Common mode filter circuit

Abstract

This common mode filter circuit comprises: an annular core through which a secondary winding is inserted; a primary winding wound around the core so as to pass through the inside and outside of the core; and a heat sink joined to an outer peripheral surface of the core. The core has a flat shape having a longitudinal direction and a lateral direction when viewed from the Z direction. The heat sink is joined to a core longitudinal portion present along the longitudinal direction of the outer peripheral surface. The primary winding is wound around a core lateral portion present along the lateral direction of the outer peripheral surface.

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 into which a secondary winding is inserted; a primary winding wound around the common mode transformer core so as to pass through the inside and outside of the common mode transformer core; and a cooler joined to an outer peripheral surface of the common mode transformer core, wherein the common mode transformer core has a flat shape having a longitudinal direction and a lateral direction when viewed from the insertion direction of the secondary winding, the cooler is joined to a portion of the outer peripheral surface that exists along the longitudinal direction, and the primary winding is wound around a portion of the outer peripheral surface that exists along the lateral direction."

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

[0007] 1A to 1C 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 diagram illustrating the same as viewed from the direction of arrow IIb in FIG. 1A; FIG. 1C is a perspective view illustrating a common mode transformer included in the passive common noise canceller; FIG. 1A to 1C are diagrams illustrating passive common noise cancellers according to modified examples; and FIG. 1A to 1C are diagrams illustrating passive common noise cancellers according to other modified examples.

[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 through the inside and outside of the common mode transformer core; and a cooler joined to an outer peripheral surface of the common mode transformer core, wherein the common mode transformer core has a flat shape having a longitudinal direction and a lateral direction when viewed from the insertion direction of the secondary winding, the cooler is joined to a portion of the outer peripheral surface that exists along the longitudinal direction, and the primary winding is wound around a portion of the outer peripheral surface that exists along the lateral direction.

[0010] [2] The common mode filter circuit according to [1], wherein a plurality of the secondary windings are present and the plurality of secondary windings are arranged in the longitudinal direction.

[0011] [3] The common mode filter circuit according to [2], wherein the primary winding is wound around the common mode transformer core at a position aligned with the plurality of secondary windings in the longitudinal direction.

[0012] [4] The common mode filter circuit according to any one of [1] to [3], wherein there are a plurality of the common mode transformer cores arranged in an insertion direction of the secondary winding, and one of the coolers is joined to the outer peripheral surfaces of the plurality of the common mode transformer cores.

[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 joined in order and arranged alternately in the short side direction, and the secondary winding extends so as to pass inside the plurality of the common mode transformer cores.

[0014] 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 diagram showing the passive common noise canceller 60 as viewed from the direction of arrow IIb in Fig. 2(a). Fig. 3 is a perspective view showing a common mode transformer 61 included in the passive common noise canceller 60.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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).

[0031] The passive common noise canceller 60 will be further described below 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 descriptions of the common mode transformers 62 and 63 sometimes omitted.

[0032] 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.

[0033] 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.

[0034] The primary winding 61t is an electric wire made of a highly conductive metal such as copper or aluminum, and is 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.

[0035] 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.

[0036] 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.

[0037] 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).

[0038] 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).

[0039] 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).

[0040] 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.

[0041] 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.

[0042] In this embodiment, the secondary windings 69u, 69v, and 69w extend linearly within the area in which the passive common noise canceller 60 is constructed. As shown in FIGS. 2 and 3 , the core 65 has a flat shape having a longitudinal direction and a lateral direction when viewed from the insertion direction of the secondary windings 69u, 69v, and 69w. Specifically, the core 65 in this embodiment has a cylindrical shape extending in the insertion direction of the secondary windings 69u, 69v, and 69w, and has a rectangular shape with rounded corners (rounded rectangle) when viewed from the insertion direction of the secondary windings 69u, 69v, and 69w. The secondary windings 69u, 69v, and 69w are arranged in the longitudinal direction of the rounded rectangle, extend parallel to each other, and pass through an inside 65i of the core 65. In the following, the longitudinal direction of the rounded rectangle is the Y direction, the lateral direction is the X direction, and the insertion direction of the secondary windings 69u, 69v, and 69w is the Z direction, and X, Y, and Z may be used to explain the positional relationship of each part.

