capacitor 21) along the longitudinal direction (i.e., the X-axis direction).

[0229] As shown in FIG. 12, at the upper end of the switch module 410, a U-phase laminated bus bar 41PN is disposed approximately parallel to the X-axis and Y-axis directions, similar to the first embodiment and the like.

[0230] The U-phase laminate bus bar 41PN is disposed over a range covering six switch modules 410 in the X-axis and Y-axis directions.

[0231] 12, the U-phase AC bus bar 41O connects between the AC output terminal 410O and the U-phase output terminal 41T of the switch module 410. The U-phase AC bus bar 41O includes a U-phase parallel connection bus bar 41O1 and a U-phase output bus bar 41O2, similar to the first embodiment and the like.

[0232] The U-phase parallel connection busbar 41O1 has a flat plate shape that is approximately parallel to the X-axis and Y-axis directions, and has an approximately rectangular shape covering the six switch modules 410 in top view. The U-phase parallel connection busbar 41O1 is further laminated on the top insulating layer 41I2 (see FIG. 4) of the U-phase laminate busbar 41PN. As a result, the U-phase negative side DC busbar 41N, the U-phase positive side DC busbar 41P, and the U-phase parallel connection busbar 41O1 constitute a U-phase laminate busbar 41PNO having a laminate structure that is laminated from the bottom through the insulating layers 41I1 and 41I2. Therefore, the current density of the U-phase parallel connection busbar 41O1 is approximately equal to that of the U-phase positive side DC busbar 41P and the U-phase negative side DC busbar 41N.

[0233] 11 and 12, the U-phase parallel-connection bus bar 41O1 is provided with relatively large through holes that are substantially rectangular in top view at positions corresponding to the six switch modules 410. This allows the positive terminal 410P (i.e., the through hole for fastening the U-phase positive DC bus bar 41P), the negative terminal 410N (i.e., the through hole for fastening the U-phase negative DC bus bar 41N), and the AC output terminal 410O of the switch module 410 to be exposed in top view. Therefore, an operator can access the positive terminal 410P, the negative terminal 410N, and the AC output terminal 410O of the switch module 410 from above the U-phase parallel-connection bus bar 41O1.

[0234] 11 and 12, the U-phase output busbar 41O2 connects between the U-phase parallel connection busbar 41O1 and the U-phase output terminal 41T. The U-phase output busbar 41O2 is connected to the end of the U-phase parallel connection busbar 41O1 in the X-axis positive direction, that is, to a position farther in the X-axis positive direction than the AC output terminals 410O of the switch modules 410 at the ends of the three switch modules 410 arranged in two rows in the X-axis positive direction. The U-phase output busbar 41O2 is connected to the end of the U-phase parallel connection busbar 41O1 in the X-axis positive direction and at a substantially central position in the Y-axis direction between the AC output terminals 410O of the groups of the three switch modules 410 arranged in two rows in the X-axis direction. As a result, the lengths of the power paths passing through each of the six switch modules 410 between the DC input terminal of the U-phase circuit 41 and the connection portion of the U-phase parallel-connection bus bar 41O1 and the U-phase output bus bar 41O2 are all approximately equal. Therefore, the lengths and current densities of the loop power paths passing through each of the six switch modules 410 between the smoothing circuit 20 and the U-phase output terminal 41T are all approximately equal. Therefore, the inductances of the loop power paths passing through the six switch modules 410 between the smoothing circuit 20 and the U-phase output terminal 41T can be made approximately equal and uniform.

[0235] Similar to the U-phase circuit 41, the V-phase circuit 42 includes six switch modules 420 (corresponding to the above-mentioned switch modules 421 to 426).

[0236] The arrangement of the six switch modules 420 is similar to that of the six switch modules 410 of the U-phase circuit 41, and therefore will not be described.

[0237] The switch module 420 is arranged such that its longitudinal direction in top view is substantially along the X-axis direction, similar to the switch module 410. In the switch module 420, an AC output terminal 420O, a negative terminal 420N, and a positive terminal 420P are arranged in order from the side closest to the smoothing circuit 20 (smoothing capacitor 21) along the longitudinal direction (i.e., the X-axis direction).

[0238] As shown in FIG. 12, at the upper end of the switch module 420, a V-phase laminated bus bar 42PN is disposed substantially parallel to the X-axis direction and the Y-axis direction.

[0239] The V-phase laminate bus bar 42PN is disposed over a range covering six switch modules 420 in the X-axis and Y-axis directions.

[0240] 12, the V-phase AC bus bar 42O connects between the AC output terminal 420O and the V-phase output terminal 42T of the switch module 420. The V-phase AC bus bar 42O includes a V-phase parallel connection bus bar 42O1 and a V-phase output bus bar 42O2.

[0241] The V-phase parallel connection busbar 42O1 has a flat plate shape that is approximately parallel to the X-axis and Y-axis directions, and has an approximately rectangular shape in a top view that covers six switch modules 420. The V-phase parallel connection busbar 42O1 is further laminated on the top insulating layer 42I2 (see FIG. 4) of the V-phase laminate busbar 42PN. As a result, the V-phase negative side DC busbar 42N, the V-phase positive side DC busbar 42P, and the V-phase parallel connection busbar 42O1 constitute a V-phase laminate busbar 42PNO having a laminate structure that is laminated from the bottom through the insulating layers 42I1 and 42I2. Therefore, the current density of the V-phase parallel connection busbar 42O1 is approximately equal to that of the V-phase positive side DC busbar 42P and the V-phase negative side DC busbar 42N.

[0242] The arrangement and structure of the V-phase AC bus bar 42O (the V-phase parallel connection bus bar 42O1 and the V-phase output bus bar 42O2) are similar to those of the U-phase AC bus bar 41O, and therefore will not be described.

[0243] Like the U-phase circuit 41, the W-phase circuit 43 includes six switch modules 430 (corresponding to the above-mentioned switch modules 431 to 436).

[0244] The arrangement of the six switch modules 430 is similar to that of the six switch modules 410 of the U-phase circuit 41, and therefore will not be described.

[0245] The switch module 430 is arranged such that its longitudinal direction in top view is substantially along the X-axis direction, similar to the switch module 410. In the switch module 430, an AC output terminal 430O, a negative terminal 430N, and a positive terminal 430P are arranged in order from the side closest to the smoothing circuit 20 (smoothing capacitor 21) along the longitudinal direction (i.e., the X-axis direction).

[0246] As shown in FIG. 12, at the upper end of the switch module 430, a W-phase laminated bus bar 43PN is disposed substantially parallel to the X-axis direction and the Y-axis direction.

[0247] The W-phase laminate bus bar 43PN is disposed over a range covering six switch modules 430 in the X-axis and Y-axis directions.

[0248] 12, the W-phase AC bus bar 43O connects between the AC output terminal 430O and the W-phase output terminal 43T of the switch module 430. The W-phase AC bus bar 43O includes a W-phase parallel connection bus bar 43O1 and a W-phase output bus bar 43O2.

[0249] The W-phase parallel connection busbar 43O1 has a flat plate shape that is approximately parallel to the X-axis and Y-axis directions, and has an approximately rectangular shape covering the six switch modules 430 in top view. The W-phase parallel connection busbar 43O1 is further laminated on the uppermost insulating layer 43I2 (see FIG. 4) of the W-phase laminate busbar 43PN. As a result, the W-phase negative side DC busbar 43N, the W-phase positive side DC busbar 43P, and the W-phase parallel connection busbar 43O1 constitute a W-phase laminate busbar 43PNO having a laminate structure that is laminated from the bottom through the insulating layers 43I1 and 43I2. Therefore, the current density of the W-phase parallel connection busbar 43O1 is approximately equal to that of the W-phase positive side DC busbar 43P and the W-phase negative side DC busbar 43N.

[0250] The arrangement and structure of the W-phase AC bus bar 43O (the W-phase parallel connection bus bar 43O1 and the W-phase output bus bar 43O2) are similar to those of the U-phase AC bus bar 41O, and therefore a description thereof will be omitted.

