Common-mode filter circuit

Abstract

This common-mode filter circuit is provided with: an annular common-mode transformer core through the inside of which a secondary winding is inserted; a primary winding wound onto the common-mode transformer core so as to pass along the inner side and the outer side of the common-mode transformer core; and heat sinks through the inside of which the secondary winding is inserted and the ends of which abut and join to the common-mode transformer core, thereby exchanging heat with the common-mode transformer core. Notch sections that allow the primary winding to pass between the inner side and the outer side of the common-mode transformer core are formed in either the heat sinks or the common-mode transformer core.

Description

Common mode filter circuit

[0001] The present disclosure relates to a common mode filter circuit.

[0002] Conventionally, a common mode filter circuit has been known that includes an annular common mode transformer core through which a secondary winding is inserted, and a primary winding that is wound around the common mode transformer core so as to pass through the inside and outside of the common mode transformer core (see Patent Document 1 below).

[0003] International Publication No. 2022-118847

[0004] In this type of common mode filter circuit, the temperature of the common mode transformer core rises due to iron loss. If the common mode transformer core becomes too hot, it may become impossible to continue operation. Therefore, this disclosure describes a common mode filter circuit that can appropriately cool the common mode transformer core.

[0005] A common mode filter circuit according to one aspect of the present disclosure is [1] "a common mode filter circuit comprising: an annular common mode transformer core having a secondary winding inserted therein; a primary winding wound around the common mode transformer core so as to pass between the inside and outside of the common mode transformer core; and a cooler having the secondary winding inserted therein and joined to the common mode transformer core with ends of the secondary winding in an extending direction butting against each other, and performing heat exchange with the common mode transformer core, wherein a passage for passing the primary winding between the inside and outside of the common mode transformer core is formed in the cooler or the common mode transformer core."

[0006] According to the common mode filter circuit of the present disclosure, the common mode transformer core can be appropriately cooled.

[0007] 1A and 1B are diagrams illustrating a common mode filter circuit according to an embodiment of the present invention; FIG. 1A is a diagram illustrating the physical structure of a passive common noise canceller, and FIG. 1B is a cross-sectional view of the passive common noise canceller as viewed from below; FIG. 1C is an exploded perspective view illustrating a common mode transformer included in the passive common noise canceller; FIG. 1A is a left side view of a comb-shaped heat sink, FIG. 1B is a front view thereof, and FIG. 1C is a right side view thereof; FIG. 1C is an exploded perspective view illustrating a common mode transformer according to a modified example; FIG. 1C is an exploded perspective view illustrating a common mode transformer according to another modified example; FIG. 1C is a diagram illustrating a passive common noise canceller according to a modified example; FIG. 1C is a diagram illustrating a passive common noise canceller according to another modified example;

[0008] The gist of the present disclosure lies in the following [1] to [6].

[0009] [1] A common mode filter circuit comprising: an annular common mode transformer core through which a secondary winding is inserted; a primary winding wound around the common mode transformer core so as to pass between the inside and outside of the common mode transformer core; and a cooler through which the secondary winding is inserted and which is joined to the common mode transformer core by butting together ends of the secondary winding in an extending direction, and which exchanges heat with the common mode transformer core, wherein a passage for passing the primary winding between the inside and outside of the common mode transformer core is formed in the cooler or the common mode transformer core.

[0010] [2] The common mode filter circuit according to [1], wherein the passage path is formed in the cooler.

[0011] [3] The common mode filter circuit according to [1], wherein the passage path is a notch formed at an end of the cooler or the common mode transformer core.

[0012] [4] The common mode filter circuit according to any one of [1] to [3], wherein a plurality of the common mode transformer cores and a plurality of the coolers are arranged alternately in the extension direction of the secondary winding with their ends butted against each other.

[0013] [5] The common mode filter circuit according to any one of [1] to [4], wherein a plurality of the common mode transformer cores and a plurality of the coolers are arranged in an extending direction of the secondary winding, and some of the plurality of coolers have cooling capacities different from the others.