[0043] When viewed from the Z direction, the core 65 has a rounded rectangular shape and includes two portions extending linearly in the Y direction, two portions extending linearly in the X direction, and four rounded corners between these portions. Hereinafter, the portion of the core 65 that extends linearly in the Y direction when viewed from the Z direction will be referred to as the "core longitudinal portion" and denoted by the symbol "65y." The core longitudinal portion 65y is a flat portion that has its thickness in the X direction and is parallel to the YZ plane. Furthermore, the portion of the core 65 that extends linearly in the X direction when viewed from the Z direction will be referred to as the "core transverse portion" and denoted by the symbol "65x." The core transverse portion 65x is a flat portion that has its thickness in the Y direction and is parallel to the XZ plane.

[0044] 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 to sandwich the core 65 in the X direction and extend beyond the core 65 in the X direction. The heat sink 81 and the core 65 are joined so that the surface of the heat sink 81 is in close contact with the outer peripheral surface 65s of the core 65. 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 heat sink 81 and the core 65 may be joined by bonding, for example, using an adhesive. 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. The heat sinks 81, 81 are electrically insulated from the primary winding 61t and the secondary windings 69u, 69v, and 69w.

[0045] In this embodiment, the heat sink 81 has a rectangular parallelepiped shape and is joined to the outer peripheral surface 65s of the core longitudinal portion 65y. The dimensions of the heat sink 81 in the Y and Z directions are approximately equal to the dimensions of the core longitudinal portion 65y in the Y and Z directions, and the heat sink 81 is provided over almost the entire core longitudinal portion 65y.

[0046] The dimensions of the heat sink 81 in the Y and Z directions may be larger or smaller than the dimensions of the core longitudinal portion 65y in the Y and Z directions. If the dimension of the heat sink 81 in the Y direction is larger than the core longitudinal portion 65y, both ends of the heat sink 81 in the Y direction may protrude from the core longitudinal portion 65y in the Y direction. In this case, a gap in the X direction may be provided between the protruding portions and the rounded corners of the core 65.

[0047] The heat sinks 81 as described above are respectively joined to the two core longitudinal portions 65y 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.

[0048] The primary winding 61t of the common mode transformer 61 is wound around the core short portion 65x. That is, the primary winding 61t is wound three times around the core short portion 65x so as to pass alternately between the inner side 65i and the outer side 65o of the core 65. Therefore, the primary winding 61t does not interfere with the heat sink 81 disposed in the core long portion 65y. The primary winding 61t is wound around the core short portion 65x in a position aligned in the Y direction with the three secondary windings 69u, 69v, and 69w. In this way, the secondary windings 69u, 69v, and 69w are arranged in the Y direction and pass through the inner side 65i of the core 65, and the winding portion of the primary winding 61t is aligned in the Y direction with the secondary windings 69u, 69v, and 69w. This arrangement allows the common mode transformer 61 to be made compact.

[0049] The passive common noise canceller 60 has three common mode transformers 61, 62, and 63 having the above-described configuration, and the three common mode transformers 61, 62, and 63 are arranged in the Z direction.

[0050] 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 illustrated as a relatively simple rectangular parallelepiped 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.

[0051] Next, the effects of the common mode filter circuit 10 of this embodiment 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 incorporating the common mode filter circuit 10 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 then 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.

[0052] In this way, the common mode filter circuit 10 can appropriately cool the core 65. Furthermore, 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 allowable upper limit.

[0053] 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.

[0054] For example, it is not essential that the heat sinks 81, 81 are joined to both sides of the core 65. For example, as shown in FIG. 4( a), in each of the common mode transformers 61, 62, 63, the heat sink 81 may be joined to only one of the core longitudinal portions 65y of each core 65.

