Power converter

Abstract

To provide a technique capable of restraining imbalance in current flowing through semiconductor switches 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. 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 nearer to the smoothing circuit 20 than a semiconductor switch 410s which is nearest to the smoothing circuit 20 among all arms (semiconductor switches 410s) included in the plurality of switch modules 410.SELECTED DRAWING: Figure 13

Description

Technical Field

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

Background Art

[0002] Conventionally, in a power conversion device in which a plurality of switch legs each composed of semiconductor switches corresponding to upper and lower arms are connected in parallel, a technique for equalizing the currents flowing through each semiconductor switch is known (see, for example, Patent Document 1).

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

[0004] Thereby, in Patent Document 1, the current flowing through the parallel connection bus bar (that is, the current merging from each switch leg or the current branching to each switch leg) and the current flowing through the output bus bar are in opposite directions to each other, and the magnetic fields generated by each can be canceled out. Therefore, the inductance of the power path in the width direction of the parallel connection bus bar when the currents of each switch leg merge or branch is reduced, and the imbalance of the currents flowing through each switch leg can be suppressed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] However, in Patent Document 1, the current in the output busbar corresponds to the sum of the currents in all switch legs, whereas the current flowing in the width direction at the other end of the parallel connection busbar is only the sum of the current that has passed through one switch leg or the currents in some of the switch legs. Therefore, the magnetic field generated by the output busbar may not be canceled out by the magnetic field generated by the parallel connection busbar and may remain. Consequently, this magnetic field may link with the current flowing in the width direction of the parallel connection busbar, causing inductance in the current path in the width direction of the parallel connection busbar, which may result in an imbalance in the current flowing through each switch leg.

[0007] Therefore, in view of the above issues, the objective is to provide a technology that can suppress the imbalance of current flowing through each semiconductor switch in a power conversion device in which multiple switch legs, each composed of semiconductor switches corresponding to the upper and lower arms, are connected in parallel. [Means for solving the problem]

[0008] To achieve the above objective, in one embodiment of this disclosure, Smoothing circuit and The device includes a bridge circuit comprising a bridge circuit in which multiple switch legs, each having upper and lower arms connected in series, are connected in parallel, and output circuits, each connecting the connection points of the upper and lower arms of the multiple switch legs, are connected in parallel for multiple phases, and an inverter circuit that outputs a predetermined AC power based on the DC power input from the smoothing circuit, It includes an output terminal that outputs the predetermined AC power to the outside, The inverter circuit includes a positive-side DC busbar that connects the positive terminals of a plurality of switch legs, a negative-side DC busbar that connects the negative terminals of a plurality of switch legs, and a parallel connection busbar that connects the connection points of the upper and lower arms of each of the plurality of switch legs. The positive electrode DC busbar, the negative electrode DC busbar, and the parallel connection busbar have a laminate structure in which they are stacked with an insulating layer in between. The smoothing circuit and the inverter circuit are arranged side by side in one axial direction. The multiple switch legs are arranged in two rows, each consisting of two groups aligned in the first axial direction, and the other axial direction perpendicular to the first axial direction. The connection between the parallel connection busbar and the wiring to the output terminal is, In the aforementioned axial direction, the two groups The smoothing circuit close stomach end It is provided in a position closer to the smoothing circuit. 、 The connection points of the upper and lower arms of the respective switch legs of the two groups are connected by a single parallel connecting busbar having a flat plate shape. ru, A power converter is provided. [Effects of the Invention]

[0009] According to the above-described embodiment, in a power conversion device in which a plurality of switch legs, each composed of semiconductor switches corresponding to the upper and lower arms, are connected in parallel, it is possible to provide a technology that can suppress the imbalance of the current flowing through each semiconductor switch. [Brief explanation of the drawing]

[0010] [Figure 1] This is a circuit diagram showing an example of a power conversion device according to the first embodiment. [Figure 2] This is a structural diagram showing an example of a power conversion device according to the first embodiment. [Figure 3] This is a structural diagram showing an example of a power conversion device according to the first embodiment. [Figure 4] This diagram illustrates an example of a busbar arrangement structure. [Figure 5] This diagram illustrates an example of a busbar arrangement structure. [Figure 6] This diagram illustrates an example of a busbar arrangement structure. [Figure 7] This is a circuit diagram showing an example of a power conversion device according to the second to fourth embodiments. [Figure 8] This is a structural diagram showing an example of a power conversion device according to the second embodiment. [Figure 9]It is a structural diagram showing an example of a power conversion device according to the second embodiment. [Figure 10] It is a diagram for explaining the current path flowing through each switch module. [Figure 11] It is a structural diagram showing an example of a power conversion device according to the third embodiment. [Figure 12] It is a structural diagram showing an example of a power conversion device according to the third embodiment. [Figure 13] It is a structural diagram showing an example of a power conversion device according to the fourth embodiment. [Figure 14] It is a structural diagram showing an example of a power conversion device according to the fourth embodiment.

Embodiments for Carrying out the Invention

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

[0012] [First Embodiment] First, the first embodiment will be described with reference to FIGS. 1 to 6.

[0013] [Overview 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 uses three-phase AC power input from a predetermined external power source (for example, a commercial power supply system) to generate predetermined three-phase AC power and supplies the generated three-phase AC power to a predetermined load device (for example, a 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 the three-phase AC power of the R phase, S phase, and T phase input from the external power source through the input terminal 11 and outputs predetermined DC power to the smoothing circuit 20.

[0017] The input terminal 11 includes an R-phase input terminal 111 into which R-phase power is input, an S-phase input terminal 112 into which S-phase power is input, and a T-phase input terminal 113 into which T-phase power is input.

[0018] As shown in Figure 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 configuration.

[0019] The smoothing circuit 20 smooths 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-side busbar 20P, a negative-side busbar 20N, and a smoothing capacitor 21.

[0021] The positive electrode busbar 20P is a flat plate-shaped component made of a material with relatively high conductivity (for example, copper or aluminum). The same applies to the negative electrode busbar 20N, U-phase positive electrode DC busbar 41P, U-phase negative electrode DC busbar 41N, V-phase positive electrode DC busbar 42P, V-phase negative electrode DC busbar 42N, W-phase positive electrode DC busbar 43P, and W-phase negative electrode DC busbar 43N, which will be described below.

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

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

[0024] The smoothing capacitor 21 is placed in parallel with the rectifier circuit 10 and the inverter circuit 40, in the power path connecting the positive busbar 20P and the negative busbar 20N. The smoothing capacitor 21 smooths the DC power output from the rectifier circuit 10 and the inverter circuit 40 by repeatedly charging and discharging as needed.

[0025] The smoothing capacitor 21 may be a single unit, or multiple smoothing capacitors 21 may be connected in parallel (see Figures 2 and 3).

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

[0027] The fuse 30 is positioned on the positive power path between the positive busbar 20P and the positive DC input terminal of the inverter circuit 40. The fuse 30 blows when an overcurrent occurs, protecting the power converter 1 (inverter circuit 40) from damage caused by overcurrent due to overload or short circuit.

[0028] The inverter circuit 40 generates three-phase AC power (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 U-phase AC power to the outside, a V-phase output terminal 42T that outputs V-phase AC power to the outside, and a W-phase output terminal 43T that outputs W-phase AC power to the outside.

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

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

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

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

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

[0034] The switch module 411 includes semiconductor switches 411s1 and 411s2 corresponding to the upper and lower arms, recirculation 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 the upper and lower arms, recirculation 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 the upper and lower arms, recirculation 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 the upper and lower arms, recirculation diodes 414d1 and 414d2, a positive terminal 414P, a negative terminal 414N, and an AC output terminal 414O.

[0038] In the following first embodiment, the semiconductor switches 411s1, 411s2, 412s1, 412s2, 413s1, 413s2, 414s1, and 414s2 may be collectively referred to as "semiconductor switch 410s," or any one of them may be referred to individually. Also 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 "positive terminal 410P." Also 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 "negative terminal 410N." Also 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 "AC output terminal 410O."

[0039] Since switch modules 411 to 414 have similar components and are composed of similar circuits, we will describe switch module 411 as a representative example and omit the descriptions of switch modules 412 to 414.

[0040] The semiconductor switches 411s1 and 411s2 (an example of upper and lower arms) are positioned in the power path connecting the positive terminal 411P and the negative terminal 411N, and are connected in series with 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 recirculating diodes 411d1 and 411d2 are connected in parallel to the semiconductor switches 411s1 and 411s2, respectively.

[0044] The positive terminal 411P is connected to the U-phase positive DC busbar 41P.

[0045] The negative terminal 411N is connected to the U-phase negative DC busbar 41N.

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

[0047] The U-phase AC busbar 41O connects the respective AC output terminals 411O to 414O of the switch modules 411 to 414 at one end, and connects to the U-phase output terminal 41T at the other end. As a result, the inverter circuit 40 can output the U-phase AC power output from the switch modules 411 to 414 to the outside from the U-phase output terminal 41T.

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

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

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

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

[0052] The switch module 421 includes semiconductor switches 421s1 and 421s2 corresponding to the upper and lower arms, recirculation 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 the upper and lower arms, recirculation 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 the upper and lower arms, recirculation 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 the upper and lower arms, recirculation diodes 424d1 and 424d2, a positive terminal 424P, a negative terminal 424N, and an AC output terminal 424O.

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

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

[0058] The semiconductor switches 421s1 and 421s2 (an example of upper and lower arms) are positioned in the power path connecting 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 recirculating diodes 421d1 and 421d2 are connected in parallel to the semiconductor switches 421s1 and 421s2, respectively.

[0062] The positive terminal 421P is connected to the V-phase positive DC busbar 42P.

[0063] The negative terminal 421N is connected to the V-phase negative DC busbar 42N.

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

[0065] The V-phase AC busbar 42O connects the respective AC output terminals 421O to 424O of the switch modules 421 to 424 at one end, and connects to the V-phase output terminal 42T at the other end. As a result, the inverter circuit 40 can output the V-phase AC power output from the switch modules 421 to 424 to the outside from the V-phase output terminal 42T.

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

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

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

[0069] Switch modules 431 to 434 are connected in parallel between the W-phase positive-side DC busbar 43P and the W-phase negative-side DC busbar 43N.

[0070] The switch module 431 includes semiconductor switches 431s1 and 431s2 corresponding to the upper and lower arms, recirculation 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 the upper and lower arms, recirculation 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 the upper and lower arms, recirculation 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 the upper and lower arms, recirculation diodes 434d1 and 434d2, a positive terminal 434P, a negative terminal 434N, and an AC output terminal 434O.

[0074] In the following first embodiment, the semiconductor switches 431s1, 431s2, 432s1, 432s2, 433s1, 433s2, 434s1, and 434s2 may be collectively referred to as "semiconductor switch 430s," or any one of them may be referred to individually. Also 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 "positive terminal 430P." Also 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 "negative terminal 430N." Also 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 "AC output terminal 430O."

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

[0076] The semiconductor switches 431s1 and 431s2 (an example of upper and lower arms) are positioned in the power path connecting 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 recirculating diodes 431d1 and 431d2 are connected in parallel to the semiconductor switches 431s1 and 431s2, respectively.

[0080] The positive terminal 431P is connected to the W-phase positive DC busbar 43P.

[0081] The negative terminal 431N is connected to the W-phase negative DC busbar 43N.

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

[0083] The W-phase AC busbar 43O connects the respective AC output terminals 431O to 434O of the switch modules 431 to 434 at one end, and is connected to the W-phase output terminal 43T at the other end. As a result, the inverter circuit 40 can output the W-phase AC power output from the switch modules 431 to 434 to the outside from the W-phase output terminal 43T.

[0084] <Structure of a power converter> Figures 2 and 3 are structural diagrams showing an example of a power converter 1 according to the first embodiment. Specifically, Figure 2 is a perspective view showing a state in which a part of the housing 1H of the power converter 1 has been removed, and Figure 3 is an exploded perspective view showing a state in which a part of the housing 1H of the power converter 1 has been removed and the output terminal 40T has been removed and moved upward. Figures 4 to 6 are diagrams illustrating an example of the busbar arrangement structure. Specifically, Figure 4 is an exploded perspective view schematically showing the components of the busbar disassembled, Figure 5 is a perspective view showing the completed state in which the components of the busbar in Figure 4 have been assembled, and Figure 6 is a side view schematically showing an example of the busbar arrangement structure.

[0085] In Figures 4 and 5, for convenience, the laminate busbar 20PN, U-phase laminate busbar 41PN, V-phase laminate busbar 42PN, and W-phase laminate busbar 43PN are depicted as a single integrated component. Also, in Figure 4, for convenience, the positive electrode busbar 20P of the smoothing circuit 20, and the U-phase positive electrode DC busbar 41P, V-phase positive electrode DC busbar 42P, and W-phase positive electrode DC busbar 43P of the inverter circuit 40 are depicted as a single integrated component. Similarly, in Figure 4, for convenience, the negative electrode busbar 20N of the smoothing circuit 20, and the U-phase negative electrode DC busbar 41N, V-phase negative electrode DC busbar 42N, and W-phase negative electrode DC busbar 43N of the inverter circuit 40 are depicted as a single integrated component. Similarly, in Figure 4, the insulating layers 20I1, 41I1, 42I1, and 43I1 are depicted as a single component. Similarly, in Figure 4, the insulating layers 20I2, 41I2, 42I2, and 43I2 are depicted as a single component. Also, in Figures 4 and 5, for simplicity, only a portion (4) of all the smoothing capacitors 21 in the smoothing circuit 20 are depicted as representative. Similarly, in Figures 4 and 5, for simplicity, only a portion (1) of all the switch modules 410 in the U-phase circuit 41 are depicted as representative. Similarly, in Figures 4 and 5, for simplicity, only a portion (1) of the switch modules 420 included in the V-phase circuit 42 are depicted as representative. Similarly, in Figures 4 and 5, for simplicity, only a portion (1) of the switch modules 430 included in the W-phase circuit 43 are depicted as representative. Furthermore, in Figure 6, for convenience, the depiction of insulating layers 20I1, 20I2, 41I1, 41I2, 42I1, 42I2, 43I1, and 43I2 has been omitted.