[0251] Thus, in the third embodiment, the U-phase parallel connection bus bar 41O1 has a laminate structure in which the U-phase positive side DC bus bar 41P and the U-phase negative side DC bus bar 41N are stacked together with the insulating layers 41I1 and 41I2 interposed therebetween. The U-phase parallel connection bus bar 41O1 is connected to the U-phase output bus bar 41O2 at a position farther in the X-axis positive direction than the AC output terminal 410O of the switch module 410 at the end in the X-axis positive direction among the six switch modules 410. As a result, the lengths and current densities of the looped power paths between the smoothing circuit 20 and the U-phase output terminal 41T passing through each of the six switch modules 410 are all approximately equal. Therefore, the inductances of the looped power paths between the smoothing circuit 20 and the U-phase output terminal 41T passing through each of the six switch modules 410 can be approximately equalized and uniformed. Similarly, the V-phase parallel connection bus bar 42O1 has a laminate structure in which the V-phase positive side DC bus bar 42P and the V-phase negative side DC bus bar 42N are stacked together with insulating layers 42I1 and 42I2 interposed therebetween. The V-phase parallel connection bus bar 42O1 is connected to the V-phase output bus bar 42O2 at a position farther in the X-axis positive direction than the AC output terminal 420O of the switch module 420 at the end in the X-axis positive direction among the six switch modules 420. As a result, the lengths and current densities of the looped power paths between the smoothing circuit 20 and the V-phase output terminal 42T passing through each of the six switch modules 420 are all approximately equal. Therefore, the inductances of the looped power paths between the smoothing circuit 20 and the V-phase output terminal 42T passing through each of the six switch modules 420 can be made approximately equal and uniform. Similarly, the W-phase parallel-connection bus bar 43O1 has a laminate structure in which the W-phase positive-side DC bus bar 43P and the W-phase negative-side DC bus bar 43N are stacked together with insulating layers 43I1, 43I2 interposed between them. The W-phase parallel-connection bus bar 43O1 is connected to the W-phase output bus bar 43O2 at a position farther in the X-axis positive direction than the AC output terminal 430O of the end switch module 430 in the X-axis positive direction among the six switch modules 430.As a result, the lengths and current densities of the looped power paths between the smoothing circuit 20 and the W-phase output terminal 43T that pass through each of the six switch modules 430 are all approximately equal. Therefore, the inductances of the looped power paths between the smoothing circuit 20 and the W-phase output terminal 43T that pass through each of the six switch modules 430 can be approximately equalized and uniformed. Therefore, it is possible to suppress imbalance in the currents of the six switch modules 410, the six switch modules 420, and the six switch modules 430, and to uniform the currents.

[0252] In the third embodiment, the number of switch modules 410 connected in parallel may be any number, and may be 2 or more and 5 or less, or 7 or more. The same may be true for the numbers of switch modules 420 and switch modules 430. In the third embodiment, the arrangement of the multiple switch modules 410 may be any number, and for example, the multiple switch modules 410 may be arranged in one row in the X-axis direction, or a group of one row arranged in the X-axis direction may be arranged in three or more rows in the Y-axis direction.

[0253] [Fourth embodiment] Next, a fourth embodiment will be described with reference to Fig. 13 and Fig. 14. The circuit configuration of the power conversion device 1 according to the fourth embodiment is similar to that of the above-mentioned second embodiment (Fig. 7), and therefore the description will be omitted. Below, the description will be centered on the parts that differ from the power conversion device 1 according to the first to third embodiments, and the description of the same or corresponding contents as the first to third embodiments may be simplified or omitted.

[0254] <Structure of power conversion device> Fig. 13 and Fig. 14 are structural diagrams showing an example of the power conversion device 1 according to the fourth embodiment. Specifically, Fig. 13 is a perspective view showing a state in which a part of the housing 1H of the power conversion device 1 is removed. Fig. 14 is an exploded perspective view showing a state in which a part of the housing 1H of the power conversion device 1 is removed and the output terminal 40T is removed and moved upward.

[0255] As shown in Figures 13 and 14, the smoothing circuit 20, the fuse 30, and the inverter circuit 40 are arranged in sequence from one end to the other end in the longitudinal direction inside the housing 1H (i.e., in the positive direction of the X-axis), as in the first embodiment and the like.

[0256] Moreover, the output terminal 40T is disposed in the center in the longitudinal direction (X-axis direction) inside the housing 1H and in the upper part inside the housing 1H, similarly to the first embodiment etc. Specifically, the output terminal 40T is disposed above the smoothing circuit 20 and the fuse 30 inside the housing 1H.

[0257] As described above, the output terminals 40T include a U-phase output terminal 41T, a V-phase output terminal 42T, and a W-phase output terminal 43T. As in the first embodiment and the like, the U-phase output terminal 41T, the V-phase output terminal 42T, and the W-phase output terminal 43T are arranged in order from one end portion in the short side direction inside the housing 1H to the center portion (i.e., in the positive direction of the Y axis).

[0258] As described above, the inverter circuit 40 includes a bridge circuit configured with the U-phase circuit 41, the V-phase circuit 42, and the W-phase circuit 43.

[0259] As shown in Figures 13 and 14, the U-phase circuit 41, the V-phase circuit 42, and the W-phase circuit 43 are arranged in sequence in the Y-axis direction from the end in the negative direction of the Y-axis to the end in the positive direction of the Y-axis, as in the first embodiment, etc.

[0260] The U-phase circuit 41 includes six switch modules 410 (that is, equivalent to the above-mentioned switch modules 411 to 416), similar to the second embodiment and the like.

[0261] The six switch modules 410 are arranged in two rows in the Y-axis direction, with two groups of three modules arranged at equal intervals in the X-axis direction, as in the second embodiment etc. Also, the six switch modules 410 are arranged on another component placed on the bottom surface of the housing 1H, as in the first embodiment etc.

[0262] As in the first embodiment, the switch module 410 is arranged such that the longitudinal direction in top view is substantially along the X-axis direction. In the switch module 410, an AC output terminal 410O, a negative terminal 410N, and a positive terminal 410P are arranged in order from the side closest to the smoothing circuit 20 (smoothing capacitor 21) along the longitudinal direction (i.e., the X-axis direction).

[0263] As shown in FIGS. 13 and 14, at the upper end of the switch module 410, a U-phase laminated bus bar 41PN is disposed approximately parallel to the X-axis and Y-axis directions, similar to the first embodiment and the like.

[0264] The U-phase laminate bus bar 41PN is disposed over a range covering six switch modules 410 in the X-axis and Y-axis directions.

[0265] 13 and 14, the U-phase AC bus bar 41O connects between the AC output terminal 410O and the U-phase output terminal 41T of the switch module 410. The U-phase AC bus bar 41O includes a U-phase parallel connection bus bar 41O1 and a U-phase output bus bar 41O2, similar to the first embodiment and the like.

[0266] The U-phase parallel connection bus bar 41O1 has a flat plate shape substantially parallel to the X-axis and Y-axis directions, as in the third embodiment, and has a substantially rectangular shape covering the six switch modules 410 in top view. The U-phase parallel connection bus bar 41O1 is further laminated on the top insulating layer 41I2 (see FIG. 4) of the U-phase laminate bus bar 41PN. As a result, the U-phase negative side DC bus bar 41N, the U-phase positive side DC bus bar 41P, and the U-phase parallel connection bus bar 41O1 constitute a laminated structure U-phase laminate bus bar 41PNO that is laminated from the bottom through the insulating layers 41I1 and 41I2. Therefore, the current density of the U-phase parallel connection bus bar 41O1 is substantially equal to that of the U-phase positive side DC bus bar 41P and the U-phase negative side DC bus bar 41N.