[0014] [6] The common mode filter circuit according to any one of [1] to [5], wherein the plurality of coolers include a first cooler located closer to the center, and a second cooler located farther from the center than the first cooler and having a lower cooling capacity than the first cooler.

[0015] [7] The common mode filter circuit according to any one of [1] to [5], wherein among the plurality of coolers, the coolers closer to the center have higher cooling capacity.

[0016] Hereinafter, embodiments will be described with reference to the drawings. Fig. 1 is a diagram showing a common mode filter circuit 10 of this embodiment. Fig. 2(a) is a diagram showing the physical structure of a passive common noise canceller 60 provided in the common mode filter circuit 10 of this embodiment. Fig. 2(b) is a cross-sectional view showing the passive common noise canceller 60 as viewed from below in Fig. 2(a). Fig. 3 is an exploded perspective view showing a common mode transformer 61 included in the passive common noise canceller 60, with a portion thereof being exploded.

[0017] 1, a common mode filter circuit 10 of this embodiment is connected between an inverter 30 and a three-phase AC motor 40. The inverter 30 has a pair of input terminals 30a, 30b connected to a power supply 20, and three output terminals 30u, 30v, and 30w that output three-phase AC. The three-phase AC motor 40 is supplied with three-phase AC from the output terminals 30u, 30v, and 30w of the inverter 30 via a motor cable 50.

[0018] The power supply 20 is a DC power supply such as a battery or a converter. The inverter 30 is, for example, a voltage-type PWM inverter. The inverter 30 converts the DC voltage supplied from the power supply 20 via input terminals 30a and 30b into a three-phase AC voltage by the switching operation of power semiconductor elements (IGBT, SiC, etc.), and outputs the three-phase AC voltage from output terminals 30u, 30v, and 30w. The AC voltage converted by the inverter 30 is supplied to the three-phase AC motor 40 via the common mode filter circuit 10 and a motor cable 50. The frame of the three-phase AC motor 40 is connected to a ground voltage via a ground wire.

[0019] The common mode filter circuit 10 includes a passive common noise canceller 60. The passive common noise canceller 60 has three common mode transformers 61, 62, and 63 that cancel out the common mode voltage of the three-phase AC. The common mode filter circuit 10 also includes three pairs of capacitors 71, 72, 73, 74, 75, and 76. The three pairs of capacitors 71, 72, 73, 74, 75, and 76 are connected to the common mode transformers 61, 62, and 63 and to the input terminals 30a and 30b of the inverter 30, respectively.

[0020] The common mode transformer 61 has a one-phase primary winding 61t and three-phase secondary windings 61u, 61v, and 61w. The common mode transformer 62 has a one-phase primary winding 62t and three-phase secondary windings 62u, 62v, and 62w. The common mode transformer 63 has a one-phase primary winding 63t and three-phase secondary windings 63u, 63v, and 63w.

[0021] One end 61a, 62a, 63a of the primary windings 61t, 62t, 63t of the three common mode transformers 61, 62, 63 are connected to the three output terminals 30u, 30v, 30w of the inverter 30. That is, one end 61a of the primary winding 61t of the common mode transformer 61 is connected to the U-phase output terminal 30u of the three-phase inverter 30. One end 62a of the primary winding 62t of the common mode transformer 62 is connected to the V-phase output terminal 30v of the three-phase inverter 30. One end 63a of the primary winding 63t of the common mode transformer 63 is connected to the W-phase output terminal 30w of the three-phase inverter 30.