[0086] As shown in Figures 2 and 3, the power converter 1 has a roughly rectangular, box-shaped housing 1H in which various components are housed, in top view, side view, and front view. The term "roughly" is used to allow for manufacturing tolerances, etc., and will be used in the same sense hereafter.

[0087] Hereinafter, the longitudinal direction of the top view of the housing 1H will be referred to as the X-axis direction, the short direction of the top view of the housing 1H will be referred to as the Y-axis direction, and the vertical direction will be referred to as the Z-axis direction (see Figures 2 to 6).

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

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

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

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

[0092] The smoothing capacitor 21 has a substantially cylindrical shape and is mounted on the bottom surface of the housing 1H with its axial direction aligned with the vertical direction. A positive terminal 21P and a negative terminal 21N are provided on the end face (upper end face) opposite the mounting surface of the smoothing capacitor 21.

[0093] Specifically, as shown in Figures 2 and 3, the smoothing capacitors 21 are arranged in a row of four along the X-axis and in a row of six along the Y-axis.

[0094] On the upper surface of the smoothing capacitor 21, laminate busbars 20PN are arranged approximately parallel to the X-axis and Y-axis directions.

[0095] The laminate busbar 20PN has a roughly rectangular shape when viewed from above. The laminate busbar 20PN is arranged over an area that covers 24 smoothing capacitors 21 in the X-axis and Y-axis directions.

[0096] As shown in Figures 4 and 5, the laminated busbar 20PN is constructed by laminating the positive-side busbar 20P and the negative-side busbar 20N with an insulating layer 20I1 in between. Specifically, the laminated busbar 20PN has a four-layer laminate structure in which the negative-side busbar 20N is placed at the bottom, the insulating layer 20I1 is placed on top of it, the positive-side busbar 20P is placed on top of that, and the insulating layer 20I2 is placed at the top.

[0097] As shown in Figures 4 to 6, the bottommost negative-side busbar 20N is provided with a relatively small through-hole for bolting to the negative-side terminal 21N of the smoothing capacitor 21. This allows for direct connection between the negative-side terminal 21N of the smoothing capacitor 21 and the negative-side busbar 20N. In addition, the negative-side busbar 20N is provided with a relatively large through-hole to expose the positive-side terminal 21P in a top view. This allows for connection between the positive-side busbar 20P, which is located in a layer above the negative-side busbar 20N, and the positive-side terminal 21P.

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

[0099] As shown in Figures 4 to 6, the positive-side busbar 20P adjacent to the insulating layer 20I1 is provided with a relatively small through-hole for bolting to the positive-side terminal 21P of the smoothing capacitor 21. This allows the positive-side terminal 21P of the smoothing capacitor 21 and the positive-side busbar 20P to be directly connected. In addition, the positive-side busbar 20P is provided with a relatively large through-hole to expose the negative-side terminal 21N of the smoothing capacitor 21 (i.e., the through-hole for fastening the negative-side busbar 20N) in a top view. This allows the worker to access the fastening through-hole of the negative-side busbar 20N, which is located in a layer below the positive-side busbar 20P.

[0100] As shown in Figures 4 and 5, the uppermost insulating layer 20I2 is provided with relatively large through-holes that expose the positive terminal 21P (i.e., the through-hole for fastening the positive busbar 20P) and the negative terminal 21N (i.e., the through-hole for fastening the negative busbar 20N) of the smoothing capacitor 21 when viewed from above.

[0101] The positive-side busbar 20P and the negative-side busbar 20N of the laminated busbar 20PN have, for example, approximately the same thickness. This ensures that the current densities of the positive-side busbar 20P and the negative-side busbar 20N are approximately equal.

[0102] Furthermore, the laminated busbar 20PN may be arranged within the housing 1H such that the overlapping area of ​​the positive-side busbar 20P and the negative-side busbar 20N is relatively large (preferably maximized). Also, the thickness of the insulating layer 20I1 of the laminated busbar 20PN may be set so that the distance between the positive-side busbar 20P and the negative-side busbar 20N is relatively small while ensuring their insulation. This allows the current paths flowing in opposite directions to be brought closer together in space. As a result, at least a portion of the magnetic field generated by the current in the positive-side busbar 20P and the magnetic field generated by the current in the negative-side busbar 20N can be canceled out, and the inductance of the positive-side busbar 20P and the negative-side busbar 20N can be reduced. Furthermore, as described above, when the current densities are approximately equal, the magnitude of the magnetic field generated by both the current in the positive-side busbar 20P and the current in the negative-side busbar 20N becomes approximately equal, and most of the generated magnetic fields can be canceled out. Therefore, the inductance of the positive-side busbar 20P and the negative-side busbar 20N can be further suppressed. Consequently, the surge voltage of the power converter 1 can be suppressed by reducing the inductance of the positive-side busbar 20P and the negative-side busbar 20N.

[0103] As described above, the inverter circuit 40 includes a bridge circuit composed of a U-phase circuit 41, a V-phase circuit 42, and a 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 order along the Y-axis direction, from the end in the negative Y-axis direction to the end in the positive Y-axis direction.

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

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

[0107] As shown in Figures 4 and 5, the switch module 410 has a box shape, and fastening notches and bolt seating surfaces are provided at the corners when viewed from above.

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

[0109] Furthermore, the U-phase circuit 41 may be fitted with a switch leg of a different form than that of the switch module 410, in which a series connection of two semiconductor switches 410s is pre-housed within the enclosure. The same may apply to the switch module 420 of the V-phase circuit 42 and the switch module 430 of the W-phase circuit 43, and also to the second to fourth embodiments described later.

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

[0111] The U-phase laminate busbar 41PN is positioned over an area that covers four switch modules 410 in the X-axis and Y-axis directions.

[0112] As shown in Figures 4 and 5, the U-phase laminate busbar 41PN is constructed by laminating the U-phase positive electrode DC busbar 41P and the U-phase negative electrode DC busbar 41N with an insulating layer 41I1 in between. Specifically, the U-phase laminate busbar 41PN has a four-layer laminate structure in which the U-phase negative electrode DC busbar 41N is placed at the bottom, the insulating layer 41I1 is placed on top of that, the U-phase positive electrode DC busbar 41P is placed on top of that, and the insulating layer 41I2 is placed at the top.

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

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

[0115] The insulating layer 41I1 may be configured in a manner that is integrally connected with the insulating layers 42I1 and 43I1 described later (for example, as a single plate-shaped member). Similarly, the insulating layer 42I2 may be configured in a manner that is integrally connected with the insulating layers 42I2 and 43I2 described later (for example, as a single plate-shaped member). The same may apply to the second to fourth embodiments described later.

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

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

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

[0119] As shown in Figures 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 busbar 41P), the negative terminal 410N (i.e., the through-hole for fastening the U-phase negative DC busbar 41N), and the AC output terminal 410O of the switch module 410 to be exposed in a top view.

[0120] The U-phase positive electrode DC busbar 41P and the U-phase negative electrode DC busbar 41N of the U-phase laminated busbar 41PN have, for example, approximately the same thickness. This ensures that the current densities of the U-phase positive electrode DC busbar 41P and the U-phase negative electrode DC busbar 41N are approximately equal.

[0121] As shown in Figures 2 to 6, the U-phase AC busbar 41O connects the AC output terminal 410O and the U-phase output terminal 41T of the switch module 410. The U-phase AC busbar 41O includes a U-phase parallel connection busbar 41O1 and a U-phase output busbar 41O2.

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

[0123] As shown in Figures 2 and 3, the U-phase parallel connection busbar 41O1 is configured to be symmetrical with respect to a plane perpendicular to the X-axis at the central position between two switch modules 410 aligned in the X-axis direction. The U-phase parallel connection busbar 41O1 is also configured to be symmetrical with respect to a plane perpendicular to the Y-axis at the central position between two rows of switch modules 410 aligned in the Y-axis direction. The U-phase parallel connection busbar 41O1 is connected to the U-phase output busbar 41O2 at the portion corresponding to the central position of the AC output terminals 410O of the four switch modules 410 in both the X-axis and Y-axis directions. This makes the path lengths from each of the AC output terminals 410O of the four switch modules 410 to the U-phase output terminal 41T to be approximately equal. Furthermore, the current density of each path from each of the AC output terminals 410O of the four switch modules 410 to the U-phase output terminal 41T to be approximately equal. Therefore, the inductance of the power path between the four switch modules 410 and the U-phase output terminal 41T can be made approximately equal.

[0124] Specifically, the U-phase parallel connection busbar 41O1 includes two legs 41O1a and a connecting portion 41O1b.

[0125] The two legs 41O1a each have a flat plate shape that is substantially parallel to the X-axis and Z-axis directions. The two legs 41O1a each connect the AC output terminals 410O of two switch modules 410 that are arranged in two rows in the Y-axis direction and aligned in the X-axis direction. The two legs 41O1a are configured to be symmetrical with respect to a plane perpendicular to the X-axis direction at a substantially central position between the AC output terminals 410O of the two switch modules 410 that are aligned in the X-axis direction. Specifically, the leg 41O1a includes two seating surfaces, two lower legs, an intermediate leg, and an upper leg. The two seating surfaces have a substantially rectangular shape when viewed from above and are placed on each of the AC output terminals 410O of the two switch modules 410 that are aligned in the X-axis direction and have fastening holes for bolting to the AC output terminals 410O. The two lower legs are provided so as to extend upward from each of the two seating surfaces. The intermediate leg connects the two lower legs 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 intermediate leg and the center in the X-axis direction. As a result, the leg 41O1a can merge the paths from the respective AC output terminals 410O of the two switch modules 410 at approximately the same distance. In addition, the leg 41O1a can make the cross-sectional area of ​​the paths from the respective AC output terminals 410O of the two switch modules 410 approximately the same, and thus make the current density approximately the same. Furthermore, the two legs 41O1a are configured to be symmetrical with respect to a plane perpendicular to the Y-axis direction at approximately the center position of the AC output terminals 410O of the two switch modules 410 aligned in the Y-axis direction. As a result, the two legs 41O1a can make the paths from the two switch modules 410 to the merging point approximately the same distance.

[0126] The connecting portion 41O1b has a flat plate shape that is substantially parallel to the X-axis and Y-axis directions, and connects two leg portions 41O1a that are arranged side by side in the Y-axis direction. Specifically, the connecting portion 41O1b has a substantially rectangular shape when viewed from above, and connects the upper leg portions of the two leg portions 41O1a so as to extend in the Y-axis direction. Furthermore, the connecting portion 41O1b is configured symmetrically with respect to a plane perpendicular to the Y-axis at a substantially central position between the two leg portions 41O1a in the Y-axis direction, that is, at a substantially central position between the AC output terminals 410O of two (two rows) of switch modules 410 that are arranged in the Y-axis direction. In addition, the connecting portion 41O1b is connected to the U-phase output busbar 41O2 at a substantially central position between the two leg portions 41O1a in the Y-axis direction. As a result, the U-phase parallel connection busbar 41O1 can merge two paths from each of the four switch modules 410 at equal lengths, making all the paths approximately equal in length, and ensuring that the current density of each path is the same.

[0127] The U-phase output busbar 41O2 is provided so as to extend from the center of the Y-axis direction of the connecting portion 41O1b of the U-phase parallel connection busbar 41O1 toward the negative X-axis direction when viewed from above, 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 the same as that of the four switch modules 410 in the U-phase circuit 41, so the explanation is omitted.

[0130] As shown in Figures 4 and 5, the external shape of the switch module 420 is the same as that of the switch module 410.

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

[0132] At the upper end of the switch module 420, V-phase laminate busbars 42PN are arranged substantially parallel to each other in the X-axis and Y-axis directions.

[0133] The V-phase laminate busbar 42PN is positioned over an area that covers four switch modules 420 in the X-axis and Y-axis directions.

[0134] As shown in Figures 4 and 5, the V-phase laminate busbar 42PN is constructed by laminating the V-phase positive electrode DC busbar 42P and the V-phase negative electrode DC busbar 42N with an insulating layer 42I1 in between. Specifically, the V-phase laminate busbar 42PN has a four-layer laminate structure in which the V-phase negative electrode DC busbar 42N is placed at the bottom, the insulating layer 42I1 is placed on top of that, the V-phase positive electrode DC busbar 42P is placed on top of that, and the insulating layer 42I2 is placed at the top.

[0135] As described above, the V-phase positive electrode DC busbar 42P is configured to be integrally connected with the U-phase positive electrode DC busbar 41P and the W-phase positive electrode DC busbar 43P described later.

[0136] As described above, the V-phase negative electrode DC busbar 42N is configured to be integrally connected with the U-phase negative electrode DC busbar 41N and the W-phase negative electrode DC busbar 43N described later.

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

[0138] The detailed structure of the V-phase laminate busbar 42PN is the same as that of the U-phase laminate busbar 41PN, so its explanation is omitted.

[0139] As shown in Figures 2 to 6, the V-phase AC busbar 42O connects the AC output terminal 420O and the V-phase output terminal 42T of the switch module 420. The V-phase AC busbar 42O includes a V-phase parallel connection busbar 42O1 and a V-phase output busbar 42O2.

[0140] The arrangement and structure of the V-phase AC busbar 42O are the same as those of the U-phase AC busbar 41O, so the explanation is omitted.