[0267] As shown in FIG. 13 and FIG. 14, the U-phase output bus bar 41O2 connects between the U-phase parallel connection bus bar 41O1 and the U-phase output terminal 41T. The U-phase output bus bar 41O2 is connected to the end of the U-phase parallel connection bus bar 41O1 in the negative X-axis direction, that is, to a position farther in the negative X-axis direction than the AC output terminal 410O of the switch module 410 at the end of the three switch modules 410 arranged in the negative X-axis direction in two rows of the three switch modules 410 arranged in the negative X-axis direction. The U-phase output bus bar 41O2 is connected to the end of the U-phase parallel connection bus bar 41O1 in the negative X-axis direction and to a substantially central position in the Y-axis direction between the AC output terminals 410O of the groups of the three switch modules 410 arranged in the negative X-axis direction in two rows of the three switch modules 410. As a result, the direction of the current flowing through the U-phase positive side DC bus bar 41P toward each of the six switch modules 410 is the positive X-axis direction. On the other hand, the direction of the current flowing through the U-phase parallel connection bus bar 41O1 from each of the six switch modules 410 toward the U-phase output terminal 41T is the opposite, negative direction of the X-axis. Therefore, by currents of the same current density flowing in the opposite directions, the magnetic fields generated by the currents of the U-phase positive side DC bus bar 41P and the U-phase parallel connection bus bar 41O1 are offset, and the inductance can be significantly reduced. Similarly, the direction of the current flowing through the U-phase parallel connection bus bar 41O1 from the U-phase output terminal 41T toward each of the six switch modules 410 is the positive direction of the X-axis. On the other hand, the direction of the current flowing through the U-phase negative side DC bus bar 41N from each of the six switch modules 410 toward the smoothing circuit 20 is the negative direction of the X-axis. Therefore, by currents of the same magnitude flowing in opposite directions, the magnetic fields generated by the currents in the U-phase negative-side DC bus bar 41N and the U-phase parallel-connection bus bar 41O1 are offset, and the inductance can be significantly reduced. Therefore, the inductance of each of the loop power paths between the smoothing circuit 20 and the U-phase output terminal 41T passing through the six switch modules 410 becomes very small, thereby suppressing the difference in inductance between the power paths and making the inductance uniform.

[0268] Similar to the U-phase circuit 41, the V-phase circuit 42 includes six switch modules 420 (corresponding to the above-mentioned switch modules 421 to 426).

[0269] The arrangement of the six switch modules 420 is similar to that of the six switch modules 410 of the U-phase circuit 41, and therefore will not be described.

[0270] The switch module 420 is arranged such that its longitudinal direction in top view is substantially along the X-axis direction, similar to the switch module 410. In the switch module 420, an AC output terminal 420O, a negative terminal 420N, and a positive terminal 420P are arranged in order from the side closest to the smoothing circuit 20 (smoothing capacitor 21) along the longitudinal direction (i.e., the X-axis direction).

[0271] As shown in FIGS. 13 and 14, at the upper end of the switch module 420, a V-phase laminated bus bar 42PN is disposed substantially parallel to the X-axis direction and the Y-axis direction.

[0272] The V-phase laminate bus bar 42PN is disposed over a range covering six switch modules 420 in the X-axis and Y-axis directions.

[0273] 13 and 14, the V-phase AC bus bar 42O connects between the AC output terminal 420O and the V-phase output terminal 42T of the switch module 420. The V-phase AC bus bar 42O includes a V-phase parallel connection bus bar 42O1 and a V-phase output bus bar 42O2.

[0274] The V-phase parallel connection busbar 42O1 has a flat plate shape substantially parallel to the X-axis and Y-axis directions, as in the third embodiment, and has a substantially rectangular shape covering the six switch modules 420 in top view. The V-phase parallel connection busbar 42O1 is further laminated on the top insulating layer 42I2 (see FIG. 4) of the V-phase laminate busbar 42PN. As a result, the V-phase negative side DC busbar 42N, the V-phase positive side DC busbar 42P, and the V-phase parallel connection busbar 42O1 constitute a V-phase laminate busbar 42PNO having a laminate structure laminated in order from the bottom through the insulating layers 42I1 and 42I2. Therefore, the current density of the V-phase parallel connection busbar 42O1 is substantially equal to that of the V-phase positive side DC busbar 42P and the V-phase negative side DC busbar 42N.

[0275] The arrangement and structure of the V-phase AC bus bar 42O (the V-phase parallel connection bus bar 42O1 and the V-phase output bus bar 42O2) are similar to those of the U-phase AC bus bar 41O, and therefore will not be described.

[0276] Like the U-phase circuit 41, the W-phase circuit 43 includes six switch modules 430 (corresponding to the above-mentioned switch modules 431 to 436).

[0277] The arrangement of the six switch modules 430 is similar to that of the six switch modules 410 of the U-phase circuit 41, and therefore will not be described.

[0278] The switch module 430 is arranged such that its longitudinal direction in top view is substantially along the X-axis direction, similar to the switch module 410. In the switch module 430, an AC output terminal 430O, a negative terminal 430N, and a positive terminal 430P are arranged in order from the side closest to the smoothing circuit 20 (smoothing capacitor 21) along the longitudinal direction (i.e., the X-axis direction).

[0279] As shown in FIGS. 13 and 14, at the upper end of the switch module 430, a W-phase laminated bus bar 43PN is disposed substantially parallel to the X-axis direction and the Y-axis direction.

[0280] The W-phase laminate bus bar 43PN is disposed over a range covering six switch modules 430 in the X-axis and Y-axis directions.

[0281] 13 and 14, the W-phase AC bus bar 43O connects between the AC output terminal 430O and the W-phase output terminal 43T of the switch module 430. The W-phase AC bus bar 43O includes a W-phase parallel connection bus bar 43O1 and a W-phase output bus bar 43O2.

[0282] The W-phase parallel connection bus bar 43O1 has a flat plate shape substantially parallel to the X-axis and Y-axis directions, as in the third embodiment, and has a substantially rectangular shape covering the six switch modules 430 in top view. The W-phase parallel connection bus bar 43O1 is further laminated on the uppermost insulating layer 43I2 (see FIG. 4) of the W-phase laminate bus bar 43PN. As a result, the W-phase negative side DC bus bar 43N, the W-phase positive side DC bus bar 43P, and the W-phase parallel connection bus bar 43O1 constitute a W-phase laminate bus bar 43PNO having a laminate structure laminated in order from the bottom through the insulating layers 43I1 and 43I2. Therefore, the current density of the W-phase parallel connection bus bar 43O1 is substantially equal to that of the W-phase positive side DC bus bar 43P and the W-phase negative side DC bus bar 43N.

[0283] The arrangement and structure of the W-phase AC bus bar 43O (the W-phase parallel connection bus bar 43O1 and the W-phase output bus bar 43O2) are similar to those of the U-phase AC bus bar 41O, and therefore a description thereof will be omitted.

[0284] Thus, in the fourth embodiment, the U-phase parallel connection busbar 41O1 has a laminate structure in which the U-phase positive side DC busbar 41P and the U-phase negative side DC busbar 41N are stacked together with the insulating layers 41I1, 41I2 interposed therebetween. The U-phase parallel connection busbar 41O1 is connected to the U-phase output busbar 41O2 at a position farther in the X-axis negative direction than the AC output terminal 410O of the switch module 410 at the end in the X-axis negative direction among the six switch modules 410. As a result, the currents in the U-phase positive side DC busbar 41P and the U-phase parallel connection busbar 41O1 and the currents in the U-phase parallel connection busbar 41O1 and the U-phase negative side DC busbar 41N before and after passing through each of the six switch modules 410 have the same current density and flow in opposite directions in space. Therefore, the magnetic fields generated by the currents of the U-phase positive side DC busbar 41P and the U-phase parallel connection busbar 41O1 and the currents of the U-phase parallel connection busbar 41O1 and the U-phase negative side DC busbar 41N are offset, and the inductance of these power paths can be made very small. As a result, the difference in inductance between the loop power paths between the smoothing circuit 20 and the U-phase output terminal 41T passing through each of the six switch modules 410 is suppressed, and the inductance can be made uniform. Similarly, the V-phase parallel connection busbar 42O1 has a laminate structure in which the V-phase positive side DC busbar 42P and the V-phase negative side DC busbar 42N are stacked together with insulating layers 42I1 and 42I2 interposed between them. Moreover, the V-phase parallel connection busbar 42O1 is connected to the V-phase output busbar 42O2 at a position farther in the X-axis negative direction than the AC output terminal 420O of the switch module 420 at the end in the X-axis negative direction among the six switch modules 420. As a result, the currents in the V-phase positive side DC busbar 42P and the V-phase parallel connection busbar 42O1, and the currents in the V-phase parallel connection busbar 42O1 and the V-phase negative side DC busbar 42N before and after passing through each of the six switch modules 420 have the same current density and are directed in opposite directions in space. Therefore, the magnetic fields generated by the currents in the V-phase positive side DC busbar 42P and the V-phase parallel connection busbar 42O1, and the currents in the V-phase parallel connection busbar 42O1 and the V-phase negative side DC busbar 42N are offset, and the inductance of these power paths can be made very small.As a result, the difference in inductance between the loop power paths between the smoothing circuit 20 and the V-phase output terminal 42T passing through each of the six switch modules 420 can be suppressed, and the inductance can be made uniform. Similarly, the W-phase parallel-connection bus bar 43O1 has a laminate structure in which the W-phase positive-side DC bus bar 43P and the W-phase negative-side DC bus bar 43N are stacked together with insulating layers 43I1 and 43I2 interposed therebetween. The W-phase parallel-connection bus bar 43O1 is connected to the W-phase output bus bar 43O2 at a position farther in the X-axis negative direction than the AC output terminal 430O of the switch module 430 at the end of the six switch modules 430 in the X-axis negative direction. As a result, the currents of the W-phase positive side DC busbar 43P and the W-phase parallel connection busbar 43O1, and the currents of the W-phase parallel connection busbar 43O1 and the W-phase negative side DC busbar 43N before and after passing through each of the six switch modules 430 have the same current density and are directed in opposite directions in space. Therefore, the magnetic fields generated by the currents of the W-phase positive side DC busbar 43P and the W-phase parallel connection busbar 43O1, and the currents of the W-phase parallel connection busbar 43O1 and the W-phase negative side DC busbar 43N are offset, and the inductance of these power paths can be made very small. As a result, the difference in inductance between the paths of the loop power path between the smoothing circuit 20 and the W-phase output terminal 43T that passes through each of the six switch modules 430 can be suppressed, and the inductance can be made uniform. Therefore, it is possible to suppress imbalance in the currents of the six switch modules 410, the six switch modules 420, and the six switch modules 430, and to equalize the currents.