[0022] The other ends 61b, 62b, and 63b of the primary windings 61t, 62t, and 63t of the three common mode transformers 61, 62, and 63 are connected to the other ends 71b, 73b, and 75b of the capacitors 71, 73, and 75, respectively. The capacitor 71 is one of the pair of capacitors 71 and 72 among the three pairs of capacitors 71, 72, 73, 74, 75, and 76. The capacitor 73 is one of the pair of capacitors 73 and 74 among the three pairs of capacitors 71, 72, 73, 74, 75, and 76. The capacitor 75 is one of the pair of capacitors 75 and 76 among the three pairs of capacitors 71, 72, 73, 74, 75, and 76. One ends 71a, 73a, and 75a of the capacitors 71, 73, and 75 are connected to the input terminal 30b, which is one of the pair of input terminals 30a and 30b of the inverter 30.

[0023] The other ends 61b, 62b, and 63b of the primary windings 61t, 62t, and 63t of the three common mode transformers 61, 62, and 63 are connected to the other ends 72b, 74b, and 76b of the capacitors 72, 74, and 76. The capacitor 72 is the other of the pair of capacitors 71 and 72 among the three pairs of capacitors 71, 72, 73, 74, 75, and 76. The capacitor 74 is the other of the pair of capacitors 73 and 74 among the three pairs of capacitors 71, 72, 73, 74, 75, and 76. The capacitor 76 is the other of the pair of capacitors 75 and 76 among the three pairs of capacitors 71, 72, 73, 74, 75, and 76. One ends 72a, 74a, and 76a of the capacitors 72, 74, and 76 are connected to the other input terminal 30a of the inverter 30, which is the other of the pair of input terminals 30a and 30b.

[0024] That is, the other end 61b of the primary winding 61t of the common mode transformer 61 connected to the U-phase of the inverter 30 is connected to the other end 71b of the capacitor 71 and the other end 72b of the capacitor 72. One end 71a of the capacitor 71 is connected to one input terminal 30b of the inverter 30. One end 72a of the capacitor 72 is connected to the other input terminal 30a of the inverter 30.

[0025] The other end 62b of the primary winding 62t of the common mode transformer 62 connected to the V-phase of the inverter 30 is connected to the other end 73b of the capacitor 73 and the other end 74b of the capacitor 74. One end 73a of the capacitor 73 is connected to one input terminal 30b of the inverter 30. One end 74a of the capacitor 74 is connected to the other input terminal 30a of the inverter 30.

[0026] The other end 63b of the primary winding 63t of the common mode transformer 63 connected to the W phase of the inverter 30 is connected to the other end 75b of the capacitor 75 and the other end 76b of the capacitor 76. One end 75a of the capacitor 75 is connected to one input terminal 30b of the inverter 30. One end 76a of the capacitor 76 is connected to the other input terminal 30a of the inverter 30. The primary windings 61t, 62t, 63t and the capacitors 71, 72, 73, 74, 75, 76 form a filter that detects the common mode voltages of the U phase, V phase, and W phase.

[0027] The three-phase secondary windings 61u, 61v, 61w, 62u, 62v, 62w, 63u, 63v, and 63w of the three common mode transformers 61, 62, and 63 are connected in series with one another. One ends 64ua, 64va, and 64wa of the three series-connected three-phase secondary windings 61u, 61v, 61w, 62u, 62v, 62w, 63u, 63v, and 63w of the three common mode transformers 61, 62, and 63 are connected to three output terminals 30u, 30v, and 30w of the inverter 30, respectively.

[0028] The three common mode transformers 61, 62, 63 are connected in series with each other, and the other ends 64ub, 64vb, 64wb of the three-phase secondary windings 61u, 61v, 61w, 62u, 62v, 62w, 63u, 63v, 63w are connected to the respective phases of the three-phase AC motor 40 via the motor cable 50.

[0029] That is, the U-phase secondary windings 61u, 62u, and 63u of the common mode transformers 61, 62, and 63 are connected in series with one another. One end 64ua of the secondary windings 61u, 62u, and 63u is connected to the U-phase output terminal 30u of the inverter 30. The other end 64ub of the secondary windings 61u, 62u, and 63u is connected to the U-phase of the three-phase AC motor 40.