[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 the same as that of the four switch modules 410 in the U-phase circuit 41, so the explanation is omitted.

[0143] As shown in Figures 4 and 5, the external shape of the switch module 430 is the same as that of the switch module 410.

[0144] The switch module 430 is positioned such that its longitudinal direction in a top view is approximately aligned with the X-axis direction. Along its longitudinal direction (i.e., the X-axis direction), the AC output terminal 430O, the negative terminal 430N, and the positive terminal 430P are arranged in order from the side closest to the smoothing circuit 20 (smoothing capacitor 21).

[0145] At the upper end of the switch module 430, W-phase laminate busbars 43PN are arranged substantially parallel to each other in the X-axis and Y-axis directions.

[0146] The W-phase laminate busbar 43PN is positioned over an area that covers four switch modules 430 in the X-axis and Y-axis directions.

[0147] As shown in Figures 4 and 5, the W-phase laminated busbar 43PN is constructed by laminating the W-phase positive electrode DC busbar 43P and the W-phase negative electrode DC busbar 43N with an insulating layer 43I1 in between. Specifically, the W-phase laminated busbar 43PN has a four-layer laminate structure in which the W-phase negative electrode DC busbar 43N is placed at the bottom, the insulating layer 43I1 is placed on top of that, the W-phase positive electrode DC busbar 43P is placed on top of that, and the insulating layer 43I2 is placed at the top.

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

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

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

[0151] The detailed structure of the W-phase laminate busbar 43PN is the same as that of the U-phase laminate busbar 41PN, so its explanation is omitted.

[0152] As shown in Figures 2 to 6, the W-phase AC busbar 43O connects the AC output terminal 430O and the W-phase output terminal 43T of the switch module 430. The W-phase AC busbar 43O includes a W-phase parallel connection busbar 43O1 and a W-phase output busbar 43O2.

[0153] The arrangement and structure of the W-phase AC busbar 43O are the same as those of the U-phase AC busbar 41O, so the explanation is omitted.

[0154] The laminated busbar 40PN may be arranged within the housing 1H such that the overlapping area of ​​the positive DC busbar 40P and the negative DC busbar 40N is relatively large (preferably maximized). Furthermore, the thickness of the insulating layers 41I1, 42I1, and 43I1 of the laminated busbar 40PN may be set such that the distance between the positive DC busbar 40P and the negative DC busbar 40N is relatively small while ensuring their insulation. This allows the current paths flowing in opposite directions to be brought closer together in space. Therefore, at least a portion of the magnetic field generated by the current in the positive DC busbar 40P and the magnetic field generated by the current in the negative DC busbar 40N can be canceled out. For example, when a U-phase current flows through the positive DC busbar 40P, a V-phase or W-phase current flows through the negative DC busbar 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 magnitude of the magnetic field generated by both the current in the positive-side DC busbar 40P and the current in the negative-side DC busbar 40N becomes approximately equal, and most of the generated magnetic field 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. Consequently, the surge voltage of the power converter 1 can be suppressed by reducing the inductance of the positive-side DC busbar 40P and the negative-side DC busbar 40N.

[0155] Thus, in the first embodiment, the positive-side busbar 20P and the negative-side busbar 20N of the smoothing circuit 20 have a laminated structure in which they are stacked via an insulating layer 20I1. Similarly, the positive-side DC busbar 40P and the negative-side DC busbar 40N of the inverter circuit 40 have a laminated structure in which they are stacked via insulating layers 41I1, 42I1, and 43I1. This reduces the inductance of the DC portion of the power path between the smoothing circuit 20 and the output terminal 40T, making it very small. As a result, surge voltages associated with the ON / OFF switching of the semiconductor switches 410s, 420s, and 430s of the power converter 1 can be suppressed.

[0156] Furthermore, in the first embodiment, the U-phase parallel connection busbar 41O1 is configured such that the length of the power path from each of the four switch modules 410's AC output terminals 410O to the U-phase output terminal 41T is approximately equal. Specifically, the U-phase parallel connection busbar 41O1 is configured such that the length of the power path between the four switch modules 410 (their AC output terminals 410O) and the connection point with the U-phase output busbar 41O2 is approximately equal. This makes it possible to relatively reduce the difference in inductance of each power path 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 power path in a complete circuit passing through the four switch modules 410 between the smoothing circuit 20 and the U-phase output terminal 41T. Furthermore, the U-phase parallel connection busbar 41O1 is configured such that the current density of each power path from each of the four switch modules 410's AC output terminals 410O to the U-phase output terminal 41T is approximately equal. This makes the inductance of each power path between the AC output terminals 410O and the U-phase output terminal 41T of the four switch modules 410 approximately equal. Therefore, the inductance of each power path in a complete circuit passing through the four switch modules 410 between the smoothing circuit 20 and the U-phase output terminal 41T can be made approximately equal. Similarly, the V-phase parallel connection busbar 42O1 is configured such that the lengths of the power paths from each of the four switch modules 420's AC output terminals 420O to the V-phase output terminal 42T are approximately equal. This makes the difference in inductance of each power path between the AC output terminals 420O and the V-phase output terminal 42T of the four switch modules 420 relatively small. Therefore, the difference in inductance between each of the power paths that pass through the four switch modules 420 between the smoothing circuit 20 and the V-phase output terminal 42T can be made relatively small. In addition, the V-phase parallel connection busbar 42O1 is configured such that the current density of each power path from each of the four switch modules 420 to the V-phase output terminal 42T is approximately equal.This makes the inductance of each power path between the AC output terminals 420O and the V-phase output terminals 42T of the four switch modules 420 approximately equal. Therefore, the inductance of each power path in a complete circuit through the four switch modules 420 between the smoothing circuit 20 and the V-phase output terminals 42T can be made approximately equal. Similarly, the busbar 43O1 for W-phase parallel connection is configured such that the lengths of the power paths from each of the four switch modules 430 to the W-phase output terminals 430 are approximately equal. This makes the difference in inductance of each power path between the AC output terminals 430O and the W-phase output terminals 43T of the four switch modules 430 relatively small. Therefore, the difference in inductance of each power path in a complete circuit through the four switch modules 430 between the smoothing circuit 20 and the W-phase output terminals 43T can be made relatively small. Furthermore, the busbar 43O1 for parallel connection of the W phase is configured such that the current density of each power path from each of the four switch modules 430's AC output terminals 430O to the W phase output terminal 43T is approximately equal. This makes the inductance of each power path between the AC output terminals 430O and the W phase output terminal 43T of the four switch modules 430 approximately equal. Therefore, the inductance of each power path in a complete circuit passing through the four switch modules 430 between the smoothing circuit 20 and the W phase output terminal 43T can be made approximately equal. As mentioned above, the inductance of the DC portion of the power path in a complete circuit between the smoothing circuit 20 and the output terminal 40T is very small, and the inductance of the AC portion is dominant. Thus, the current imbalance of the four switch modules 410, the four switch modules 420, and the four switch modules 430 can be suppressed, and the current can be made uniform.

[0157] In the first embodiment, the number of switch modules 410 connected in parallel can be arbitrary, as long as the length of the power path from the AC output terminal 410O of each switch module 410 to the U-phase output terminal 41T is approximately equal. That is, the number of switch modules 410 connected in parallel can be two, three, or five or more. For example, if the number of switch modules 410 connected in parallel is two, the U-phase parallel connection busbar 41O1 may consist only of legs 41O1a, and be connected to the U-phase output busbar 41O2 at approximately the center (midpoint) of the upper end of the legs 41O1a in the X-axis direction. The same applies to the number of switch modules 420 and switch modules 430. Furthermore, in the first embodiment, the multiple switch modules 410 may be arranged arbitrarily, as long as the length of the power paths from the AC output terminal 410O of each switch module 410 to the U-phase output terminal 41T is approximately equal. For example, the multiple switch modules 410 may be arranged in a row of three or more in the X-axis direction. Alternatively, for example, the multiple switch modules 410 may be arranged in a single row in the X-axis direction, or the row in the X-axis direction may be arranged in a row of three or more columns in the Y-axis direction. For example, the number of modules arranged in the X-axis direction and the Y-axis direction is preferably a power of 2. This makes it possible to make the length of all paths and the current density of each path approximately the same while merging two paths of equal length from the AC output terminal 410O of each of the multiple switch modules 410, as described above. The arrangement of switch modules 420 and 430 may also be similar. Furthermore, in the first embodiment, the configuration of the U-phase parallel connection busbar 41O1 can be arbitrary, as long as the length of the power path from the AC output terminal 410O of each switch module 410 to the U-phase output terminal 41T is approximately equal. For example, the U-phase parallel connection busbar 41O1 does not have to be the plane-symmetric configuration described above, as long as the length of the power path from the AC output terminal 410O of the four switch modules 410 to the U-phase output terminal 41T is approximately equal.Specifically, the two legs 41O1a of the U-phase parallel connection busbar 41O1 may not be symmetrical with respect to a plane perpendicular to the Y-axis direction, but rather may be configured with substantially identical shapes spaced apart in the Y-axis direction. The same may apply to the configurations of the V-phase parallel connection busbar 42O1 and the W-phase parallel connection busbar 43O1.

[0158] [Second Embodiment] Next, the second embodiment will be described with reference to Figures 7 to 10. The following description will focus on the differences from the power converter 1 according to the first embodiment, and explanations of the same or corresponding aspects as the first embodiment may be simplified or omitted.

[0159] <Overview of Power Converter> Figure 7 is a circuit diagram showing an example of a power converter 1 according to the second embodiment.

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

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

[0162] The U-phase circuit 41, as in the first embodiment, includes a U-phase positive-side DC busbar 41P, a U-phase negative-side DC busbar 41N, switch modules 411 to 414, and a U-phase AC busbar 41O. Furthermore, unlike the first embodiment, the U-phase circuit 41 also includes switch modules 415 and 416. In the second embodiment, and the third and fourth embodiments described later, switch modules 411 to 416 may be collectively referred to as "switch module 410," or any one of the switch modules 411 to 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] Switch modules 411 to 416 (an example of a switch leg) are connected in parallel between the U-phase positive-side DC busbar 41P and the U-phase negative-side DC busbar 41N.

[0164] The switch module 415 includes semiconductor switches 415s1 and 415s2 corresponding to the upper and lower arms, recirculation 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 the upper and lower arms, recirculation diodes 416d1 and 416d2, a positive terminal 416P, a negative terminal 416N, and an AC output terminal 416O.

[0166] 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 "semiconductor switch 410s," or any one of them may be referred to individually. Also in the second embodiment, and the third and fourth embodiments described later, the components corresponding to the positive terminals 411P to 416P of the above-mentioned "switch module 410" may be referred to as "positive terminal 410P." Also in the second embodiment, and the third and fourth embodiments described later, the components corresponding to the negative terminals 411N to 416N of the above-mentioned "switch module 410" may be referred to as "negative terminal 410N." Furthermore, in the second embodiment, and in the third and fourth embodiments described later, the components corresponding to the AC output terminals 411O to 416O of the "switch module 410" described above may be referred to as "AC output terminal 410O".

[0167] Switch modules 411 to 416 have similar components and are composed of similar circuits.

[0168] The U-phase AC busbar 41O connects the respective AC output terminals 411O to 416O of the switch modules 411 to 416 at one end, and connects to the U-phase output terminal 41T at the other end. As a result, the inverter circuit 40 can output the U-phase AC power output from the switch modules 411 to 416 to the outside from the U-phase output terminal 41T.

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

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

[0171] The switch module 425 includes semiconductor switches 425s1 and 425s2 corresponding to the upper and lower arms, recirculation 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 the upper and lower arms, recirculation diodes 426d1 and 426d2, a positive terminal 426P, a negative terminal 426N, and an AC output terminal 426O.

[0173] 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 "semiconductor switch 420s," or any one of them may be referred to individually. Also in the second embodiment, and the third and fourth embodiments described later, the components corresponding to the positive terminals 421P to 426P of the above-mentioned "switch module 420" may be referred to as "positive terminal 420P." Also in the second embodiment, and the third and fourth embodiments described later, the components corresponding to the negative terminals 421N to 426N of the above-mentioned "switch module 420" may be referred to as "negative terminal 420N." Furthermore, in the second embodiment, and in the third and fourth embodiments described later, the components corresponding to the AC output terminals 421O to 426O of the "switch module 420" described above may be referred to as "AC output terminal 420O".

[0174] Switch modules 421 to 426 have similar components and are composed of similar circuits.

[0175] The V-phase AC busbar 42O connects the respective AC output terminals 421O to 426O of the switch modules 421 to 426 at one end, and connects to the V-phase output terminal 42T at the other end. As a result, the inverter circuit 40 can output the V-phase AC power output from the switch modules 421 to 426 to the outside from the V-phase output terminal 42T.

[0176] The W-phase circuit 43, as in the first embodiment, includes a W-phase positive-side DC busbar 43P, a W-phase negative-side DC busbar 43N, switch modules 431 to 434, and a W-phase AC busbar 43O. Furthermore, unlike the first embodiment, the W-phase circuit 43 also includes switch modules 435 and 436. In the second embodiment, and the third and fourth embodiments described later, switch modules 431 to 436 may be collectively referred to as "switch module 430," or any one of the switch modules 431 to 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] Switch modules 431 to 436 are connected in parallel between the W-phase positive-side DC busbar 43P and the W-phase negative-side DC busbar 43N.

[0178] The switch module 435 includes semiconductor switches 435s1 and 435s2 corresponding to the upper and lower arms, recirculation 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 the upper and lower arms, recirculation diodes 436d1 and 436d2, a positive terminal 436P, a negative terminal 436N, and an AC output terminal 436O.