[0285] In the fourth embodiment, the number of switch modules 410 connected in parallel may be any number, and may be 2 or more and 5 or less, or 7 or more. The same may be true for the numbers of switch modules 420 and switch modules 430. In the fourth embodiment, the arrangement of the multiple switch modules 410 may be any number, and for example, the multiple switch modules 410 may be arranged in one row in the X-axis direction, or a group of one row arranged in the X-axis direction may be arranged in three or more rows in the Y-axis direction.

[0286] [Effect] Next, the operation of the power conversion device 1 according to this embodiment will be described.

[0287] In this embodiment (first embodiment), the power conversion device 1 includes a smoothing circuit 20, an inverter circuit 40, and an output terminal 40T. Specifically, the inverter circuit 40 includes a U-phase circuit 41 configured by connecting a plurality of switch modules 410 in parallel, each of which has an upper and lower arm connected in series, each of which includes a plurality of semiconductor switches 410s, and connecting the connection points (AC output terminals 410O) of the upper and lower arms of each of the plurality of switch modules 410 to each other. Similarly, the inverter circuit 40 includes a V-phase circuit 42 configured by connecting a plurality of switch modules 420 in parallel, each of which has an upper and lower arm connected in series, each of which includes a plurality of semiconductor switches 420s, and connecting the connection points (AC output terminals 420O) of the upper and lower arms of each of the plurality of switch modules 420 to each other. Similarly, the inverter circuit 40 includes a W-phase circuit 43 configured by connecting a plurality of switch modules 430 in parallel, each of which has upper and lower arms connected in series, each of which includes a plurality of semiconductor switches 430s, and connecting the connection points (AC output terminals 430O) of the upper and lower arms of each of the plurality of switch modules 430 together. That is, the inverter circuit 40 includes a bridge circuit configured by connecting output circuits (U-phase circuit 41, V-phase circuit 42, and W-phase circuit 43) in parallel for a plurality of phases. The inverter circuit 40 outputs a predetermined AC power based on the DC power input from the smoothing circuit 20. The output terminal 40T outputs the predetermined AC power from the inverter circuit 40 to the outside. The inverter circuit 40 also includes a positive DC bus bar 40P that connects the positive terminals 410P, 420P, and 430P of the multiple switch modules 410, 420, and 430 together, and a negative DC bus bar 40N that connects the negative terminals 410N, 420N, and 430N of the multiple switch modules 410, 420, and 430 together. The inverter circuit 40 also includes a U-phase parallel connection bus bar 41O1 that connects the AC output terminals 410O of the multiple switch modules 410 together. Similarly, the inverter circuit 40 includes a V-phase parallel connection bus bar 42O1 that connects the AC output terminals 420O of the multiple switch modules 420 together. Similarly, the inverter circuit 40 includes a W-phase parallel connection bus bar 43O1 that connects the AC output terminals 430O of the multiple switch modules 430 together.The positive-side DC busbar 40P and the negative-side DC busbar 40N have a laminate structure in which they are laminated with insulating layers 41I1, 42I1, and 43I1 interposed therebetween. The U-phase parallel connection busbar 41O1 is configured so that the lengths of the paths between all the arms (semiconductor switches 410s) included in the multiple switch modules 410 and the junction where all the paths from each of the multiple switch modules 410 join are approximately equal. Similarly, the V-phase parallel connection busbar 42O1 is configured so that the lengths of the paths between all the arms (semiconductor switches 420s) included in the multiple switch modules 420 and the junction where all the paths from each of the multiple switch modules 420 join are approximately equal. Similarly, the W-phase parallel connection busbar 43O1 is configured so that the lengths of the paths between all the arms (semiconductor switches 430s) included in the multiple switch modules 430 and the junction where all the paths from each of the multiple switch modules 430 join are approximately equal.

[0288] For example, in an inverter circuit, the current capacity of the power conversion device can be increased by connecting multiple switch legs in parallel.

[0289] In this case, if the inductance of each path passing through the multiple switch legs is different, an imbalance in the current passing through the multiple switch legs may occur, causing current concentration in the semiconductor switches included in some of the switch legs, which may result in damage to the semiconductor switch elements due to temperature rise caused by loss.

[0290] On the other hand, it is also possible to determine the current capacity of the power conversion device by considering the current imbalance by matching the allowable current of the semiconductor switch where the most current is concentrated. However, in this case, only a current relatively lower than the allowable current flows through the semiconductor switches other than the semiconductor switch where the current is concentrated. As a result, even if the number of switch legs connected in parallel is increased, the allowable current of the entire plurality of switch legs cannot be effectively used, and it is possible that the current capacity of the power conversion device cannot be increased significantly.

[0291] In contrast, in this embodiment (first embodiment), the positive-side DC bus bar 40P and the negative-side DC bus bar 40N are laminated to make the inductance of the DC wiring portion on the positive and negative sides of the inverter circuit 40 very small. Therefore, the inductance of the AC wiring portion is dominant in the inductance of the loop of the power path between the smoothing circuit 20 and the output terminal 40T. In addition, the lengths of the paths from all the arms (semiconductor switches 410s) included in the multiple switch modules 410 to the junction are configured to be approximately equal, so that the difference in inductance of the power path passing through each semiconductor switch 410s in the U-phase parallel connection bus bar 41O1 can be relatively small. Therefore, the power conversion device 1 can relatively small the difference in inductance of the loop of the power path between the smoothing circuit 20 and the output terminal 40T (U-phase output terminal 41T) for the power path passing through each of the multiple switch modules 410. Therefore, the power conversion device 1 can suppress the imbalance of the currents of the multiple semiconductor switches 410s (switch modules 410) and achieve the equalization of the currents. The same applies to the multiple switch modules 420. Therefore, the power conversion device 1 can relatively reduce the difference in inductance of the loop of the power path between the smoothing circuit 20 and the output terminal 40T (V-phase output terminal 42T) for the power path passing through each of the multiple switch modules 420. Therefore, the power conversion device 1 can suppress the imbalance of the currents of the multiple semiconductor switches 420s (switch modules 420) and achieve the equalization of the currents. The same applies to the multiple switch modules 430. Therefore, the power conversion device 1 can relatively reduce the difference in inductance of the loop of the power path between the smoothing circuit 20 and the output terminal 40T (W-phase output terminal 43T) for the power path passing through each of the multiple switch modules 430. Therefore, the power conversion device 1 can suppress imbalance in the currents of the multiple semiconductor switches 430s (switch modules 430) and equalize the currents.