[0030] V-phase secondary windings 61v, 62v, and 63v of common mode transformers 61, 62, and 63 are connected in series with one another. One end 64va of secondary windings 61v, 62v, and 63v is connected to V-phase output terminal 30v of inverter 30. The other end 64vb of secondary windings 61v, 62v, and 63v is connected to the V-phase of three-phase AC motor 40.

[0031] W-phase secondary windings 61w, 62w, and 63w of common mode transformers 61, 62, and 63 are connected in series with one another. One end 64wa of secondary windings 61w, 62w, and 63w is connected to W-phase output terminal 30w of inverter 30. The other end 64wb of secondary windings 61w, 62w, and 63w is connected to the W-phase of three-phase AC motor 40.

[0032] The ratio of the number of turns of the primary windings 61t, 62t, and 63t of each of the three common mode transformers 61, 62, and 63 to the number of turns of the secondary windings 61u, 61v, 61w, 62u, 62v, 62w, 63u, 63v, and 63w is 3:1. In this embodiment, the number of turns of the primary windings 61t, 62t, and 63t of each of the three common mode transformers 61, 62, and 63 is 3, and the number of turns of the secondary windings 61u, 61v, 61w, 62u, 62v, 62w, 63u, 63v, and 63w of each of the three common mode transformers 61, 62, and 63 is 1 (the winding only passes inside a core 65, which will be described later).

[0033] Next, the passive common noise canceller 60 will be further described with reference to Figures 2 and 3. As described above, the passive common noise canceller 60 includes three common mode transformers 61, 62, and 63. These three common mode transformers 61, 62, and 63 have the same configuration. Therefore, Figure 3 shows the common mode transformer 61 as a representative, and the configuration of the common mode transformer 61 will be described below as a representative, with redundant description of the common mode transformers 62 and 63 sometimes omitted.

[0034] 2 and 3, the common mode transformer 61 has an annular common mode transformer core 65 (hereinafter simply referred to as "core 65") made of a magnetic material. The core 65 is, for example, an iron core. The primary winding 61t of the common mode transformer 61 is wound three times by passing through an inner periphery 65i and an outer periphery 65o of the annular core 65.

[0035] Each of the secondary windings 61u, 61v, and 61w of the common mode transformer 61 is wound once by passing only once inside the inner 65i of the core 65 of the common mode transformer 61. A common mode transformer having a structure in which the secondary winding passes only once inside the core is generally sometimes called a "through-type common mode transformer" or the like.

[0036] The primary winding 61t is an electric wire made of a highly conductive metal such as copper or aluminum, covered with an insulating coating. The secondary windings 61u, 61v, and 61w are electric wires or bus bars made of a highly conductive material such as copper or aluminum.

[0037] The common mode transformer 61 also includes two heat sinks 81, 81 joined to the core 65. The heat sinks 81, 81 function as coolers for cooling the core 65. The heat sinks 81, 81 will be described in detail later.

[0038] In this common mode filter circuit 10 (FIG. 1), a U-phase secondary winding 69u, a V-phase secondary winding 69v, and a W-phase secondary winding 69w each pass in order through the insides 65i of the three cores 65 of the common mode transformers 61, 62, and 63. The three cores 65 of the common mode transformers 61, 62, and 63 are arranged in a straight line, and the secondary windings 69u, 69v, and 69w extend linearly through the three cores 65.

[0039] Of the secondary winding 69u, the portion that passes through the common mode transformer 61 is the secondary winding 61u (FIG. 1), the portion that passes through the common mode transformer 62 is the secondary winding 62u (FIG. 1), and the portion that passes through the common mode transformer 63 is the secondary winding 63u (FIG. 1).

[0040] Similarly, of secondary winding 69v, the portion that passes through common mode transformer 61 is secondary winding 61v (FIG. 1), the portion that passes through common mode transformer 62 is secondary winding 62v (FIG. 1), and the portion that passes through common mode transformer 63 is secondary winding 63v (FIG. 1).