[0180] 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 "semiconductor switch 430s," or any one of them may be referred to individually. Also 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 "positive terminal 430P." Also 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 "negative terminal 430N." Furthermore, in the second embodiment, and in the third and fourth embodiments described later, the components corresponding to the AC output terminals 431O to 436O of the "switch module 430" described above may be referred to as "AC output terminal 430O".

[0181] Switch modules 431 to 436 have similar components and are composed of similar circuits.

[0182] The W-phase AC busbar 43O connects the respective AC output terminals 431O to 436O of the switch modules 431 to 436 at one end, and connects to the W-phase output terminal 43T at the other end. As a result, the inverter circuit 40 can output the W-phase AC power output from the switch modules 431 to 436 to the outside from the W-phase output terminal 43T.

[0183] <Structure of a power converter> Figures 8 and 9 are structural diagrams showing an example of a power converter according to the second embodiment. Specifically, Figure 8 is a perspective view showing a power converter 1 with a part of its housing 1H removed. Figure 9 is an exploded perspective view showing a power converter 1 with a part of its housing 1H removed, and with the output terminal 40T and the U-phase AC busbar 41O, V-phase AC busbar 42O, and W-phase AC busbar 43O removed and moved upward. Figure 10 is a diagram illustrating the current paths flowing through each switch module 410 arranged in a line along the X-axis. In Figure 10, the current paths passing through the three switch modules 410 arranged in a line along the X-axis are represented by white arrows, hatched arrows, and black arrows, 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, fuse 30, and inverter circuit 40 are arranged in order from one end to the other in the longitudinal direction inside the housing 1H (i.e., in the positive X-axis direction), similar to the first embodiment.

[0185] Furthermore, the output terminal 40T is located in the center of the longitudinal direction (X-axis direction) inside the housing 1H, and in the upper part of the housing 1H, similar to the first embodiment. Specifically, the output terminal 40T is located 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. 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 in the short direction to the center of the housing 1H (i.e., in the positive Y-axis direction), as in the first embodiment.

[0187] As described above, the inverter circuit 40 includes a bridge circuit composed of a U-phase circuit 41, a V-phase circuit 42, and a 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 order along the Y-axis direction, from the negative Y-axis end to the positive Y-axis end, similar to the first embodiment.

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

[0190] The six switch modules 410 are arranged in two groups of three, spaced equally apart in the X-axis direction, and in two rows in the Y-axis direction. Furthermore, as in the first embodiment, the six switch modules 410 are placed on top of another component mounted on the bottom surface of the housing 1H.

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

[0192] As shown in Figures 8 and 9, the U-phase laminate busbar 41PN is arranged at the upper end of the switch module 410 substantially parallel to the X-axis and Y-axis directions, similar to the case of the first embodiment.

[0193] The U-phase laminate busbar 41PN is positioned over an area that covers six switch modules 410 in the X-axis and Y-axis directions.

[0194] As shown in Figures 8 and 9, the U-phase AC busbar 41O connects the AC output terminal 410O and the U-phase output terminal 41T of the switch module 410. The U-phase AC busbar 41O includes a U-phase parallel connection busbar 41O1 and a U-phase output busbar 41O2, as in the first embodiment.

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

[0196] More specifically, the U-phase parallel connection busbar 41O1 includes six legs 41O1a and a connecting portion 41O1b.

[0197] Each of the six legs 41O1a has a flat plate shape that is substantially parallel to the X-axis and Z-axis directions. Each of the six legs 41O1a has a seating surface that rests on the AC output terminals 410O of the six switch modules 410, and a main leg that extends upward (in the positive Z-axis direction) from the seating surface. Furthermore, the dimensions of each of the six legs 41O1a in the Z-axis direction are set to be substantially the same. In addition, the cross-sectional area of ​​each of the six legs 41O1a is set to be substantially the same. This makes it possible to make the current density of each of the six legs 41O1a substantially equal.

[0198] The connecting portion 41O1b has a flat plate shape that is substantially parallel to the X-axis and Y-axis directions and connects the six leg portions 41O1a. Specifically, the connecting portion 41O1b has a substantially rectangular shape when viewed from above and is provided to extend in the X-axis and Y-axis directions over the area in which the six leg portions 41O1a are arranged. The end of the connecting portion 41O1b in the positive X-axis direction is provided at a position in the positive X-axis direction away from the AC output terminals 410O of the two switch modules 410 located at the positive X-axis ends of the six switch modules 410, and is connected to the U-phase output busbar 41O2.

[0199] As shown in Figure 10, the length of the current path flowing in the Z-axis direction from the DC input terminal of the U-phase circuit 41, through the three switch modules 410 aligned in the X-axis direction, to the connection point between the U-phase parallel connection busbar 41O1 and the U-phase output busbar 41O2, is all approximately equal. This is because, as mentioned above, the dimensions of the six legs 41O1a in the Z-axis direction are approximately the same. Furthermore, the length of the current path flowing in the X-axis direction from the DC input terminal of the U-phase circuit 41, through the three switch modules 410 aligned in the X-axis direction, to the connection point between the U-phase parallel connection busbar 41O1 and the U-phase output busbar 41O2, is also approximately equal. This is because the laminate busbar 20PN, the U-phase laminate busbar 41PN, and the connecting portion 41O1b are arranged approximately parallel to each other in the X-axis and Y-axis directions. Therefore, the total length of the current path from the DC input terminal of the U-phase circuit 41, through each of the three switch modules 410 aligned in the X-axis direction, to the connection point between the U-phase parallel connection busbar 41O1 and the U-phase output busbar 41O2, is approximately equal in all cases. The same can be said for the other row of three switch modules 410 aligned in the X-axis direction. Therefore, the total 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 approximately equal in all cases. Similarly, the total 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 approximately equal in all cases.

[0200] Furthermore, the cross-sectional area, i.e., width and thickness, of the connecting portion 41O1b is set so that the current density is approximately equal to that of the U-phase positive-side DC busbar 41P and the U-phase negative-side DC busbar 41N for each of the six power paths passing through each of the six switch modules 410. As a result, the length and current density of the 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 inductance of the power paths in a complete loop between the smoothing circuit 20 and the U-phase output terminal 41T passing through each of the six switch modules 410 can be made approximately equal and uniform.

[0201] As shown in Figures 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 that extends upward from the X-axis positive end of the connecting portion 41O1b of the U-phase parallel connection busbar 41O1, and a main portion that extends toward the U-phase output terminal 41T from the upper end of the folded portion in a manner substantially parallel to the X-axis and Y-axis directions.

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

[0203] The arrangement of the six switch modules 420 is the same as that of the six switch modules 410 in the U-phase circuit 41, so the explanation is omitted.

[0204] The switch module 420, like the switch module 410, is positioned so that its longitudinal direction in a top view is approximately aligned with the X-axis direction. Along its longitudinal direction (i.e., the X-axis direction), the AC output terminal 420O, the negative terminal 420N, and the positive terminal 420P are arranged in order from the side closest to the smoothing circuit 20 (smoothing capacitor 21).

[0205] At the upper end of the switch module 420, V-phase laminate busbars 42PN are arranged substantially parallel to each other in the X-axis and Y-axis directions.

[0206] The V-phase laminate busbar 42PN is positioned over an area that covers six switch modules 420 in the X-axis and Y-axis directions.

[0207] As shown in Figures 8 and 9, the V-phase AC busbar 42O connects the AC output terminal 420O and the V-phase output terminal 42T of the switch module 420. The V-phase AC busbar 42O includes a V-phase parallel connection busbar 42O1 and a V-phase output busbar 42O2.

[0208] The arrangement and structure of the V-phase AC busbar 42O are the same as those of the U-phase AC busbar 41O, so the explanation is omitted.

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

[0210] The arrangement of the six switch modules 430 is the same as that of the six switch modules 410 in the U-phase circuit 41, so the explanation is omitted.

[0211] The switch module 430 is positioned such that its longitudinal direction in a top view is approximately aligned with the X-axis direction. Along its longitudinal direction (i.e., the X-axis direction), the AC output terminal 430O, the negative terminal 430N, and the positive terminal 430P are arranged in order from the side closest to the smoothing circuit 20 (smoothing capacitor 21).

[0212] At the upper end of the switch module 430, W-phase laminate busbars 43PN are arranged substantially parallel to each other in the X-axis and Y-axis directions.

[0213] The W-phase laminate busbar 43PN is positioned over an area that covers six switch modules 430 in the X-axis and Y-axis directions.

[0214] The detailed structure of the W-phase laminate busbar 43PN is the same as that of the U-phase laminate busbar 41PN, so its explanation is omitted.

[0215] As shown in Figures 8 and 9, the W-phase AC busbar 43O connects the AC output terminal 430O and the W-phase output terminal 43T of the switch module 430. The W-phase AC busbar 43O includes a W-phase parallel connection busbar 43O1 and a W-phase output busbar 43O2.

[0216] The arrangement and structure of the W-phase AC busbar 43O are the same as those of the U-phase AC busbar 41O, so the explanation is omitted.

[0217] Thus, in the second embodiment, the U-phase parallel connection busbar 41O1 is configured such that the length of the power path between the DC input terminal of the U-phase laminate busbar 41PN and the connection point with the U-phase output busbar 41O2, passing through each of the six switch modules 410, is approximately equal. Furthermore, the U-phase parallel connection busbar 41O1 is configured such that the current density over the entire path of each power path between the DC input terminal of the U-phase laminate busbar 41PN and the connection point with the U-phase output busbar 41O2, passing through each of the six switch modules 410, is approximately equal. Specifically, the six legs 41O1a have approximately the same length and approximately the same cross-sectional area, and are configured so that their respective current densities are all approximately equal. Furthermore, the connecting portion 41O1b is configured such that the current density of each power path passing through each of the six switch modules 410 is approximately equal to the current density of the positive DC busbar 40P and the negative DC busbar 40N. In other words, the U-phase parallel connection busbar 41O1 is configured such that the current density of the portion where the lengths of each of the six power paths are common (i.e., the six legs 41O1a) is all approximately equal. The U-phase parallel connection busbar 41O1 is then configured such that the current density of the remaining portion, i.e., the portion corresponding to the difference in length of each power path (connecting portion 41O1b), is approximately equal to the current density of the positive DC busbar 40P and the negative DC busbar 40N for each of the six power paths. As a result, the length and current density of the complete power path 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 inductance of the power path between the smoothing circuit 20 and the U-phase output terminal 41T, passing through each of the six switch modules 410, can all be made approximately equal and uniform. Similarly, the V-phase parallel connection busbar 42O1 is configured such that the length of the power path between the DC input terminal of the V-phase laminate busbar 42PN and the connection point with the V-phase output busbar 42O2, passing through each of the six switch modules 420, is all approximately equal.Furthermore, the V-phase parallel connection busbar 42O1 is configured such that the current density across the entire power path between the DC input terminal of the V-phase laminate busbar 42PN and the connection point with the V-phase output busbar 42O2, passing through each of the six switch modules 420, is approximately equal. As a result, the inductance of all 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 busbar 43O1 is configured such that the length of all power paths between the DC input terminal of the W-phase laminate busbar 43PN and the connection point with the W-phase output busbar 43O2, passing through each of the six switch modules 430, is approximately equal. Furthermore, the W-phase parallel connection busbar 43O1 is configured such that the current density across the entire power path between the DC input terminal of the W-phase laminate busbar 43PN and the W-phase output busbar 43O2, passing through each of the six switch modules 430, is approximately equal. As a result, the inductance of the power path that completes a circuit between the smoothing circuit 20 and the W-phase output terminal 43T, passing through each of the six switch modules 430, can all be made approximately equal and uniform. Thus, current imbalances in the six switch modules 410, six switch modules 420, and six switch modules 430 can be suppressed, and current uniformity can be achieved.

[0218] In the second embodiment, the number of switch modules 410 connected in parallel may be arbitrary, as long as the length of the power path between the DC input terminal of the U-phase laminate busbar 41PN and the connection point of the U-phase output busbar 41O2, passing through each switch module 410, is approximately equal, and the current density over the entire path of 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 same may apply to the number of switch modules 420 and switch modules 430. Furthermore, in the second embodiment, the multiple switch modules 410 may be arranged arbitrarily, as long as the length of the power path between the DC input terminal of the U-phase laminate busbar 41PN and the connection point of the U-phase output busbar 41O2, passing through each switch module 410, is approximately equal, and the current density over the entire path of each path is configured to be equal. For example, multiple switch modules 410 may be arranged in a single row along the X-axis, or groups of a single row arranged along the X-axis may be arranged in three or more rows along the Y-axis. The arrangement of switch modules 420 and 430 may also be similar. Furthermore, in the second embodiment, the configuration of the U-phase parallel connection busbar 41O1 may be arbitrary, as long as the length of the power path between the DC input terminal of the U-phase laminate busbar 41PN and the connection portion with the U-phase output busbar 41O2, passing through each switch module 410, is approximately equal, and the current density over the entire path for each path is equal. For example, the U-phase parallel connection busbar 41O1 may be configured such that only the current density of each power path between the connection portion with the legs 41O1a at both ends in the X-axis direction at the connecting portion 41O1b is approximately equal to that of the U-phase positive-side DC busbar 41P and the U-phase negative-side DC busbar 41N. That is, the connecting portion 41O1b of the U-phase parallel connection busbar 41O1 may be configured such that the current density for each path section until all paths from each of the six switch modules 410 converge is approximately equal to that of the U-phase positive-side DC busbar 41P and the U-phase negative-side DC busbar 41N. The same configuration may also apply to the V-phase parallel connection busbar 42O1 and the W-phase parallel connection busbar 43O1.

[0219] [Third Embodiment] Next, the third embodiment will be described with reference to Figures 11 and 12. The circuit configuration of the power converter 1 according to the third embodiment is the same as that of the second embodiment (Figure 7) described above, so its explanation will be omitted. Hereafter, the explanation will focus on the parts that differ from the power converter 1 according to the first and second embodiments, and explanations of the same or corresponding parts as those of the first and second embodiments may be simplified or omitted.