[0292] Furthermore, in this embodiment (first embodiment), the U-phase parallel-connection bus bar 41O1 is configured so that the current density of each path between all the semiconductor switches 410s included in the multiple switch modules 410 and a junction where all the paths from each of the multiple switch modules 410 join together is approximately equal. The same may be true for the V-phase parallel-connection bus bar 42O1 and the W-phase parallel-connection bus bar 43O1.

[0293] This allows the inductance of the power paths passing through each semiconductor switch 410s in the U-phase parallel-connection bus bar 41O1 to be approximately equal. Therefore, the power conversion device 1 can make the inductance of the loop power path between the smoothing circuit 20 and the output terminal 40T (U-phase output terminal 41T) approximately equal for the power paths passing through each of the multiple switch modules 410. Therefore, the power conversion device 1 can further suppress the imbalance of the currents of the multiple semiconductor switches 410s (switch modules 410) and further equalize the currents. The same action and effect is also achieved for the V-phase parallel-connection bus bar 42O1 and the W-phase parallel-connection bus bar 43O1.

[0294] In this embodiment (first embodiment), two switch modules 410 included in the multiple switch modules 410 are arranged side by side in one axial direction (X-axis direction). The same may be true for the multiple switch modules 420 and the multiple switch modules 430. The U-phase parallel connection bus bar 41O1 may join paths from the two switch modules 410 toward the U-phase output terminal 41T at a substantially central position (midpoint) between the AC output terminals 410O of the two switch modules 410 in the X-axis direction. The same may be true for the V-phase parallel connection bus bar 42O1 and the W-phase parallel connection bus bar 43O1.

[0295] As a result, the U-phase parallel-connection bus bar 41O1 can merge the paths from the AC output terminals 410O of the two switch modules 410 so that the paths have approximately the same length for each combination of two switch modules 410. The V-phase parallel-connection bus bar 42O1 and the W-phase parallel-connection bus bar 43O1 also have the same effects.

[0296] In the present embodiment (first embodiment), the multiple switch modules 410 connected in parallel may include multiple combinations of two switch modules 410. The same may be true for the multiple switch modules 420 connected in parallel and the multiple switch modules 430 connected in parallel. The U-phase parallel-connection bus bar 41O1 may be configured so that the lengths of the power paths between an intermediate junction where paths from each of the two switch modules 410 for each of the multiple combinations join and a junction where paths from each of all the switch modules 410 join are approximately equal. The same may be true for the V-phase parallel-connection bus bar 42O1 and the W-phase parallel-connection bus bar 43O1.

[0297] This allows the lengths of the paths from each of the multiple switch modules 410 connected in parallel to be approximately equalized in the U-phase parallel-connection bus bar 41O1 until they join together. The same effects and advantages are also achieved for the V-phase parallel-connection bus bar 42O1 and the W-phase parallel-connection bus bar 43O1.

[0298] In the present embodiment (first embodiment), the multiple (four) switch modules 410 connected in parallel may be arranged in two rows in another axis direction (Y axis direction) perpendicular to the X axis direction, with two switch modules 410 in two sets aligned in the X axis direction. The multiple (four) switch modules 420 and the multiple (four) switch modules 430 may be arranged in the same manner. The U-phase parallel connection bus bar 41O1 is configured to be substantially symmetrical with respect to a vertical plane at the center position of the two switch modules 410 in the X axis direction. The U-phase parallel connection bus bar 41O1 may be configured to be substantially symmetrical with respect to a vertical plane at the center position of the two sets in the Y axis direction. The U-phase parallel connection bus bar 41O1 may be configured such that a connection portion with a wiring (U-phase output bus bar 41O2) to the U-phase output terminal 41T is located at the center position between the four switch modules 410 included in the two sets in the X axis direction and the Y axis direction. The same may be true for the V-phase parallel connection bus bar 42O1 and the W-phase parallel connection bus bar 43O1.

[0299] As a result, in the U-phase parallel-connection bus bar 41O1, specifically, the lengths of the paths of the multiple (four) switch modules 410 connected in parallel to the junction can be made substantially equal. Therefore, in the power conversion device 1, specifically, the inductance of the paths passing through each semiconductor switch 410s can be made substantially equal. The same effects and advantages are also achieved for the V-phase parallel-connection bus bar 42O1 and the W-phase parallel-connection bus bar 43O1.

[0300] In the present embodiment (second embodiment), the power conversion device 1 includes a smoothing circuit 20, an inverter circuit 40, and an output terminal 40T. Specifically, the inverter circuit 40 includes a U-phase circuit 41 configured by connecting a plurality of switch modules 410 in parallel, each of which has an upper and lower arm connected in series, each of which includes a plurality of semiconductor switches 410s, and connecting the connection points (AC output terminals 410O) of the upper and lower arms of each of the plurality of switch modules 410 to each other. Similarly, the inverter circuit 40 includes a V-phase circuit 42 configured by connecting a plurality of switch modules 420 in parallel, each of which has an upper and lower arm connected in series, each of which includes a plurality of semiconductor switches 420s, and connecting the connection points (AC output terminals 420O) of the upper and lower arms of each of the plurality of switch modules 420 to each other. Similarly, the inverter circuit 40 includes a W-phase circuit 43 configured by connecting a plurality of switch modules 430 in parallel, each of which has upper and lower arms connected in series, each of which includes a plurality of semiconductor switches 430s, and connecting the connection points (AC output terminals 430O) of the upper and lower arms of each of the plurality of switch modules 430 together. That is, the inverter circuit 40 includes a bridge circuit configured by connecting output circuits (U-phase circuit 41, V-phase circuit 42, and W-phase circuit 43) in parallel for a plurality of phases. The inverter circuit 40 outputs a predetermined AC power based on the DC power input from the smoothing circuit 20. The output terminal 40T outputs the predetermined AC power from the inverter circuit 40 to the outside. The inverter circuit 40 also includes a positive-side DC bus bar 40P that connects the positive terminals 410P, 420P, 430P of the multiple switch modules 410, 420, 430 together, and a negative-side DC bus bar 40N that connects the negative terminals 410N, 420N, 430N of the multiple switch modules 410, 420, 430 together. The inverter circuit 40 also includes a U-phase parallel connection bus bar 41O1 that connects the AC output terminals 410O of the multiple switch modules 410 together. Similarly, the inverter circuit 40 includes a V-phase parallel connection bus bar 42O1 that connects the AC output terminals 420O of the multiple switch modules 420 together.Similarly, the inverter circuit 40 includes a W-phase parallel connection bus bar 43O1 that connects the AC output terminals 430O of the multiple switch modules 430. The positive side DC bus bar 40P and the negative side DC bus bar 40N have a laminate structure in which they are stacked via insulating layers 41I1, 42I1, and 43I1. The U-phase parallel connection bus bar 41O1 is configured so that the lengths of the power paths between the smoothing circuit 20 and the junction where the paths from the multiple switch modules 410 join, which pass through all the arms (semiconductor switches 410s) included in the multiple switch modules 410, are approximately equal. The U-phase parallel connection bus bar 41O1 is configured so that the current density over the entire path of each power path between the smoothing circuit 20 and the junction, which pass through all the arms included in the multiple switch modules 410, is approximately equal. Similarly, the V-phase parallel connection busbar 42O1 is configured so that the lengths of the power paths passing through all the arms (semiconductor switches 420s) included in the multiple switch modules 420 between the smoothing circuit 20 and the junction where the paths from each of the multiple switch modules 420 join are approximately equal. The V-phase parallel connection busbar 42O1 is configured so that the current density over the entire path of each power path passing through all the arms included in the multiple switch modules 420 between the smoothing circuit 20 and the junction is approximately equal. Similarly, the W-phase parallel connection busbar 43O1 is configured so that the lengths of the power paths passing through all the arms (semiconductor switches 430s) included in the multiple switch modules 430 to the junction where the paths from the smoothing circuit 20 and each of the multiple switch modules 430 join are approximately equal. The W-phase parallel connection bus bar 43O1 is configured so that the current density throughout the entire path of each power path between the smoothing circuit 20 and the above-mentioned junction, passing through each of all the arms included in the multiple switch modules 430, is approximately equal.