[0055] 4(b), the heat sinks 81, 81 joined to the three cores 65 of each common mode transformer 61, 62, 63 may be integrated into a common heat sink. In this case, one heat sink 81 extends to a length three times or more the Z-direction dimension of the core 65 and is joined to the core longitudinal portions 65y of the three cores 65. Sharing the heat sink 81 in this way reduces the number of parts. Even in this case, as shown in FIG. 4(c), the heat sink 81 may be provided on only one of the core longitudinal portions 65y of each core 65.

[0056] Alternatively, as shown in FIG. 5A, three common mode transformers 61, 62, and 63 may be arranged in the X direction. In this case, the secondary windings 69u, 69v, and 69w are laid along an S-shaped path so that they pass through the inner sides 65i of the three cores 65 in order. In this case, the secondary windings 69u, 69v, and 69w pass through the cores 65 of the common mode transformers 61 and 63 in opposite directions to the core 65 of the common mode transformer 62. Correspondingly, the primary windings 61t and 63t of the common mode transformers 61 and 63 are wound in opposite directions around the core 65 to the primary winding 62t of the common mode transformer 62. Note that the three secondary windings 69u, 69v, and 69w pass through one core 65 in the same direction. In the configuration shown in FIG. 5A, the heat sink 81 between the cores 65 adjacent to each other in the X direction is integrated and shared. Both opposing surfaces of a single shared heat sink 81 are joined to the outer circumferential surfaces 65s of the core longitudinal portions 65y of the two cores 65. The three cores 65 and four heat sinks 81 are joined in order and arranged alternately in the X direction. Sharing the heat sink 81 in this way reduces the number of parts.

[0057] 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, for example, as shown in FIG. 5B. 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, for example, as shown in FIG. 5C. In this case, three cores 65 and two heat sinks 81 are arranged alternately.

[0058] Furthermore, the shape of the core 65 may be annular with a flat cross section that allows the secondary windings 69u, 69v, and 69w to be inserted therethrough, and is not limited to a rounded rectangular cross section. For example, the core 65 and the heat sink 81 may be annular, rectangular, or oval when viewed in the Z direction. Even in this case, the heat sink 81 may be joined to a portion of the outer peripheral surface 65s of the core 65 that extends along the longitudinal direction. Furthermore, the primary winding 61t may be wound around a portion of the outer peripheral surface 65s that extends along the short side so as not to interfere with the heat sink 81. If the portion of the outer peripheral surface 65s that extends along the longitudinal direction of the core 65 is curved rather than flat, the joining surface of the heat sink 81 may be formed to match the curved shape of the curved surface.

[0059] 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. Furthermore, the secondary windings 69u, 69v, and 69w may extend linearly or may be curved.

[0060] The core 65 and the heat sink 81 are not limited to being integrally formed members, but may be composed of a plurality of parts divided in the circumferential direction.

[0061] 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) 65y Core long portion 65x Core short portion 65s Outer circumferential surface 65i Inside 65o Outside 81 Heat sink (cooler)

Claims

1. A common mode filter circuit comprising: an annular common mode transformer core into 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 joined to an outer peripheral surface of the common mode transformer core, wherein the common mode transformer core has a flat shape having a longitudinal direction and a lateral direction when viewed from the insertion direction of the secondary winding, the cooler is joined to a portion of the outer peripheral surface that exists along the longitudinal direction, and the primary winding is wound around a portion of the outer peripheral surface that exists along the lateral direction.

2. A common mode filter circuit as claimed in claim 1, wherein there are a plurality of said secondary windings, the plurality of said secondary windings being arranged in the longitudinal direction.

3. The common mode filter circuit according to claim 2, wherein the primary winding is wound around the common mode transformer core at a position aligned in the longitudinal direction with respect to the plurality of secondary windings.

4. The common mode filter circuit according to claim 1, wherein there are a plurality of the common mode transformer cores arranged in the insertion direction of the secondary winding, and one of the coolers is joined to the outer circumferential surfaces of the plurality of the common mode transformer cores.

5. A common mode filter circuit as claimed in claim 1, comprising: a plurality of said common mode transformer cores arranged in the short side direction; and said cooler arranged between said plurality of said common mode transformer cores and joined to each of said plurality of said common mode transformer cores, wherein said secondary winding extends so as to pass inside said plurality of said common mode transformer cores.

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