[0220] <Structure of a power converter> Figures 11 and 12 are structural diagrams showing an example of a power converter 1 according to the third embodiment. Specifically, Figure 11 is a perspective view showing a power converter 1 with a part of its housing 1H removed. Figure 12 is an exploded perspective view showing a power converter 1 with a part of its housing 1H removed, and with the output terminal 40T and the U-phase output busbar 41O2, V-phase output busbar 42O2, and W-phase output busbar 43O2 removed and moved upward.

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

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

[0223] 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. 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 in the short direction to the center of the housing 1H (i.e., in the positive Y-axis direction), as in the first embodiment and the like.

[0224] As described above, the inverter circuit 40 includes a bridge circuit composed of a U-phase circuit 41, a V-phase circuit 42, and a 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 order along the Y-axis direction, from the end in the negative Y-axis direction to the end in the positive Y-axis direction, similar to the case of the first embodiment.

[0226] The U-phase circuit 41 includes six switch modules 410 (i.e., corresponding to the switch modules 411 to 416 described above), as in the second embodiment.

[0227] The six switch modules 410 are arranged in two groups of three, spaced equally apart in the X-axis direction, and in two rows in the Y-axis direction, similar to the second embodiment. Furthermore, the six switch modules 410 are placed on top of another component mounted on the bottom surface of the housing 1H, similar to the first embodiment.

[0228] The switch module 410 is arranged such that its longitudinal direction in a top view is approximately aligned with the X-axis direction, as in the first embodiment and the like. Along its longitudinal direction (i.e., the X-axis direction), the AC output terminal 410O, the negative terminal 410N, and the positive terminal 410P are arranged in order from the side closest to the smoothing circuit 20 (smoothing capacitor 21).

[0229] As shown in Figure 12, the U-phase laminate busbar 41PN is arranged at the upper end of the switch module 410 substantially parallel to the X-axis and Y-axis directions, similar to the case in the first embodiment.

[0230] The U-phase laminate busbar 41PN is positioned over an area that covers six switch modules 410 in the X-axis and Y-axis directions.

[0231] As shown in Figure 12, the U-phase AC busbar 41O connects the AC output terminal 410O and the U-phase output terminal 41T of the switch module 410. The U-phase AC busbar 41O includes a U-phase parallel connection busbar 41O1 and a U-phase output busbar 41O2, similar to the first embodiment.

[0232] The U-phase parallel connection busbar 41O1 has a flat plate shape that is substantially parallel in the X-axis and Y-axis directions, and in a top view, it has a substantially rectangular shape that covers an area that encompasses six switch modules 410. The U-phase parallel connection busbar 41O1 is further laminated on top of the uppermost insulating layer 41I2 (see Figure 4) of the U-phase laminate busbar 41PN. As a result, the U-phase negative electrode DC busbar 41N, the U-phase positive electrode DC busbar 41P, and the U-phase parallel connection busbar 41O1 constitute a laminated U-phase laminate busbar 41PNO, which is laminated from bottom to top via the insulating layers 41I1 and 41I2. Therefore, the current density of the U-phase parallel connection busbar 41O1 is substantially equal to that of the U-phase positive electrode DC busbar 41P and the U-phase negative electrode DC busbar 41N.

[0233] As shown in Figures 11 and 12, the U-phase parallel connection busbar 41O1 is provided with relatively large, roughly rectangular through-holes in a 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 busbar 41P), the negative terminal 410N (i.e., the through-hole for fastening the U-phase negative DC busbar 41N), and the AC output terminal 410O of the switch module 410 to be exposed in a top view. Therefore, workers 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 busbar 41O1.

[0234] As shown in Figures 11 and 12, 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 is connected to the X-axis positive end of the U-phase parallel connection busbar 41O1, that is, at a position further in the X-axis direction than the AC output terminal 410O of the switch module 410 at the X-axis positive end of the three switch modules 410 arranged in two rows in the X-axis direction. Furthermore, the U-phase output busbar 41O2 is connected to the X-axis positive end of the U-phase parallel connection busbar 41O1, and at approximately the center position in the Y-axis direction between the AC output terminals 410O of the group of three switch modules 410 arranged in two rows in the X-axis direction. As a result, the length of the power path between the DC input terminal of the U-phase circuit 41 and the connection points of the U-phase parallel connection busbar 41O1 and the U-phase output busbar 41O2, passing through each of the six switch modules 410, becomes approximately equal. Therefore, the length and current density of the complete power path between the smoothing circuit 20 and the U-phase output terminal 41T, passing through each of the six switch modules 410, become approximately equal. Thus, the inductance of the complete power path between the smoothing circuit 20 and the U-phase output terminal 41T, passing through the six switch modules 410, can be made approximately equal and uniform.

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

[0236] The arrangement of the six switch modules 420 is the same as that of the six switch modules 410 in the U-phase circuit 41, so the explanation is omitted.

[0237] The switch module 420, like the switch module 410, is positioned so that its longitudinal direction in a top view is approximately aligned with the X-axis direction. Along its longitudinal direction (i.e., the X-axis direction), the AC output terminal 420O, the negative terminal 420N, and the positive terminal 420P are arranged in order from the side closest to the smoothing circuit 20 (smoothing capacitor 21).

[0238] As shown in Figure 12, the V-phase laminate busbar 42PN is arranged at the upper end of the switch module 420 substantially parallel to the X-axis and Y-axis directions.

[0239] The V-phase laminate busbar 42PN is positioned over an area that covers six switch modules 420 in the X-axis and Y-axis directions.

[0240] As shown in Figure 12, the V-phase AC busbar 42O connects the AC output terminal 420O and the V-phase output terminal 42T of the switch module 420. The V-phase AC busbar 42O includes a V-phase parallel connection busbar 42O1 and a V-phase output busbar 42O2.

[0241] The V-phase parallel connection busbar 42O1 has a flat plate shape that is substantially parallel in the X-axis and Y-axis directions, and in a top view, it has a substantially rectangular shape that covers an area that encompasses six switch modules 420. The V-phase parallel connection busbar 42O1 is further laminated on top of the uppermost insulating layer 42I2 (see Figure 4) of the V-phase laminate busbar 42PN. As a result, the V-phase negative electrode DC busbar 42N, the V-phase positive electrode DC busbar 42P, and the V-phase parallel connection busbar 42O1 constitute a laminated V-phase laminate busbar 42PNO, which is laminated from bottom to top via 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 electrode DC busbar 42P and the V-phase negative electrode DC busbar 42N.

[0242] The arrangement and structure of the V-phase AC busbar 42O (busbar 42O1 for V-phase parallel connection and busbar 42O2 for V-phase output) are the same as those of the U-phase AC busbar 41O, so the explanation is omitted.

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

[0244] The arrangement of the six switch modules 430 is the same as that of the six switch modules 410 in the U-phase circuit 41, so the explanation is omitted.

[0245] Like the switch module 410, the switch module 430 is positioned so that its longitudinal direction in a top view is approximately aligned with the X-axis direction. Along its longitudinal direction (i.e., the X-axis direction), the AC output terminal 430O, the negative terminal 430N, and the positive terminal 430P are arranged in order from the side closest to the smoothing circuit 20 (smoothing capacitor 21).

[0246] As shown in Figure 12, the W-phase laminate busbar 43PN is arranged at the upper end of the switch module 430 substantially parallel to the X-axis and Y-axis directions.

[0247] The W-phase laminate busbar 43PN is positioned over an area that covers six switch modules 430 in the X-axis and Y-axis directions.

[0248] As shown in Figure 12, the W-phase AC busbar 43O connects the AC output terminal 430O and the W-phase output terminal 43T of the switch module 430. The W-phase AC busbar 43O includes a W-phase parallel connection busbar 43O1 and a W-phase output busbar 43O2.

[0249] The W-phase parallel connection busbar 43O1 has a flat plate shape that is substantially parallel in the X-axis and Y-axis directions, and in a top view, it has a substantially rectangular shape that covers an area that encompasses six switch modules 430. The W-phase parallel connection busbar 43O1 is further laminated on top of the uppermost insulating layer 43I2 (see Figure 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 laminated W-phase laminate busbar 43PNO, which is laminated from bottom to top via the insulating layers 43I1 and 43I2. Therefore, the current density of the W-phase parallel connection busbar 43O1 is substantially 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 busbar 43O (busbar 43O1 for W-phase parallel connection and busbar 43O2 for W-phase output) are the same as those of the U-phase AC busbar 41O, so the explanation is omitted.

[0251] Thus, in the third embodiment, the U-phase parallel connection busbar 41O1 has a laminate structure in which it is stacked with the U-phase positive-side DC busbar 41P and the U-phase negative-side DC busbar 41N via insulating layers 41I1 and 41I2. Furthermore, the U-phase parallel connection busbar 41O1 is connected to the U-phase output busbar 41O2 at a position further in the positive X-axis direction than the AC output terminal 410O of the switch module 410 at the end of the six switch modules 410 in the positive X-axis direction. As a result, the length and current density of the power path that completes a circuit 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 inductance of the power path that completes a circuit between the smoothing circuit 20 and the U-phase output terminal 41T passing through each of the six switch modules 410 can be made approximately equal and uniform. Similarly, the V-phase parallel connection busbar 42O1 has a laminate structure in which it is stacked with the V-phase positive-side DC busbar 42P and the V-phase negative-side DC busbar 42N via insulating layers 42I1 and 42I2. Furthermore, the V-phase parallel connection busbar 42O1 is connected to the V-phase output busbar 42O2 at a position further in the positive X-axis direction than the AC output terminal 420O of the switch module 420 at the end of the six switch modules 420 in the positive X-axis direction. As a result, the length and current density of the power path loop 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 inductance of the power path loop 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 busbar 43O1 has a laminate structure in which it is stacked with the W-phase positive-side DC busbar 43P and the W-phase negative-side DC busbar 43N via insulating layers 43I1 and 43I2. In addition, the W-phase parallel connection busbar 43O1 is connected to the W-phase output busbar 43O2 at a position further in the positive X-axis direction than the AC output terminal 430O of the switch module 430 at the end of the six switch modules 430 in the positive X-axis direction.As a result, the length and current density of the power path between the smoothing circuit 20 and the W-phase output terminal 43T passing through each of the six switch modules 430 become approximately equal. Therefore, the inductance of the power path between the smoothing circuit 20 and the W-phase output terminal 43T passing through each of the six switch modules 430 can be made approximately equal and uniform. Thus, current imbalances in the six switch modules 410, the six switch modules 420, and the six switch modules 430 can be suppressed and current uniformity can be achieved.

[0252] In the third embodiment, the number of switch modules 410 connected in parallel may be arbitrary, and may be two or more and five or less, or seven or more. The same may apply to the number of switch modules 420 and switch modules 430. Also, in the third embodiment, the arrangement of the multiple switch modules 410 may be arbitrary; for example, the multiple switch modules 410 may be arranged in a single row along the X-axis, or groups of one row arranged along the X-axis may be arranged in three or more rows along the Y-axis.

[0253] [Fourth Embodiment] Next, the fourth embodiment will be described with reference to Figures 13 and 14. The circuit configuration of the power converter 1 according to the fourth embodiment is the same as that of the second embodiment (Figure 7) described above, so its explanation will be omitted. Hereafter, the explanation will focus on the parts that differ from the power converter 1 according to the first to third embodiments, and explanations of the same or corresponding content as in the first to third embodiments may be simplified or omitted.

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

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

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

[0257] 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. 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 in the short direction to the center of the housing 1H (i.e., in the positive Y-axis direction), as in the first embodiment and the like.

[0258] As described above, the inverter circuit 40 includes a bridge circuit composed of a U-phase circuit 41, a V-phase circuit 42, and a 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 order along the Y-axis direction, from the end in the negative Y-axis direction to the end in the positive Y-axis direction, similar to the case of the first embodiment.

[0260] The U-phase circuit 41 includes six switch modules 410 (i.e., corresponding to the switch modules 411 to 416 described above), as in the case of the second embodiment, etc.

[0261] The six switch modules 410 are arranged in two groups of three, spaced equally apart in the X-axis direction, and in two rows in the Y-axis direction, similar to the second embodiment. Furthermore, the six switch modules 410 are placed on top of another component mounted on the bottom surface of the housing 1H, similar to the first embodiment.

[0262] The switch module 410 is arranged such that its longitudinal direction in a top view is approximately aligned with the X-axis direction, as in the first embodiment and the like. Along its longitudinal direction (i.e., the X-axis direction), the AC output terminal 410O, the negative terminal 410N, and the positive terminal 410P are arranged in order from the side closest to the smoothing circuit 20 (smoothing capacitor 21).

[0263] As shown in Figures 13 and 14, U-phase laminate busbars 41PN are arranged at the upper end of the switch module 410 substantially parallel to the X-axis and Y-axis directions, similar to the case in the first embodiment.

[0264] The U-phase laminate busbar 41PN is positioned over an area that covers six switch modules 410 in the X-axis and Y-axis directions.

[0265] As shown in Figures 13 and 14, the U-phase AC busbar 41O connects the AC output terminal 410O and the U-phase output terminal 41T of the switch module 410. The U-phase AC busbar 41O includes a U-phase parallel connection busbar 41O1 and a U-phase output busbar 41O2, similar to the first embodiment.