[0301] This makes it possible to equalize the lengths of all the paths between the junctions of the DC input and the AC output in the inverter circuit 40 and the current density over the entire path. Therefore, the power conversion device 1 can make the inductance of the loop of the power path between the smoothing circuit 20 and the output terminal 40T (U-phase output terminal 41T) approximately equal for the power paths passing through each of the multiple switch modules 410. Therefore, the power conversion device 1 can suppress the imbalance of the currents of the multiple semiconductor switches 410s (switch modules 410) and equalize the currents. The same is true for the multiple switch modules 420. Therefore, the power conversion device 1 can make the inductance of the loop of the power path between the smoothing circuit 20 and the output terminal 40T (V-phase output terminal 42T) approximately equal for the power paths passing through each of the multiple switch modules 420. Therefore, the power conversion device 1 can suppress the imbalance of the currents of the multiple semiconductor switches 420s (switch modules 420) and equalize the currents. The same is true for the multiple switch modules 430. Therefore, the power conversion device 1 can make the inductance of the loop power path between the smoothing circuit 20 and the output terminal 40T (W-phase output terminal 43T) approximately equal for the power path passing through each of the multiple switch modules 430. Therefore, the power conversion device 1 can suppress imbalance in the currents of the multiple semiconductor switches 430s (switch modules 430) and equalize the currents.

[0302] In this embodiment (second embodiment), the U-phase parallel connection bus bar 41O1 may be configured so that the current densities of the portions of the power paths passing through the multiple switch modules 410 that have a common length are substantially equal. The U-phase parallel connection bus bar 41O1 may be configured so that the current densities of the other portions, i.e., portions corresponding to the difference in length of the power paths, are substantially equal to the current densities of the positive side DC bus bar 40P and the negative side DC bus bar 40N for each power path. The same may be true for the V-phase parallel connection bus bar 42O1 and the W-phase parallel connection bus bar 43O1.

[0303] This makes it possible to make the current density in the inverter circuit 40 approximately equal over the entire path for each path between the junction of the DC input and the AC input.

[0304] In the present embodiment (second embodiment), the smoothing circuit 20 and the inverter circuit 40 may be arranged side by side in one axial direction (X-axis direction). The multiple switch modules 410 may be arranged side by side in the X-axis direction. The multiple switch modules 420 and the multiple switch modules 430 may be arranged in the same manner. The U-phase parallel-connection bus bar 41O1 may include multiple legs 41O1a extending in the vertical direction (Z-axis direction) from connection points (AC output terminals 410O) of the upper and lower arms of each of the multiple switch modules 410 and having substantially the same length and cross-sectional area. The U-phase parallel-connection bus bar 41O1 may include a connecting portion 41O1b connecting the multiple legs 41O1a to each other so as to extend in the X-axis direction. The connecting portion 41O1b may be connected to a wiring (U-phase output bus bar 41O2) leading to the output terminal 40T (U-phase output terminal 41T) at an end portion farther from the smoothing circuit 20 in the X-axis direction. The connecting portion 41O1b may be configured so that the current density of each power path passing through each of the multiple switch modules 410 is approximately equal to the current density of the positive side DC bus bar 40P and the negative side DC bus bar 40N. The same may be true for the V-phase parallel connection bus bar 42O1 and the W-phase parallel connection bus bar 43O1.

[0305] This makes it possible to make the lengths of all the power paths between the junction of the DC input and the AC output in the inverter circuit 40 and the current density throughout each of the power paths approximately equal.

[0306] In this embodiment (second embodiment), the multiple switch modules 410 may be arranged such that two groups aligned in one axial direction (X-axis direction) are aligned in two rows in another axial direction (Y-axis direction) perpendicular to the X-axis direction. The connecting portion 41O1b of the U-phase parallel connection bus bar 41O1 may connect the multiple leg portions 41O1a to each other so as to extend in the X-axis direction and the Y-axis direction.

[0307] This makes it possible to make the lengths of all the power paths between the junction of the DC input and the AC output in the inverter circuit 40 and the current density throughout each of the power paths approximately equal.

[0308] In the present embodiment (third embodiment), the power conversion device 1 includes a smoothing circuit 20, an inverter circuit 40, and an output terminal 40T. Specifically, the inverter circuit 40 includes a U-phase circuit 41 configured by connecting a plurality of switch modules 410 in parallel, each of which has an upper and lower arm connected in series, each of which includes a plurality of semiconductor switches 410s, and connecting the connection points (AC output terminals 410O) of the upper and lower arms of each of the plurality of switch modules 410 to each other. Similarly, the inverter circuit 40 includes a V-phase circuit 42 configured by connecting a plurality of switch modules 420 in parallel, each of which has an upper and lower arm connected in series, each of which includes a plurality of semiconductor switches 420s, and connecting the connection points (AC output terminals 420O) of the upper and lower arms of each of the plurality of switch modules 420 to each other. Similarly, the inverter circuit 40 includes a W-phase circuit 43 configured by connecting a plurality of switch modules 430 in parallel, each of which has upper and lower arms connected in series, each of which includes a plurality of semiconductor switches 430s, and connecting the connection points (AC output terminals 430O) of the upper and lower arms of each of the plurality of switch modules 430 together. That is, the inverter circuit 40 includes a bridge circuit configured by connecting output circuits (U-phase circuit 41, V-phase circuit 42, and W-phase circuit 43) in parallel for a plurality of phases. The inverter circuit 40 outputs a predetermined AC power based on the DC power input from the smoothing circuit 20. The output terminal 40T outputs the predetermined AC power from the inverter circuit 40 to the outside. The inverter circuit 40 also includes a positive DC bus bar 40P that connects the positive terminals 410P, 420P, 430P of the multiple switch modules 410, 420, 430, and a negative DC bus bar 40N that connects the negative terminals 410N, 420N, 430N of the multiple switch modules 410, 420, 430. The inverter circuit 40 also includes a U-phase parallel connection bus bar 41O1 that connects the AC output terminals 410O of the multiple switch modules 410. The positive DC bus bar 40P, the negative DC bus bar 40N, and the U-phase parallel connection bus bar 41O1 have a laminate structure in which they are stacked with insulating layers 41I1, 41I2 interposed therebetween.Similarly, the inverter circuit 40 includes a V-phase parallel connection bus bar 42O1 that connects the AC output terminals 420O of the multiple switch modules 420 together. The positive DC bus bar 40P, the negative DC bus bar 40N, and the V-phase parallel connection bus bar 42O1 have a laminate structure in which they are stacked with insulating layers 42I1 and 42I2 interposed therebetween. Similarly, the inverter circuit 40 includes a W-phase parallel connection bus bar 43O1 that connects the AC output terminals 430O of the multiple switch modules 430 together. The positive DC bus bar 40P, the negative DC bus bar 40N, and the W-phase parallel connection bus bar 43O1 have a laminate structure in which they are stacked with insulating layers 43I1 and 43I2 interposed therebetween. A connection portion between the U-phase parallel connection bus bar 41O1 and the wiring (U-phase output bus bar 41O2) to the output terminal 40T (U-phase output terminal 41T) is provided at a position farther from the smoothing circuit 20 than the semiconductor switch 410s that is farthest from the smoothing circuit 20 among all the arms (semiconductor switches 410s) included in the multiple switch modules 410. Similarly, a connection portion between the V-phase parallel connection bus bar 42O1 and the wiring to the output terminal 40T (V-phase output terminal 42T) is provided at a position farther from the smoothing circuit 20 than the semiconductor switch 420s that is farthest from the smoothing circuit 20 among all the arms (semiconductor switches 420s) included in the multiple switch modules 420. Similarly, the connection portion between the W-phase parallel connection bus bar 43O1 and the wiring to the output terminal 40T (W-phase output terminal 43T) is provided at a position farther from the smoothing circuit 20 than the semiconductor switch 430s that is farthest from the smoothing circuit 20 among all the arms (semiconductor switches 430s) included in the multiple switch modules 430.