[0041] Similarly, of secondary winding 69w, the portion that passes through common mode transformer 61 is secondary winding 61w (FIG. 1), the portion that passes through common mode transformer 62 is secondary winding 62w (FIG. 1), and the portion that passes through common mode transformer 63 is secondary winding 63w (FIG. 1).

[0042] According to the common mode filter circuit 10 as described above, the common mode voltage that may cause failure of the bearings of the three-phase AC motor 40 is reduced.

[0043] In the common mode transformers 61, 62, and 63 described above, the temperature of the core 65 rises due to iron loss. If the core 65 becomes too hot, it may become impossible to continue operation. Therefore, the common mode transformers 61, 62, and 63 are provided with a configuration for appropriately cooling the core 65. A specific configuration for appropriately cooling the core 65 in the passive common noise canceller 60 will now be described.

[0044] The secondary windings 69u, 69v, and 69w in this embodiment extend linearly within the area in which the passive common noise canceller 60 is constructed. Furthermore, as shown in Figures 2 and 3, the core 65 in this embodiment is cylindrical, and the cylindrical axis of the core 65 extends in the direction in which the secondary windings 69u, 69v, and 69w extend. In the following description, the term "axial direction" simply refers to the cylindrical axial direction of the core 65 (the direction in which the secondary windings 69u, 69v, and 69w extend).

[0045] The common mode transformer 61 includes two heat sinks 81, 81 joined to the core 65 to cool the core 65. The two heat sinks 81, 81 are arranged axially sandwiching the core 65. In this embodiment, the heat sink 81 is cylindrical with approximately the same inner and outer diameters as the core 65. The heat sink 81 is joined to the core 65 so that its cylindrical end faces face each other. That is, the heat sink 81 and the core 65 are joined so that the cylindrical end face 81a of the heat sink 81 and the cylindrical end face 65a of the core 65 are in close contact with each other. The heat sink 81 is made of a material with high thermal conductivity, such as copper or aluminum, and exchanges heat with the joined core 65. The secondary windings 69u, 69v, and 69w pass through the hollow portions of the heat sinks 81, 81 and the inside 65i of the core 65.

[0046] The heat sink 81 and the core 65 may be joined together by, for example, bonding using an adhesive. Furthermore, a thermally conductive portion (not shown) made of a thermal interface material (TIM) may be interposed between the heat sink 81 and the core 65.

[0047] In this common mode transformer 61, the primary winding 61t is wound three times around the core 65 so as to alternately pass through the inner side 65i and the outer side 65o of the core 65. Therefore, the primary winding 61t may interfere with the joint between the heat sink 81 and the core 65 between the inner side 65i and the outer side 65o of the core 65. Therefore, in order to install the primary winding 61t without interfering with the heat sink 81 and the core 65, a passage is formed between the inner side 65i and the outer side 65o of the core 65 to allow the primary winding 61t to pass through.

[0048] As a specific example of the above-mentioned passage path, a recess may be formed by recessing a portion of the circumferential direction of the cylindrical end surface 81 a of the heat sink 81. In this case, a hole of a size corresponding to the depth and width of the recess is formed between the core 65 and the heat sink 81, thereby forming the above-mentioned passage path.

[0049] 2 and 3, in this embodiment, a notch 83 is formed in the cylindrical end surface 81a of the heat sink 81, cutting out a portion of the circumferential direction. The notch 83 is dug down to a predetermined depth from the cylindrical end surface 81a and formed over a predetermined length in the circumferential direction so as to have a cross-sectional shape that allows the primary winding 61t to pass through three times. This notch 83 forms a gap between the joined heat sink 81 and core 65, allowing the primary winding 61t, which runs from the inner side 65i to the outer side 65o of the core 65, to pass through the notch 83.