[0266] The U-phase parallel connection busbar 41O1, similar to the third embodiment, has a flat plate shape substantially parallel to the X-axis and Y-axis directions, and in a top view, has a substantially rectangular shape that covers an area encompassing six switch modules 410. The U-phase parallel connection busbar 41O1 is further laminated on top of the uppermost insulating layer 41I2 (see Figure 4) of the U-phase laminated busbar 41PN. As a result, the U-phase negative electrode side DC busbar 41N, the U-phase positive electrode side DC busbar 41P, and the U-phase parallel connection busbar 41O1 constitute a laminated U-phase laminated busbar 41PNO, which is laminated from bottom to top via the insulating layers 41I1 and 41I2. Therefore, the current density of the U-phase parallel connection busbar 41O1 is substantially equal to that of the U-phase positive electrode side DC busbar 41P and the U-phase negative electrode side DC busbar 41N.

[0267] As shown in Figures 13 and 14, 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 is connected to the negative X-axis end of the U-phase parallel connection busbar 41O1, that is, at a position further in the negative X-axis direction than the AC output terminal 410O of the switch module 410 at the negative X-axis end of the three switch modules 410 arranged in two rows along the X-axis. Furthermore, the U-phase output busbar 41O2 is connected to the negative X-axis end of the U-phase parallel connection busbar 41O1, and at approximately the center position in the Y-axis direction between the AC output terminals 410O of the group of three switch modules 410 arranged in two rows along the X-axis. As a result, the direction of the current flowing through the U-phase positive side DC busbar 41P toward each of the six switch modules 410 is in the positive X-axis direction. On the other hand, the direction of the current flowing from each of the six switch modules 410 toward the U-phase output terminal 41T through the U-phase parallel connection busbar 41O1 is in the opposite negative X-axis direction. Therefore, because currents of the same current density flow in opposite directions, the magnetic fields generated by the currents in the U-phase positive electrode DC busbar 41P and the U-phase parallel connection busbar 41O1 cancel each other out, and their inductance can be greatly reduced. Similarly, the direction of the current flowing from the U-phase output terminal 41T toward each of the six switch modules 410 through the U-phase parallel connection busbar 41O1 is in the positive X-axis direction. On the other hand, the direction of the current flowing from each of the six switch modules 410 toward the smoothing circuit 20 through the U-phase negative electrode DC busbar 41N is in the negative X-axis direction. Therefore, because currents of the same magnitude flow in opposite directions, the magnetic fields generated by the currents in the U-phase negative electrode DC busbar 41N and the U-phase parallel connection busbar 41O1 cancel each other out, and their inductance can be greatly reduced. As a result, the inductance of each component of the power path between the smoothing circuit 20 passing through the six switch modules 410 and the U-phase output terminal 41T becomes very small, thereby suppressing the difference in inductance between power paths and achieving inductance uniformity.

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

[0269] The arrangement of the six switch modules 420 is the same as that of the six switch modules 410 in the U-phase circuit 41, so the explanation is omitted.

[0270] The switch module 420, like the switch module 410, is positioned so that its longitudinal direction in a top view is approximately aligned with the X-axis direction. Along its longitudinal direction (i.e., the X-axis direction), the AC output terminal 420O, the negative terminal 420N, and the positive terminal 420P are arranged in order from the side closest to the smoothing circuit 20 (smoothing capacitor 21).

[0271] As shown in Figures 13 and 14, the V-phase laminate busbar 42PN is arranged at the upper end of the switch module 420 substantially parallel to the X-axis and Y-axis directions.

[0272] The V-phase laminate busbar 42PN is positioned over an area that covers six switch modules 420 in the X-axis and Y-axis directions.

[0273] As shown in Figures 13 and 14, the V-phase AC busbar 42O connects the AC output terminal 420O and the V-phase output terminal 42T of the switch module 420. The V-phase AC busbar 42O includes a V-phase parallel connection busbar 42O1 and a V-phase output busbar 42O2.

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

[0275] Since the arrangement and structure of the V-phase AC bus bar 42O (the bus bar 42O1 for V-phase parallel connection and the bus bar 42O2 for V-phase output) are the same as those of the U-phase AC bus bar 41O, the description thereof is omitted.

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

[0277] Since the arrangement structure of the six switch modules 430 is the same as that of the six switch modules 410 of the U-phase circuit 41, the description thereof is omitted.

[0278] The switch module 430 is arranged such that the longitudinal direction in a 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-side terminal 430N, and a positive-side terminal 430P are arranged side by side in order from the side closer to the smoothing circuit 20 (smoothing capacitor 21) along the longitudinal direction thereof (i.e., the X-axis direction).

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

[0280] The W-phase laminate busbar 43PN is positioned over an area that covers six switch modules 430 in the X-axis and Y-axis directions.

[0281] As shown in Figures 13 and 14, the W-phase AC busbar 43O connects the AC output terminal 430O and the W-phase output terminal 43T of the switch module 430. The W-phase AC busbar 43O includes a W-phase parallel connection busbar 43O1 and a W-phase output busbar 43O2.

[0282] The busbar 43O1 for W-phase parallel connection has a flat plate shape that is substantially parallel in the X-axis and Y-axis directions, similar to the third embodiment, and has a substantially rectangular shape that covers an area that encompasses six switch modules 430 when viewed from above. The busbar 43O1 for W-phase parallel connection is further laminated on top of the uppermost insulating layer 43I2 (see Figure 4) of the W-phase laminated busbar 43PN. As a result, the W-phase negative-side DC busbar 43N, the W-phase positive-side DC busbar 43P, and the busbar 43O1 for W-phase parallel connection constitute a laminated W-phase laminated busbar 43PNO, which is laminated from bottom to top via the insulating layers 43I1 and 43I2. Therefore, the current density of the busbar 43O1 for W-phase parallel connection is substantially equal to that of the W-phase positive-side DC busbar 43P and the W-phase negative-side DC busbar 43N.

[0283] The arrangement and structure of the W-phase AC busbar 43O (busbar 43O1 for W-phase parallel connection and busbar 43O2 for W-phase output) are the same as those of the U-phase AC busbar 41O, so the explanation is omitted.

[0284] Thus, in the fourth embodiment, the U-phase parallel connection busbar 41O1 has a laminate structure in which it is stacked with the U-phase positive electrode DC busbar 41P and the U-phase negative electrode DC busbar 41N via insulating layers 41I1 and 41I2. Furthermore, the U-phase parallel connection busbar 41O1 is connected to the U-phase output busbar 41O2 at a position further in the negative X-axis direction than the AC output terminal 410O of the switch module 410 at the end of the six switch modules 410 in the negative X-axis direction. As a result, the currents in the U-phase positive electrode DC busbar 41P and the U-phase parallel connection busbar 41O1 before and after passing through each of the six switch modules 410, as well as the currents in the U-phase parallel connection busbar 41O1 and the U-phase negative electrode DC busbar 41N, have the same current density and are in opposite directions in space. Therefore, the magnetic fields generated by the currents in the U-phase positive-side DC busbar 41P and the U-phase parallel connection busbar 41O1, as well as the currents in the U-phase parallel connection busbar 41O1 and the U-phase negative-side DC busbar 41N, cancel each other out, making the inductance of these power paths very small. As a result, differences in inductance between paths in the power path that passes through each of the six switch modules 410 between the smoothing circuit 20 and the U-phase output terminal 41T can be suppressed, and the inductance can be made uniform. Similarly, the V-phase parallel connection busbar 42O1 has a laminate structure in which it is stacked with the V-phase positive-side DC busbar 42P and the V-phase negative-side DC busbar 42N via insulating layers 42I1 and 42I2. Furthermore, the V-phase parallel connection busbar 42O1 is connected to the V-phase output busbar 42O2 at a position further in the negative X-axis direction than the AC output terminal 420O of the switch module 420 at the negative X-axis end of 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, as well as the currents in the V-phase parallel connection busbar 42O1 and the V-phase negative-side DC busbar 42N, as they pass through each of the six switch modules 420, have the same current density and are 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, as well as the currents in the V-phase parallel connection busbar 42O1 and the V-phase negative-side DC busbar 42N, cancel each other out, and the inductance of these power paths can be made very small.As a result, differences in inductance between power paths in a complete circuit 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 busbar 43O1 has a laminate structure in which it is stacked with the W-phase positive-side DC busbar 43P and the W-phase negative-side DC busbar 43N via insulating layers 43I1 and 43I2. In addition, the W-phase parallel connection busbar 43O1 is connected to the W-phase output busbar 43O2 at a position further in the negative X-axis direction than the AC output terminal 430O of the switch module 430 at the end of the six switch modules 430 in the negative X-axis direction. As a result, the currents in the W-phase positive-side DC busbar 43P and the W-phase parallel connection busbar 43O1, as well as the currents in the W-phase parallel connection busbar 43O1 and the W-phase negative-side DC busbar 43N, passing through each of the six switch modules 430, have the same current density and are in opposite directions in space. Therefore, the magnetic fields generated by the currents in the W-phase positive-side DC busbar 43P and the W-phase parallel connection busbar 43O1, as well as the currents in the W-phase parallel connection busbar 43O1 and the W-phase negative-side DC busbar 43N, cancel each other out, making the inductance of these power paths very small. Consequently, the difference in inductance between paths in the power path that passes through each of the six switch modules 430 between the smoothing circuit 20 and the W-phase output terminal 43T is suppressed, and the inductance can be made uniform. Therefore, it is possible to suppress the current imbalance in each of the six switch modules 410, six switch modules 420, and six switch modules 430, and to equalize the current.

[0285] In the fourth embodiment, the number of switch modules 410 connected in parallel may be arbitrary, and may be two or more and five or less, or seven or more. The same applies to the number of switch modules 420 and switch modules 430. In the fourth embodiment, the arrangement of the multiple switch modules 410 may be arbitrary; for example, the multiple switch modules 410 may be arranged in a single row along the X-axis, or groups of one row arranged along the X-axis may be arranged in three or more rows along the Y-axis.

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

[0287] In this embodiment (first embodiment), the power converter 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, which is formed by connecting multiple switch modules 410, each having upper and lower arms connected in series, and connecting the connection points (AC output terminals 410O) of the upper and lower arms of each of the multiple switch modules 410 to each other. Similarly, the inverter circuit 40 includes a V-phase circuit 42, which is formed by connecting multiple switch modules 420, each having upper and lower arms connected in series, and connecting the connection points (AC output terminals 420O) of the upper and lower arms of each of the multiple switch modules 420 to each other. Similarly, the inverter circuit 40 includes a W-phase circuit 43, which is formed by connecting multiple switch modules 430 in parallel, each containing multiple semiconductor switches 430s with upper and lower arms connected in series, and by connecting the connection points (AC output terminals 430O) of the upper and lower arms of each of the multiple switch modules 430. That is, the inverter circuit 40 includes a bridge circuit formed by connecting multiple output circuits (U-phase circuit 41, V-phase circuit 42, and W-phase circuit 43) in parallel for multiple phases. The inverter circuit 40 then 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. Furthermore, the inverter circuit 40 includes a positive-side DC busbar 40P that connects the positive terminals 410P, 420P, and 430P of multiple switch modules 410, 420, and 430 to each other, and a negative-side DC busbar 40N that connects the negative terminals 410N, 420N, and 430N of multiple switch modules 410, 420, and 430 to each other. In addition, the inverter circuit 40 includes a U-phase parallel connection busbar 41O1 that connects the AC output terminals 410O of multiple switch modules 410 to each other. Similarly, the inverter circuit 40 includes a V-phase parallel connection busbar 42O1 that connects the AC output terminals 420O of multiple switch modules 420 to each other. Similarly, the inverter circuit 40 includes a W-phase parallel connection busbar 43O1 that connects the AC output terminals 430O of multiple switch modules 430 to each other.Furthermore, the positive-side DC busbar 40P and the negative-side DC busbar 40N have a laminate structure in which they are stacked via insulating layers 41I1, 42I1, and 43I1. The U-phase parallel connection busbar 41O1 is configured such 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 converge are approximately equal. Similarly, the V-phase parallel connection busbar 42O1 is configured such 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 converge are approximately equal. Similarly, the W-phase parallel connection busbar 43O1 is configured such 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 converge are approximately equal.

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

[0289] In this case, if the inductance differs for each path through multiple switch legs, an imbalance will occur in the current passing through the multiple switch legs, potentially causing current to concentrate in the semiconductor switches within some of the switch legs. As a result, the semiconductor switch elements may be damaged due to the temperature rise caused by the losses.

[0290] On the other hand, it is also possible to determine the current capacity of the power converter by matching it to the allowable current of the semiconductor switch where the current is most concentrated, thereby taking into account the current imbalance. However, in this case, only a relatively lower current than the allowable current will flow through semiconductor switches other than the one 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 set of switch legs cannot be effectively used, and the current capacity of the power converter may not be increased significantly.

[0291] In contrast, in this embodiment (first embodiment), the laminate structure of the positive-side DC busbar 40P and the negative-side DC busbar 40N makes it possible to significantly reduce the inductance of the DC wiring portions on the positive and negative sides of the inverter circuit 40. As a result, the inductance of the AC wiring portion becomes dominant in the inductance of the power path that completes a loop between the smoothing circuit 20 and the output terminal 40T. Furthermore, by configuring the paths from all the arms (semiconductor switches 410s) included in the multiple switch modules 410 to the junction to be approximately equal in length, the difference in inductance of the power paths passing through each semiconductor switch 410s in the U-phase parallel connection busbar 410O1 can be relatively reduced. As a result, the power converter 1 can relatively reduce the difference in inductance of the power path that completes a loop between the smoothing circuit 20 and the output terminal 40T (U-phase output terminal 41T) for each of the multiple switch modules 410. Therefore, the power converter 1 can suppress the current imbalance in the multiple semiconductor switches 410s (switch modules 410) and equalize the current. The same applies to the multiple switch modules 420. As a result, the power converter 1 can relatively reduce the difference in inductance of the power path that goes through each of the multiple switch modules 420, specifically between the smoothing circuit 20 and the output terminal 40T (V-phase output terminal 42T). Therefore, the power converter 1 can suppress the current imbalance in the multiple semiconductor switches 420s (switch modules 420) and equalize the current. The same applies to the multiple switch modules 430. As a result, the power converter 1 can relatively reduce the difference in inductance of the power path that goes through each of the multiple switch modules 430, specifically between the smoothing circuit 20 and the output terminal 40T (W-phase output terminal 43T). Therefore, the power converter 1 can suppress the current imbalance in the multiple semiconductor switches 430s (switch module 430) and equalize the current.