[0309] As a result, the busbars of the inverter circuit 40 are laminated to substantially equalize the current density of all the power paths between the junctions of the DC input and AC input of the inverter circuit 40. In addition, the junctions where the paths from each of the switch modules 410 join are set near the semiconductor switch 410s that is the furthest from the smoothing circuit 20, due to the arrangement of the connection between the U-phase parallel connection busbar 41O1 and the U-phase output busbar 41O2. That is, the lengths of all the power paths between the junctions of the DC input and AC output in the inverter circuit 40 that pass through each of the switch modules 410 can be substantially equalized. Therefore, the power conversion device 1 can substantially equalize the inductances of all the loop power paths between the smoothing circuit 20 and the output terminal 40T (U-phase output terminal 41T) that pass through each of the switch modules 410. Therefore, the power conversion device 1 can suppress the imbalance of the currents of the semiconductor switches 410s (switch modules 410) and equalize the currents. The same applies to the multiple switch modules 420. Therefore, the power conversion device 1 can make all the inductances of the loop power paths between the smoothing circuit 20 and the output terminal 40T (V-phase output terminal 42T) that pass through each of the multiple switch modules 420 approximately equal. Therefore, the power conversion device 1 can suppress the imbalance of the currents of the multiple semiconductor switches 420s (switch modules 420) and achieve uniformity of the currents. The same applies to the multiple switch modules 430. Therefore, the power conversion device 1 can make all the inductances of the loop power paths between the smoothing circuit 20 and the output terminal 40T (W-phase output terminal 43T) that pass through each of the multiple switch modules 430 approximately equal. Therefore, the power conversion device 1 can suppress the imbalance of the currents of the multiple semiconductor switches 430s (switch modules 430) and achieve uniformity of the currents.

[0310] In this embodiment (third embodiment), the smoothing circuit 20 and the inverter circuit 40 may be arranged side by side in one axial direction (X-axis direction). A connection portion between the U-phase parallel connection bus bar 41O1 and the U-phase output bus bar 41O2 may be arranged in a position farther from the smoothing circuit 20 in the X-axis direction than the switch module 410 farthest from the smoothing circuit 20 among the multiple switch modules 410. The same may be true for the connection portion between the V-phase parallel connection bus bar 42O1 and the V-phase output bus bar 42O2 and the connection portion between the W-phase parallel connection bus bar 43O1 and the W-phase output bus bar 43O2.

[0311] For example, the multiple switch modules 410 may be arranged in two rows in another axis direction (Y axis direction) perpendicular to the X axis direction, with two groups of switch modules 410 arranged in the X axis direction. The same may be true for the multiple switch modules 420 and the multiple switch modules 430. The connection between the U-phase parallel connection bus bar 41O1 and the U-phase output bus bar 41O2 may be located at a position farther away from the ends of the two groups farther away from the smoothing circuits 20 in the X axis direction, and at a substantially central position between the two groups in the Y axis direction. The same may be true for the connection between the V-phase parallel connection bus bar 42O1 and the V-phase output bus bar 42O2 and the connection between the W-phase parallel connection bus bar 43O1 and the W-phase output bus bar 43O2.

[0312] This makes it possible to make the lengths of the power paths between the junction of the DC input and the AC output in the inverter circuit 40 substantially equal.

[0313] In the present embodiment (fourth embodiment), the power conversion device 1 includes a smoothing circuit 20, an inverter circuit 40, and an output terminal 40T. Specifically, the inverter circuit 40 includes a U-phase circuit 41 configured by connecting a plurality of switch modules 410 in parallel, each of which has an upper and lower arm connected in series, each of which includes a plurality of semiconductor switches 410s, and connecting the connection points (AC output terminals 410O) of the upper and lower arms of each of the plurality of switch modules 410 to each other. Similarly, the inverter circuit 40 includes a V-phase circuit 42 configured by connecting a plurality of switch modules 420 in parallel, each of which has an upper and lower arm connected in series, each of which includes a plurality of semiconductor switches 420s, and connecting the connection points (AC output terminals 420O) of the upper and lower arms of each of the plurality of switch modules 420 to each other. Similarly, the inverter circuit 40 includes a W-phase circuit 43 configured by connecting a plurality of switch modules 430 in parallel, each of which has upper and lower arms connected in series, each of which includes a plurality of semiconductor switches 430s, and connecting the connection points (AC output terminals 430O) of the upper and lower arms of each of the plurality of switch modules 430 together. That is, the inverter circuit 40 includes a bridge circuit configured by connecting output circuits (U-phase circuit 41, V-phase circuit 42, and W-phase circuit 43) in parallel for a plurality of phases. The inverter circuit 40 outputs a predetermined AC power based on the DC power input from the smoothing circuit 20. The output terminal 40T outputs the predetermined AC power from the inverter circuit 40 to the outside. The inverter circuit 40 also includes a positive DC bus bar 40P that connects the positive terminals 410P, 420P, 430P of the multiple switch modules 410, 420, 430, and a negative DC bus bar 40N that connects the negative terminals 410N, 420N, 430N of the multiple switch modules 410, 420, 430. The inverter circuit 40 also includes a U-phase parallel connection bus bar 41O1 that connects the AC output terminals 410O of the multiple switch modules 410. The positive DC bus bar 40P, the negative DC bus bar 40N, and the U-phase parallel connection bus bar 41O1 have a laminate structure in which they are stacked with insulating layers 41I1, 41I2 interposed therebetween.Similarly, the inverter circuit 40 includes a V-phase parallel connection bus bar 42O1 that connects the AC output terminals 420O of the multiple switch modules 420 together. The positive DC bus bar 40P, the negative DC bus bar 40N, and the V-phase parallel connection bus bar 42O1 have a laminate structure in which they are stacked with insulating layers 42I1 and 42I2 interposed therebetween. Similarly, the inverter circuit 40 includes a W-phase parallel connection bus bar 43O1 that connects the AC output terminals 430O of the multiple switch modules 430 together. The positive DC bus bar 40P, the negative DC bus bar 40N, and the W-phase parallel connection bus bar 43O1 have a laminate structure in which they are stacked with insulating layers 43I1 and 43I2 interposed therebetween. A connection portion between the U-phase parallel connection busbar 41O1 and the wiring (U-phase output busbar 41O2) to the output terminal 40T (U-phase output terminal 41T) is provided at a position closer to the smoothing circuit 20 than the semiconductor switch 410s that is closest to the smoothing circuit 20 among all the arms (semiconductor switches 410s) included in the multiple switch modules 410. Similarly, a connection portion between the V-phase parallel connection busbar 42O1 and the wiring (V-phase output busbar 42O2) to the output terminal 40T (V-phase output terminal 42T) is provided at a position closer to the smoothing circuit 20 than the semiconductor switch 420s that is closest to the smoothing circuit 20 among all the arms (semiconductor switches 420s) included in the multiple switch modules 420. Similarly, the connection portion between the W-phase parallel connection bus bar 43O1 and the wiring (W-phase output bus bar 43O2) to the output terminal 40T (W-phase output terminal 43T) is provided at a position closer to the smoothing circuit 20 than the semiconductor switch 430s that is closest to the smoothing circuit 20 among all the arms (semiconductor switches 430s) included in the multiple switch modules 430.