[0050] The heat sinks 81 as described above are respectively joined to both cylindrical end surfaces 65a of the core 65 of the common mode transformer 61. That is, the common mode transformer 61 includes the core 65 and two heat sinks 81, 81 arranged with the core 65 sandwiched therebetween. Each heat sink 81 is joined to the core 65 so that its end surface faces each other. A notch 83 is formed in the heat sink 81, and the notch 83 functions as a passageway for the primary winding 61t between the inner side 65i and the outer side 65o of the core 65. The passive common noise canceller 60 has three common mode transformers 61, 62, 63 having the above-described configuration, and the three common mode transformers 61, 62, 63 are arranged in the axial direction.

[0051] 2 and 3 are exaggerated schematic representations of parts necessary for explaining the structure of the common mode transformer 61 of this embodiment, and do not show the exact shape or dimensions of each part. For example, although the heat sink 81 is schematically illustrated as a relatively simple cylinder in FIGS. 2 and 3, the actual heat sink 81 may have a number of thin, parallel fins. Such a heat sink with a number of fins is generally sometimes called a "comb-shaped heat sink." Furthermore, for example, the heat sink 81 may be a hollow material having a hollow portion through which a refrigerant (e.g., cooling air or cooling water) passes.

[0052] A specific example of a comb-shaped heat sink 81 is shown in Figure 4. Figure 4(a) is a left side view of the comb-shaped heat sink 81, Figure 4(b) is a front view thereof, and Figure 4(c) is a right side view thereof. This heat sink 81 is an integrally formed metal block having an annular flat base 81p and a number of fins 80q extending perpendicularly from one side of the base 81p. The other side of the base 81p forms a cylindrical end surface 81a, and a notch 83 is formed in the cylindrical end surface 81a. The depth of the notch 83 is smaller than the thickness of the base 81p. A through hole 81r is formed in the center of the heat sink 81 to allow the secondary windings 69u, 69v, and 69w to pass through.

[0053] Next, the effects of the passive common noise canceller 60 of this embodiment as described above will be described. In the common mode transformers 61, 62, and 63, the heat sinks 81, 81 joined to the core 65, exchange heat with the core 65. That is, heat from the core 65, which has become hot, is transferred to the heat sinks 81, 81. The heat transferred from the core 65 is then dissipated from the heat sinks 81 to the outside, thereby cooling the core 65. The method of dissipating heat from the heat sinks 81 to the outside, i.e., the method of cooling the heat sinks 81, 81, may be natural air cooling, forced air cooling, or water cooling. That is, a device in which the common mode filter circuit 10 is constructed may be provided with an appropriate cooling unit that cools the heat sinks 81 by one of the above methods. The specifications of the heat sink 81 may be designed according to the specifications of the cooling unit. That is, for example, if the cooling unit is an air blower and the heat sink 81 is comb-shaped, the fins of the heat sink 81 may be designed to be oriented parallel to the direction of the flow of cooling air from the cooling unit.

[0054] In this way, the passive common noise canceller 60 can appropriately cool the core 65. By appropriately designing the cooling capacity of the heat sinks 81, 81, it is possible to prevent the temperature of the core 65 from reaching the upper limit allowable for continuous operation, thereby enabling continuous operation of the common mode filter circuit 10 and the three-phase AC motor 40.

[0055] For example, if there is a difference in the tendency of temperature rise of the cores 65 during operation among the three common mode transformers 61, 62, and 63, heat sinks 81 with different specifications may be applied to each of the common mode transformers 61, 62, and 63. In other words, the cooling capacities of the heat sinks 81 included in the passive common noise canceller 60 do not all need to be the same, and heat sinks 81 with different cooling capacities may be applied to each of the cores 65 in accordance with their respective tendency of temperature rise.

[0056] For example, in passive common noise canceller 60, it is thought that the closer to the center in the arrangement direction of common mode transformers 61, 62, and 63, the more likely heat is to be trapped and the stronger the tendency for temperature to rise. Therefore, of the heat sinks 81 included in passive common noise canceller 60, the heat sink 81 (first cooler) located closer to the center may be made to have a higher cooling capacity than another heat sink 81 (second cooler) located further from the center. This allows the common mode transformers closer to the center to be cooled by the heat sink with higher cooling capacity.