[0292] Furthermore, in this embodiment (first embodiment), the U-phase parallel connection busbar 41O1 is configured such that the current density for each path between all semiconductor switches 410s included in the plurality of switch modules 410 and the confluence point where all paths from each of the plurality of switch modules 410 converge is approximately equal. The same may apply to the V-phase parallel connection busbar 42O1 and the W-phase parallel connection busbar 43O1.

[0293] This makes it possible to make the inductance of the power path passing through each semiconductor switch 410s in the U-phase parallel connection busbar 41O1 approximately equal. Therefore, the power converter 1 can make the inductance of the power path that passes through each of the multiple switch modules 410 approximately equal for one loop between the smoothing circuit 20 and the output terminal 40T (U-phase output terminal 41T). Thus, the power converter 1 can further suppress the current imbalance in the multiple semiconductor switches 410s (switch modules 410) and further equalize the current. The same effect is also achieved with the V-phase parallel connection busbar 42O1 and the W-phase parallel connection busbar 43O1.

[0294] Furthermore, in this embodiment (first embodiment), two switch modules 410 included in the plurality of switch modules 410 are arranged side by side in one axial direction (X-axis direction). The same may apply to the plurality of switch modules 420 and the plurality of switch modules 430. The busbar 41O1 for U-phase parallel connection may have the paths from the two switch modules 410 to the U-phase output terminal 41T merge at approximately the midpoint between the AC output terminals 410O of the two switch modules 410 in the X-axis direction. The same may apply to the busbar 42O1 for V-phase parallel connection and the busbar 43O1 for W-phase parallel connection.

[0295] As a result, for the bus bar 41O1 for U-phase parallel connection, for each combination of two switch modules 410, the paths from the AC output terminals 410O of the two switch modules 410 can be merged so that their lengths are substantially the same. The same operation and effect also apply to the bus bar 42O1 for V-phase parallel connection and the bus bar 43O1 for W-phase parallel connection.

[0296] Also, in this embodiment (the first embodiment), the plurality of switch modules 410 connected in parallel may include a plurality of combinations of two switch modules 410. The same may apply to the plurality of switch modules 420 connected in parallel and the plurality of switch modules 430 connected in parallel. And the bus bar 41O1 for U-phase parallel connection may be configured such that the lengths of the respective power paths between the intermediate merging portion where the paths from each of the two switch modules 410 for each combination merge and the merging portion where the paths from each of all the switch modules 410 merge are substantially equal. The same may apply to the bus bar 42O1 for V-phase parallel connection and the bus bar 43O1 for W-phase parallel connection.

[0297] As a result, in the bus bar 41O1 for U-phase parallel connection, the lengths of the paths until all the paths from each of the plurality of switch modules 410 connected in parallel merge can be made substantially equal. The same operation and effect also apply to the bus bar 42O1 for V-phase parallel connection and the bus bar 43O1 for W-phase parallel connection.

[0298] Furthermore, in this embodiment (first embodiment), the multiple (4) switch modules 410 connected in parallel may be arranged in two rows in the other axis direction (Y axis direction) perpendicular to the X axis direction, with two sets of two switch modules 410 aligned in the X axis direction. The same may apply to multiple (4) switch modules 420 and multiple (4) switch modules 430. The U-phase parallel connection busbar 41O1 is configured to be substantially symmetrical in the X axis direction with respect to the vertical plane at the central position of the two switch modules 410. The U-phase parallel connection busbar 41O1 may also be configured to be substantially symmetrical in the Y axis direction with respect to the vertical plane at the central position of the two sets. The connection portion of the U-phase parallel connection busbar 41O1 to the wiring up to the U-phase output terminal 41T (U-phase output busbar 41O2) may be configured to be at the central 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 apply to the V-phase parallel connection busbar 42O1 and the W-phase parallel connection busbar 43O1.

[0299] This allows the U-phase parallel connection busbar 41O1 to make the length of each path of the multiple (four) parallel-connected switch modules 410 approximately equal until they merge. Therefore, the power converter 1 can make the inductance of the paths passing through each semiconductor switch 410s approximately equal. The same effect and benefits are also achieved with the V-phase parallel connection busbar 42O1 and the W-phase parallel connection busbar 43O1.

[0300] Furthermore, in this embodiment (second embodiment), the power converter 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, which is formed by connecting multiple switch modules 410, each having upper and lower arms connected in series, and connecting the connection points (AC output terminals 410O) of the upper and lower arms of each of the multiple switch modules 410 to each other. Similarly, the inverter circuit 40 includes a V-phase circuit 42, which is formed by connecting multiple switch modules 420, each having upper and lower arms connected in series, and connecting the connection points (AC output terminals 420O) of the upper and lower arms of each of the multiple switch modules 420 to each other. Similarly, the inverter circuit 40 includes a W-phase circuit 43, which is formed by connecting multiple switch modules 430 in parallel, each containing multiple semiconductor switches 430s with upper and lower arms connected in series, and by connecting the connection points (AC output terminals 430O) of the upper and lower arms of each of the multiple switch modules 430. That is, the inverter circuit 40 includes a bridge circuit formed by connecting multiple output circuits (U-phase circuit 41, V-phase circuit 42, and W-phase circuit 43) in parallel for multiple phases. The inverter circuit 40 then 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. Furthermore, the inverter circuit 40 includes a positive-side DC busbar 40P that connects the positive terminals 410P, 420P, and 430P of multiple switch modules 410, 420, and 430 to each other, and a negative-side DC busbar 40N that connects the negative terminals 410N, 420N, and 430N of multiple switch modules 410, 420, and 430 to each other. In addition, the inverter circuit 40 includes a U-phase parallel connection busbar 41O1 that connects the AC output terminals 410O of multiple switch modules 410 to each other. Similarly, the inverter circuit 40 includes a V-phase parallel connection busbar 42O1 that connects the AC output terminals 420O of multiple switch modules 420 to each other.Similarly, the inverter circuit 40 includes a W-phase parallel connection busbar 43O1 that connects the AC output terminals 430O of multiple switch modules 430. The positive-side DC busbar 40P and the negative-side DC busbar 40N have a laminate structure in which they are stacked via insulating layers 41I1, 42I1, and 43I1. The U-phase parallel connection busbar 41O1 is configured such that the lengths of the power paths between the smoothing circuit 20 and the confluence point where the paths from each of the multiple switch modules 410 converge, passing through each of the arms (semiconductor switches 410s) included in the multiple switch modules 410, are approximately equal. The U-phase parallel connection busbar 41O1 is configured such that the current density across the entire path of each power path between the smoothing circuit 20 and the confluence point, passing through each of the arms included in the multiple switch modules 410, is approximately equal. Similarly, the V-phase parallel connection busbar 42O1 is configured such that the lengths of each power path between the smoothing circuit 20 and the confluence point where the paths from each of the multiple switch modules 420 converge, passing through each of the arms (semiconductor switches 420s) included in the multiple switch modules 420, are approximately equal. Furthermore, the V-phase parallel connection busbar 42O1 is configured such that the current density across the entire path of each power path between the smoothing circuit 20 and the confluence point, passing through each of the arms included in the multiple switch modules 420, is approximately equal. Similarly, the W-phase parallel connection busbar 43O1 is configured such that the lengths of each power path to the confluence point where the paths from the smoothing circuit 20 and each of the multiple switch modules 430 converge, passing through each of the arms (semiconductor switches 430s) included in the multiple switch modules 430, are approximately equal. The busbar 43O1 for W-phase parallel connection is configured such that the current density across the entire power path between the smoothing circuit 20 and the junction, passing through each of the arms included in the multiple switch modules 430, is approximately equal.

[0301] As a result, in the inverter circuit 40, the length of all paths between the DC input and AC output junction, and the current density throughout each path, can be made uniform. Therefore, the power converter 1 can make the inductance of the complete power path between the smoothing circuit 20 and the output terminal 40T (U-phase output terminal 41T) approximately equal for each of the power paths passing through the multiple switch modules 410. Thus, the power converter 1 can suppress current imbalance in the multiple semiconductor switches 410s (switch modules 410) and achieve current uniformity. The same applies to the multiple switch modules 420. Therefore, the power converter 1 can make the inductance of the complete power path between the smoothing circuit 20 and the output terminal 40T (V-phase output terminal 42T) approximately equal for each of the power paths passing through the multiple switch modules 420. Thus, the power converter 1 can suppress current imbalance in the multiple semiconductor switches 420s (switch modules 420) and achieve current uniformity. The same applies to the multiple switch modules 430. Therefore, the power converter 1 can make the inductance of the power path between the smoothing circuit 20 and the output terminal 40T (W-phase output terminal 43T) approximately equal for each of the power paths passing through the multiple switch modules 430. Thus, the power converter 1 can suppress the current imbalance of each of the multiple semiconductor switches 430s (switch modules 430) and equalize the current.

[0302] Furthermore, in this embodiment (second embodiment), the U-phase parallel connection busbar 41O1 may be configured such that the current density in the portion where the length of each power path passing through each of the multiple switch modules 410 is common is approximately equal. The U-phase parallel connection busbar 41O1 may then be configured such that the current density in the remaining portion, i.e., the portion corresponding to the difference in the length of each power path, is approximately equal to the current density of the positive-side DC busbar 40P and the negative-side DC busbar 40N for each power path. The same may apply to the V-phase parallel connection busbar 42O1 and the W-phase parallel connection busbar 43O1.

[0303] As a result, in the inverter circuit 40, DC input and AC Out The current density across the entire path for each path between the convergence point and the other path can be made approximately equal.

[0304] Furthermore, in this 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). Also, the multiple switch modules 410 may be arranged side by side in the X-axis direction. The same may apply to the multiple switch modules 420 and the multiple switch modules 430. The U-phase parallel connection busbar 41O1 is provided so as to extend in the vertical direction (Z-axis direction) from the connection point (AC output terminal 410O) of the upper and lower arms of each of the multiple switch modules 410, and may include a plurality of legs 41O1a having substantially the same length and substantially the same cross-sectional area. The U-phase parallel connection busbar 41O1 may also include a connecting portion 41O1b that connects the plurality of legs 41O1a so as to extend in the X-axis direction. Furthermore, the connecting portion 41O1b may be connected to the wiring (U-phase output busbar 41O2) up to the output terminal 40T (U-phase output terminal 41T) at the end furthest from the smoothing circuit 20 in the X-axis direction. The connecting portion 41O1b may be configured such 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 busbar 40P and the negative-side DC busbar 40N. The same may apply to the V-phase parallel connection busbar 42O1 and the W-phase parallel connection busbar 43O1.

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

[0306] Furthermore, in this embodiment (second embodiment), the multiple switch modules 410 may be arranged in two groups, one in an axial direction (X-axis direction), and the other in an axial direction (Y-axis direction) perpendicular to the X-axis direction. The connecting portion 41O1b of the U-phase parallel connection busbar 41O1 may connect multiple legs 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 length of all power paths between the DC input and the AC output junction and the current density across the entire path of each power path approximately equal in the inverter circuit 40.

[0308] Furthermore, in this embodiment (third embodiment), the power converter 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, which is formed by connecting multiple switch modules 410, each having upper and lower arms containing multiple semiconductor switches 410s connected in series, in parallel, and connecting the connection points (AC output terminals 410O) of the upper and lower arms of each of the multiple switch modules 410 to each other. Similarly, the inverter circuit 40 includes a V-phase circuit 42, which is formed by connecting multiple switch modules 420, each having upper and lower arms containing multiple semiconductor switches 420s connected in series, in parallel, and connecting the connection points (AC output terminals 420O) of the upper and lower arms of each of the multiple switch modules 420 to each other. Similarly, the inverter circuit 40 includes a W-phase circuit 43, which is formed by connecting multiple switch modules 430 in parallel, each containing multiple semiconductor switches 430s with upper and lower arms connected in series, and by connecting the connection points (AC output terminals 430O) of the upper and lower arms of each of the multiple switch modules 430. That is, the inverter circuit 40 includes a bridge circuit formed by connecting multiple output circuits (U-phase circuit 41, V-phase circuit 42, and W-phase circuit 43) in parallel for multiple phases. The inverter circuit 40 then 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. Furthermore, the inverter circuit 40 includes a positive-side DC busbar 40P that connects the positive terminals 410P, 420P, and 430P of multiple switch modules 410, 420, and 430 to each other, and a negative-side DC busbar 40N that connects the negative terminals 410N, 420N, and 430N of multiple switch modules 410, 420, and 430 to each other. The inverter circuit 40 also includes a U-phase parallel connection busbar 41O1 that connects the AC output terminals 410O of multiple switch modules 410 to each other. Furthermore, the positive-side DC busbar 40P, the negative-side DC busbar 40N, and the U-phase parallel connection busbar 41O1 have a laminate structure in which they are stacked via insulating layers 41I1 and 41I2.Similarly, the inverter circuit 40 includes a V-phase parallel connection busbar 42O1 that connects the AC output terminals 420O of multiple switch modules 420. The positive-side DC busbar 40P, the negative-side DC busbar 40N, and the V-phase parallel connection busbar 42O1 have a laminated structure in which they are laminated via insulating layers 42I1 and 42I2. Similarly, the inverter circuit 40 includes a W-phase parallel connection busbar 43O1 that connects the AC output terminals 430O of multiple switch modules 430. The positive-side DC busbar 40P, the negative-side DC busbar 40N, and the W-phase parallel connection busbar 43O1 have a laminated structure in which they are laminated via insulating layers 43I1 and 43I2. Furthermore, the connection point 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 located at a position further from the smoothing circuit 20 than the semiconductor switch 410s that is furthest from the smoothing circuit 20 among all the arms (semiconductor switches 410s) included in the multiple switch modules 410. Similarly, the connection point between the V-phase parallel connection busbar 42O1 and the wiring to the output terminal 40T (V-phase output terminal 42T) is located at a position further from the smoothing circuit 20 than the semiconductor switch 420s that is furthest from the smoothing circuit 20 among all the arms (semiconductor switches 420s) included in the multiple switch modules 420. Similarly, the connection point between the busbar 43O1 for W-phase parallel connection and the wiring to the output terminal 40T (W-phase output terminal 43T) is located further from the smoothing circuit 20 than the semiconductor switch 430s that is furthest from the smoothing circuit 20 among all the arms (semiconductor switches 430s) included in the multiple switch modules 430.