[0314] As a result, the lamination structure of the busbars of the inverter circuit 40 can make the current density of all the power paths between the junction of the DC input and the AC input of the inverter circuit 40 approximately uniform. In addition, the arrangement of the connection between the U-phase parallel connection busbar 41O1 and the U-phase output busbar 41O2 can make the direction of the current in the U-phase positive side DC busbar 41P and the direction of the current in the U-phase parallel connection busbar 41O1 in real space opposite to each other. Similarly, the direction of the current in the U-phase parallel connection busbar 41O1 and the direction of the current in the U-phase negative side DC busbar 41N can be made opposite to each other. Therefore, the currents with approximately the same current density flow in opposite directions, so that the generated magnetic fields are offset, and the inductance of the U-phase positive side DC busbar 41P, the U-phase negative side DC busbar 41N, and the U-phase parallel connection busbar 41O1 can be reduced to a very small value. As a result, the difference in inductance of all the power paths between the junction of the DC input and the AC input passing through the multiple switch modules 410 becomes small, and the inductance between the power paths can be uniformed. Therefore, the power conversion device 1 can suppress and greatly reduce the difference in inductance of the loop of the power paths between the smoothing circuit 20 and the output terminal 40T (U-phase output terminal 41T) passing through each of the multiple switch modules 410. Therefore, the power conversion device 1 can suppress the imbalance of the current of the multiple semiconductor switches 410s (switch modules 410) and uniform the current. The same applies to the multiple switch modules 420. Therefore, the power conversion device 1 can suppress and greatly reduce the difference in inductance of the loop of the power paths between the smoothing circuit 20 and the output terminal 40T (V-phase output terminal 42T) passing through each of the multiple switch modules 420. Therefore, the power conversion device 1 can suppress the imbalance of the current of the multiple semiconductor switches 420s (switch modules 420) and uniform the current. The same applies to the multiple switch modules 430. Therefore, the power conversion device 1 can suppress and greatly reduce the difference in inductance of the loop power path between the smoothing circuit 20 and the output terminal 40T (W-phase output terminal 43T) that passes through each of the multiple switch modules 430.Therefore, the power conversion device 1 can suppress imbalance in the currents of the multiple semiconductor switches 430s (switch modules 430) and equalize the currents.

[0315] In this embodiment (fourth embodiment), the smoothing circuit 20 and the inverter circuit 40 may be arranged side by side in one axial direction (X-axis direction). A connection portion between the U-phase parallel connection bus bar 41O1 and the U-phase output bus bar 41O2 may be arranged in a position closer to the smoothing circuit 20 in the X-axis direction than a switch module 410 that is closest to the smoothing circuit 20 among the multiple switch modules 410. The same may be true for the connection portion between the V-phase parallel connection bus bar 42O1 and the V-phase output bus bar 42O2 and the connection portion between the W-phase parallel connection bus bar 43O1 and the W-phase output bus bar 43O2.

[0316] For example, the multiple switch modules 410 are arranged in two rows in another axial direction (Y-axis direction) perpendicular to the X-axis direction, in a top view, with two groups of switch modules 410 arranged in the X-axis direction. The same applies to the multiple switch modules 420 and the multiple switch modules 430. The connection between the U-phase parallel connection bus bar 41O1 and the wiring (U-phase output bus bar 41O2) to the U-phase output terminal 41T may be located closer to the smoothing circuit 20 than the ends of the two groups closer to the smoothing circuit 20 in the X-axis direction. The same applies to the connection between the V-phase parallel connection bus bar 42O1 and the wiring (V-phase output bus bar 42O2) to the V-phase output terminal 42T, and the connection between the W-phase parallel connection bus bar 43O1 and the wiring (W-phase output bus bar 43O2) to the W-phase output terminal 43T.

[0317] Specifically, the directions of current in the U-phase positive side DC busbar 41P and the U-phase parallel connection busbar 41O1, and the directions of current in the U-phase parallel connection busbar 41O1 and the U-phase negative side DC busbar 41N in the real space can be reversed. Similarly, the directions of current in the V-phase positive side DC busbar 42P and the V-phase parallel connection busbar 42O1, and the directions of current in the V-phase parallel connection busbar 42O1 and the V-phase negative side DC busbar 42N in the real space can be reversed. Similarly, the directions of current in the W-phase positive side DC busbar 43P and the W-phase parallel connection busbar 43O1, and the directions of current in the W-phase parallel connection busbar 43O1 and the W-phase negative side DC busbar 43N in the real space can be reversed.

[0318] Although the embodiments have been described in detail above, the present disclosure is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist described in the claims. [Explanation of symbols]

[0319] 1 Power conversion device 10 Rectifier circuit 20 Smoothing circuit 20I1, 20I2 Insulation layer 20N Negative busbar 20P positive bus bar 20PN Laminated Busbar 21 Smoothing capacitor 21P Positive terminal 21N Negative terminal 30. Fuse 40 Inverter circuit 40N negative DC busbar 40P positive DC busbar 40PN Laminated Busbar 40T output terminal 41 U phase circuit (output circuit) 41I1, 41I2 Insulating layer 41N U phase negative side DC bus bar 41O U-phase AC busbar 41O1 U-phase parallel connection bus bar 41O2 U-phase output bus bar 41P U phase positive side DC bus bar 41PN, 41PNO U-phase laminated bus bar 41T U phase output terminal 42 V phase circuit (output circuit) 42I1, 42I2 Insulating layer 42N V-phase negative side DC bus bar 42O V-phase AC busbar 42O1 V-phase parallel connection busbar 42O2 V-phase output bus bar 42P V phase positive side DC bus bar 42PN, 42PNO V-phase laminated busbar 42T V phase output terminal 43 W-phase circuit (output circuit) 43I1, 43I2 Insulating layer 43N W-phase negative side DC bus bar 43O W-phase AC busbar 43O1 W-phase parallel connection busbar 43O2 W-phase output bus bar 43P W phase positive side DC bus bar 43PN, 43PNO W-phase laminated busbar 43T W phase output terminal 410~416 Switch module (switch leg) 410N~416N Negative terminal 410O~416O AC output terminals (connection points) 410P~416P Positive terminal 410s, 411s1~416s1, 411s2~416s2 Semiconductor switches 411d1~416d1, 411d2~416d2 Freewheeling diodes 420~426 Switch module (switch leg) 420N~426N Negative terminal 420O~426O AC output terminals (connection points) 420P~426P Positive terminal 420s, 421s1~426s1, 421s2~426s2 Semiconductor switches 421d1~426d1,421d2~426d2 Freewheeling diodes 430~436 Switch module (switch leg) 430N~436N Negative terminal 430O~436O AC output terminals (connection points) 430P~436P Positive terminal 430s, 431s1~436s1, 431s2~436s2 Semiconductor switches 431d1~436d1, 431d2~436d2 Freewheeling diodes

Claims

1. A smoothing circuit; an inverter circuit including a bridge circuit in which a plurality of switch legs, each having upper and lower arms each including a plurality of semiconductor switches connected in series, are connected in parallel, and output circuits, each having connection points of the upper and lower arms of the plurality of switch legs connected to each other, are connected in parallel for a plurality of phases, and the inverter circuit outputs a predetermined AC power based on the DC power input from the smoothing circuit; an output terminal that outputs the predetermined AC power to an outside, the inverter circuit includes: a positive-side DC bus bar connecting positive terminals of the plurality of switch legs together; a negative-side DC bus bar connecting negative terminals of the plurality of switch legs together; and a parallel-connection bus bar connecting connection points of the upper and lower arms of each of the plurality of switch legs together; the positive DC bus bar and the negative DC bus bar have a laminate structure in which they are laminated with an insulating layer interposed therebetween, the parallel connection bus bar is configured such that individual paths between the smoothing circuit and a junction where all paths from each of the plurality of switch legs join, the individual paths passing through each of all the arms included in the plurality of switch legs, have approximately equal lengths and have approximately equal current densities throughout the entire paths. Power conversion equipment.

2. the parallel connection bus bar is configured so that current densities in portions of the individual paths having a common length are substantially equal to each other, and so that current densities in other portions are substantially equal to the current densities of the positive side DC bus bar and the negative side DC bus bar for each of the individual paths. The power conversion device according to claim 1 .

3. the smoothing circuit and the inverter circuit are arranged side by side in one axial direction, The switch legs are arranged side by side in the one axial direction, the parallel connection bus bar includes a plurality of legs provided to extend in an up-down direction from connection points of the upper and lower arms of each of the plurality of switch legs, the legs having substantially the same length and cross-sectional area, and a connecting portion connecting the plurality of legs to each other so as to extend in the one axial direction, the connecting portion is connected to a wiring leading to the output terminal at an end portion remote from the smoothing circuit in the one axial direction, and is configured such that a current density of each of the individual paths is substantially equal to a current density of the positive side DC bus bar and a current density of the negative side DC bus bar. The power conversion device according to claim 2 .

4. The switch legs are arranged in two groups in the one axial direction, and are arranged in two rows in another axial direction perpendicular to the one axial direction, The connecting portion connects the plurality of leg portions to each other so as to extend in the one axial direction and the other axial direction. The power conversion device according to claim 3 .

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