[0057] For example, the cooling capacity of the heat sink may be decreased as it is positioned further from the center. More specifically, as shown in FIG. 2 , the common mode transformer 62, which is positioned in the center of the three, is sandwiched between the common mode transformers 61 and 63, and is therefore likely to trap heat and be difficult to dissipate. Therefore, the temperature of the core 65 of the common mode transformer 62 is likely to rise more easily than that of the common mode transformers 61 and 63. Therefore, heat sinks 81S, 81S with higher cooling capacity than the other heat sinks 81 may be used for the common mode transformer 62. Furthermore, when comparing the two heat sinks 81 of the common mode transformer 61, a heat sink 81T with higher cooling capacity than the other may be used for the one closer to the common mode transformer 62. Similarly, when comparing the two heat sinks 81 of the common mode transformer 63, a heat sink 81T with higher cooling capacity than the other may be used for the one closer to the common mode transformer 62. In this case, the cooling capacity of the heat sink 81S is higher than that of the heat sink 81T. In order to adjust the cooling capacity of the heat sink 81S, for example, the size of the heat sink 81S, the number and surface area of ​​the fins, or the material of the heat sink 81S may be adjusted as appropriate.

[0058] Furthermore, in order to efficiently cool the core 65 as described above, it is necessary to bring the core 65 into good contact with the heat sinks 81, 81. In contrast, according to the passive common noise canceller 60 of this embodiment, the primary winding 61t passes through the notch 83 of the heat sink 81, thereby improving the contact between the cylindrical end surface 81a of the heat sink 81 and the cylindrical end surface 65a of the core 65. In other words, the primary winding 61t does not interfere with the heat sink 81, and the entire cylindrical end surface 81a excluding the notch 83 comes into good contact with the cylindrical end surface 65a of the core 65. Therefore, the core 65 can be cooled appropriately.

[0059] The present disclosure can be implemented in various forms, including the above-described embodiments, with various modifications and improvements based on the knowledge of those skilled in the art. Furthermore, by utilizing the technical matters described in the above-described embodiments, it is also possible to configure, for example, the following modified examples. The configurations of the respective embodiments may be used in appropriate combination.

[0060] For example, instead of providing the notch 83 in the heat sink 81, a notch 66 may be provided in the cylindrical end surface 65a of the core 65 as shown in Fig. 5. The shape of the notch 66 may be the same as the above-mentioned notch 83. In the case of the configuration of Fig. 3 in which the notch 83 is provided in the heat sink 81, it is possible to suppress changes in electromagnetic performance due to changes in the shape of the core 65.

[0061] In the embodiment, a notch 83 dug to a predetermined depth from the cylindrical end surface 81a of the heat sink 81 is formed as a passage for passing the primary winding 61t, but the passage is not limited to this notch 83. For example, as shown in Fig. 6, a notch 84 formed by cutting out a portion of the circumferential direction of the heat sink 81 across the entire width in the axial direction may be formed as the passage. In this case, the heat sink 81 has a C-shape when viewed from the axial direction.

[0062] Furthermore, it is not essential that the heat sinks 81, 81 be joined to both sides of the core 65. For example, as shown in FIG. 7( a), in each of the common mode transformers 61, 62, 63, the heat sink 81 may be joined only to one cylindrical end surface 65 a of each core 65.

[0063] 7B, the heat sink 81 between adjacent cores 65 may be integrated and shared. In this case, adjacent cores 65 are joined to both ends of a single shared heat sink 81. Three cores 65 and four heat sinks 81 are joined end-to-end and arranged alternately in the axial direction. In this case, notches 83 are formed on both cylindrical end faces 81a of the heat sink 81 sandwiched between the cores 65. This configuration allows the common mode transformers 61, 62, and 63 to be positioned closer to each other in the axial direction, thereby making the passive common noise canceller 60 more compact overall. Furthermore, sharing the heat sink 81 in this manner reduces the number of components.