[0309] As a result, with the laminated structure of the busbars in the inverter circuit 40, the current density of all power paths between the DC input and AC input junction of the inverter circuit 40 can be made approximately uniform. Furthermore, with the arrangement of the connection between the U-phase parallel connection busbar 41O1 and the U-phase output busbar 41O2, the junction where the paths from each of the multiple switch modules 410 converge is set near the semiconductor switch 410s furthest from the smoothing circuit 20. That is, the length of all power paths between the DC input and AC output junction of the inverter circuit 40, passing through each of the multiple switch modules 410, can be made approximately equal. Therefore, the power converter 1 can make the inductance of all power paths in a complete loop between the smoothing circuit 20 and the output terminal 40T (U-phase output terminal 41T), passing through each of the multiple switch modules 410, approximately equal. Thus, the power converter 1 can suppress current imbalance in the multiple semiconductor switches 410s (switch modules 410) and achieve current uniformity. The same applies to the multiple switch modules 420. Therefore, the power converter 1 can make the inductance of the complete power path between the smoothing circuit 20 and the output terminal 40T (V-phase output terminal 42T) passing through each of the multiple switch modules 420 approximately equal. Thus, the power converter 1 can suppress current imbalance in the multiple semiconductor switches 420s (switch modules 420) and equalize the current. The same applies to the multiple switch modules 430. Therefore, the power converter 1 can make the inductance of the complete power path between the smoothing circuit 20 and the output terminal 40T (W-phase output terminal 43T) passing through each of the multiple switch modules 430 approximately equal. Thus, the power converter 1 can suppress current imbalance in the multiple semiconductor switches 430s (switch modules 430) and equalize the current.

[0310] Furthermore, 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). The connection between the U-phase parallel connection busbar 41O1 and the U-phase output busbar 41O2 may be positioned in the X-axis direction at a location further from the smoothing circuit 20 than the switch module 410 that is furthest from the smoothing circuit 20 among the multiple switch modules 410. The same may apply to the connection between the V-phase parallel connection busbar 42O1 and the V-phase output busbar 42O2, and the connection between the W-phase parallel connection busbar 43O1 and the W-phase output busbar 43O2.

[0311] For example, multiple switch modules 410 may be arranged in two groups, each aligned along the X-axis, and then arranged in two rows along another axis perpendicular to the X-axis (Y-axis). The same may apply to multiple switch modules 420 and multiple switch modules 430. The connection between the U-phase parallel connection busbar 41O1 and the U-phase output busbar 41O2 may be located in the X-axis direction at a position further away from the ends of the two groups than the smoothing circuits 20, and in the Y-axis direction approximately in the center of the two groups. The same may apply to the connection between the V-phase parallel connection busbar 42O1 and the V-phase output busbar 42O2, and the connection between the W-phase parallel connection busbar 43O1 and the W-phase output busbar 43O2.

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

[0313] Furthermore, in this embodiment (fourth embodiment), the power converter 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, which is formed by connecting multiple switch modules 410, each having upper and lower arms containing multiple semiconductor switches 410s connected in series, in parallel, and connecting the connection points (AC output terminals 410O) of the upper and lower arms of each of the multiple switch modules 410. Similarly, the inverter circuit 40 includes a V-phase circuit 42, which is formed by connecting multiple switch modules 420, each having upper and lower arms containing multiple semiconductor switches 420s connected in series, in parallel, and connecting the connection points (AC output terminals 420O) of the upper and lower arms of each of the multiple switch modules 420. Similarly, the inverter circuit 40 includes a W-phase circuit 43, which is formed by connecting multiple switch modules 430 in parallel, each containing multiple semiconductor switches 430s with upper and lower arms connected in series, and by connecting the connection points (AC output terminals 430O) of the upper and lower arms of each of the multiple switch modules 430. That is, the inverter circuit 40 includes a bridge circuit formed by connecting multiple output circuits (U-phase circuit 41, V-phase circuit 42, and W-phase circuit 43) in parallel for multiple phases. The inverter circuit 40 then 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. Furthermore, the inverter circuit 40 includes a positive-side DC busbar 40P that connects the positive terminals 410P, 420P, and 430P of multiple switch modules 410, 420, and 430 to each other, and a negative-side DC busbar 40N that connects the negative terminals 410N, 420N, and 430N of multiple switch modules 410, 420, and 430 to each other. The inverter circuit 40 also includes a U-phase parallel connection busbar 41O1 that connects the AC output terminals 410O of multiple switch modules 410 to each other. Furthermore, the positive-side DC busbar 40P, the negative-side DC busbar 40N, and the U-phase parallel connection busbar 41O1 have a laminate structure in which they are stacked via insulating layers 41I1 and 41I2.Similarly, the inverter circuit 40 includes a V-phase parallel connection busbar 42O1 that connects the AC output terminals 420O of multiple switch modules 420. The positive-side DC busbar 40P, the negative-side DC busbar 40N, and the V-phase parallel connection busbar 42O1 have a laminated structure in which they are laminated via insulating layers 42I1 and 42I2. Similarly, the inverter circuit 40 includes a W-phase parallel connection busbar 43O1 that connects the AC output terminals 430O of multiple switch modules 430. The positive-side DC busbar 40P, the negative-side DC busbar 40N, and the W-phase parallel connection busbar 43O1 have a laminated structure in which they are laminated via insulating layers 43I1 and 43I2. Furthermore, the connection point between the U-phase parallel connection busbar 41O1 and the wiring to the output terminal 40T (U-phase output terminal 41T) (U-phase output busbar 41O2) is located closer to the smoothing circuit 20 than the semiconductor switch 410s closest to the smoothing circuit 20 among all the arms (semiconductor switches 410s) included in the multiple switch modules 410. Similarly, the connection point between the V-phase parallel connection busbar 42O1 and the wiring to the output terminal 40T (V-phase output terminal 42T) (V-phase output busbar 42O2) is located closer to the smoothing circuit 20 than the semiconductor switch 420s closest to the smoothing circuit 20 among all the arms (semiconductor switches 420s) included in the multiple switch modules 420. Similarly, the connection point between the busbar 43O1 for W-phase parallel connection and the wiring (busbar 43O2 for W-phase output) to the output terminal 40T (W-phase output terminal 43T) is located 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 of the laminated structure of the busbars in the inverter circuit 40, the current density in all power paths between the DC input and AC input junction of the inverter circuit 40 can be made nearly uniform. Furthermore, due to the arrangement of the connection between the U-phase parallel connection busbar 41O1 and the U-phase output busbar 41O2, the direction of the current in the U-phase positive electrode DC busbar 41P and the direction of the current in the U-phase parallel connection busbar 41O1 can be reversed in real space. 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 electrode DC busbar 41N can be reversed. Therefore, the magnetic fields generated by currents of approximately the same current density flowing in opposite directions cancel each other out, reducing the inductance of the U-phase positive electrode DC busbar 41P, the U-phase negative electrode DC busbar 41N, and the U-phase parallel connection busbar 41O1 to a very small size. As a result, the difference in inductance of all power paths between the DC input and the AC input junction, passing through multiple switch modules 410, is reduced, and the inductance between power paths can be made uniform. Therefore, the power converter 1 can suppress and significantly reduce the difference in inductance of the complete power path between the smoothing circuit 20 and the output terminal 40T (U-phase output terminal 41T), passing through each of the multiple switch modules 410. Thus, the power converter 1 can suppress the current imbalance in the multiple semiconductor switches 410s (switch modules 410) and make the current uniform. The same applies to the multiple switch modules 420. Therefore, the power converter 1 can suppress and significantly reduce the difference in inductance of the complete power path between the smoothing circuit 20 and the output terminal 40T (V-phase output terminal 42T), passing through each of the multiple switch modules 420. Thus, the power converter 1 can suppress the current imbalance in the multiple semiconductor switches 420s (switch modules 420) and make the current uniform. The same applies to the multiple switch modules 430. Therefore, the power converter 1 can suppress and significantly reduce the inductance difference in the 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 converter 1 can suppress the current imbalance in the multiple semiconductor switches 430s (switch module 430) and equalize the current.

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

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

[0317] Specifically, this allows the direction of the current in the U-phase positive electrode DC busbar 41P and the U-phase parallel connection busbar 41O1, as well as the direction of the current in the U-phase parallel connection busbar 41O1 and the U-phase negative electrode DC busbar 41N, to be reversed in real space. Similarly, this allows the direction of the current in the V-phase positive electrode DC busbar 42P and the V-phase parallel connection busbar 42O1, as well as the direction of the current in the V-phase parallel connection busbar 42O1 and the V-phase negative electrode DC busbar 42N, to be reversed in real space. Similarly, this allows the direction of the current in the W-phase positive electrode DC busbar 43P and the W-phase parallel connection busbar 43O1, as well as the direction of the current in the W-phase parallel connection busbar 43O1 and the W-phase negative electrode DC busbar 43N, to be reversed in real space.

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

[0319] 1. Power converter 10 Rectifier circuit 20 Smoothing circuit 20I1, 20I2 insulating layer 20N Negative side busbar 20P Positive side busbar 20PN Laminate Busbar 21. Smoothing Capacitor 21P Positive terminal 21N Negative terminal 30 fuses 40 Inverter Circuit 40N negative electrode DC busbar 40P Positive DC Busbar 40PN Laminate Busbar 40T output terminal 41 U phase circuit (output circuit) 41I1, 41I2 insulating layer 41N U-phase negative electrode DC busbar 41O U-Interaction Busbar 41O1 Busbar for U-phase parallel connection 41O2 U-phase output busbar 41P U-phase positive electrode DC busbar 41PN, 41PNO U-phase laminate busbar 41T U phase output terminal 42 V phase circuit (output circuit) 42I1, 42I2 insulating layer 42N V-phase negative electrode DC busbar 42O V-phase AC busbar 42O1 Busbar for V-phase parallel connection 42O2 V-phase output busbar 42P V-phase positive electrode DC busbar 42PN, 42PNO V-phase laminate busbar 42T V phase output terminal 43 W phase circuit (output circuit) 43I1, 43I2 insulating layer 43N W-phase negative electrode DC busbar 43O W-phase AC busbar 43O1 Busbar for W-phase parallel connection 43O2 W-phase output busbar 43P W-phase positive electrode DC busbar 43PN, 43PNO W-phase laminate busbar 43T W-phase output terminal 410-416 Switch Modules (Switch Legs) 410N~416N Negative terminal 410O~416O AC output terminals (connection points) 410P~416P Positive side terminal 410s, 411s1~416s1, 411s2~416s2 Semiconductor Switches 411d1~416d1, 411d2~416d2 Circulation diodes 420-426 Switch Modules (Switch Legs) 420N~426N Negative terminal 420O~426O AC output terminal (connection point) 420P~426P Positive side terminal 420s, 421s1~426s1, 421s2~426s2 Semiconductor Switches 421d1~426d1, 421d2~426d2 Circulation diode 430-436 Switch Module (Switch Leg) 430N~436N Negative terminal 430O~436O AC output terminal (connection point) 430P~436P Positive side terminal 430s, 431s1~436s1, 431s2~436s2 Semiconductor Switches 431d1~436d1, 431d2~436d2 Circulation diode

Claims

[Claim 1] Smoothing circuit and The device includes a bridge circuit comprising a bridge circuit in which multiple switch legs, each having upper and lower arms connected in series, are connected in parallel, and output circuits, each connecting the connection points of the upper and lower arms of the multiple switch legs, are connected in parallel for multiple phases, and an inverter circuit that outputs a predetermined AC power based on the DC power input from the smoothing circuit, It includes an output terminal that outputs the predetermined AC power to the outside, The inverter circuit includes a positive-side DC busbar that connects the positive terminals of a plurality of switch legs, a negative-side DC busbar that connects the negative terminals of a plurality of switch legs, and a parallel connection busbar that connects the connection points of the upper and lower arms of each of the plurality of switch legs. The positive electrode DC busbar, the negative electrode DC busbar, and the parallel connection busbar have a laminate structure in which they are stacked with an insulating layer in between. The smoothing circuit and the inverter circuit are arranged side by side in one axial direction. The multiple switch legs are arranged in two groups, each aligned in the first axial direction, and then arranged in two rows in the other axial direction perpendicular to the first axial direction. The connection between the parallel connection busbar and the wiring to the output terminal is provided in the first axial direction at a position closer to the smoothing circuit than the ends of the two groups that are closer to the smoothing circuit. The connection points of the upper and lower arms of the respective switch legs of the two groups are connected by a single parallel connecting busbar having a flat plate shape. Power converter.

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