[0064] Furthermore, in the configuration in which the cores 65 and heat sinks 81 are arranged alternately as described above, the heat sink 81 at one end of the arrangement may be omitted, resulting in a configuration such as that shown in FIG. 8( a), for example. In this case, three cores 65 and three heat sinks 81 are arranged alternately. Furthermore, the heat sinks 81 at both ends of the arrangement may be omitted, resulting in a configuration such as that shown in FIG. 8( b), for example. In this case, three cores 65 and two heat sinks 81 are arranged alternately.

[0065] Furthermore, the shapes of the core 65 and the heat sink 81 are not limited to a cylindrical shape as long as they are annular and allow the secondary windings 69u, 69v, and 69w to be inserted therethrough. For example, the shapes of the core 65 and the heat sink 81 may be an elliptical annular shape or a rectangular annular shape when viewed in the direction in which the secondary windings 69u, 69v, and 69w extend.

[0066] As described above, the secondary windings 69u, 69v, and 69w may be electric wires or bus bars. There are no restrictions on the arrangement of the three secondary windings 69u, 69v, and 69w, as long as they are inserted inside the core 65 and the heat sink 81. Furthermore, the secondary windings 69u, 69v, and 69w may extend linearly or may be curved.

[0067] When the secondary windings 69u, 69v, 69w are bus bars, an insulator may be provided on the inner wall surface of the heat sink 81 to prevent electrical conduction between the heat sink 81 and the secondary windings 69u, 69v, 69w. Furthermore, the core 65 and the heat sink 81 are not limited to being integrally formed members, and may be composed of multiple parts divided in the circumferential direction.

[0068] The heat sink 81 in the above-described embodiment has a cylindrical shape with approximately the same inner and outer diameters as the core 65, but the shape of the heat sink 81 is not limited to the above as long as the ends of the heat sink 81 are abutted against each other in the axial direction to enable heat exchange with the core 65. For example, the heat sink 81 may protrude from the core 65 when viewed in the axial direction.

[0069] 10 Common mode filter circuit 60 Passive common noise canceller 61, 62, 63 Common mode transformer 61t, 62t, 63t Primary winding 69u, 69v, 69w Secondary winding 65 Core (common mode transformer core) 65a Cylindrical end surface 65i Inside 65o Outside 81 Heat sink (cooler) 81a Cylindrical end surface 66, 83, 84 Notch portion (passage path)

Claims

1. A common mode filter circuit comprising: an annular common mode transformer core through which a secondary winding is inserted; a primary winding wound around the common mode transformer core so as to pass between the inside and outside of the common mode transformer core; and a cooler through which the secondary winding is inserted and which is joined to the common mode transformer core by butting together ends of the secondary winding in the extension direction, and which exchanges heat with the common mode transformer core, wherein a passage for passing the primary winding between the inside and outside of the common mode transformer core is formed in the cooler or the common mode transformer core.

2. The common mode filter circuit according to claim 1, wherein the passage path is formed in the cooler.

3. The common mode filter circuit according to claim 1, wherein the passage path is a notch formed at an end of the cooler or the common mode transformer core.

4. A common mode filter circuit according to claim 1, wherein a plurality of said common mode transformer cores and a plurality of said coolers are arranged with their ends butted against each other and alternately arranged in the direction in which said secondary winding extends.

5. The common mode filter circuit according to claim 1, wherein a plurality of said common mode transformer cores and a plurality of said coolers are arranged in the direction in which said secondary winding extends, and the plurality of said coolers include those having cooling capacities different from one another.

6. A common mode filter circuit as described in claim 5, wherein the plurality of coolers include a first cooler located closer to the center, and a second cooler located further from the center than the first cooler and having a lower cooling capacity than the first cooler.

7. The common mode filter circuit according to claim 5, wherein the coolers arranged closer to the center have higher cooling capacity.

Images