Three-phase composite common inductor

Abstract

As a result, a three-phase composite common inductor is provided that can suppress the occurrence of magnetic saturation even in large current applications. [Solution] A three-phase composite common inductor 1 that acts as a common inductance for common currents and as a normal inductance for normal currents, comprising a first core 2, a second core 3, and a U-phase coil 4U, a V-phase coil 4V, and a W-phase coil 4W wound around the first core 2, with the second core 3 being formed from a material with lower magnetic permeability than the first core 2.

Description

[Technical Field]

[0001] The present invention relates to a three-phase compound common inductor. [Background technology]

[0002] Patent Document 1 discloses a three-phase composite common inductor (dual mode choke coil) that acts as a common inductance (common mode noise filter) for common currents and as a normal inductance (normal mode noise filter) for normal currents. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020 / 144795 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the three-phase compound common inductor described in Patent Document 1, a gap is provided in each of the three closed magnetic circuits for normal inductance, and the magnetic resistance of each closed magnetic circuit is set based on the gap dimension, which poses the problem that the setting range of the magnetic resistance is limited due to factors such as leakage magnetic flux.In addition, in the three-phase compound common inductor described in Patent Document 1, part of the core (second magnetic core) protrudes outward, which causes the volume to expand and makes it difficult to reduce the size. [Means for solving the problem]

[0005] The present invention has been made in view of the above-described circumstances and with the object of solving these problems. The invention of claim 1 is a three-phase compound common inductor that acts as a common inductance for a common current and as a normal inductance for a normal current, comprising a first core, a second core, and a first phase coil, a second phase coil, and a third phase coil wound around the first core, wherein the first core comprises a first leg portion and a second leg portion that are parallel to each other, a first connecting portion that connects one ends of the first leg portion and the second leg portion together, and a second connecting portion that connects the other ends of the first leg portion and the second leg portion together, and at least one of the first leg portion and the second leg portion is provided with the first phase coil, the second phase coil, and the third phase coil in this order from one end to the other end. a third leg portion and a fourth leg portion that are parallel to each other and connect intermediate portions of the first leg portion and the second leg portion; the first phase coil, the second phase coil, and the third phase coil are edgewise coils formed by winding a rectangular wire at a right angle; the first phase coil is wound around at least one of the first leg portion and the second leg portion between the first connecting portion and the third leg portion; the second phase coil is wound around at least one of the first leg portion and the second leg portion between the third leg portion and the fourth leg portion; and the third phase coil is wound around at least one of the first leg portion and the second leg portion between the fourth leg portion and the second connecting portion; and the second core is formed of a material having a lower magnetic permeability than the first core. Furthermore, the invention of claim 2 is a three-phase composite common inductor according to claim 1, characterized in that the first core is a ferrite core, and the second core is a dust core having a lower magnetic permeability than the ferrite core. The invention of claim 3 is the three-phase compound common inductor according to claim 1, characterized in that the first core is formed by connecting two U-shaped cores. Furthermore, the invention of claim 4 is a three-phase composite common inductor according to claim 1, characterized in that the first core is formed by connecting two U-shaped cores via two I-shaped cores. The invention of claim 5 is a three-phase composite common inductor according to claim 4, characterized in that a gap is provided between the U-shaped core and the I-shaped core to adjust the balance of the three-phase normal inductance. The invention of claim 6 is a three-phase composite common inductor according to claim 1, wherein the second core further comprises a first plate portion arranged along the inner circumferential surface of the first leg portion and a second plate portion arranged along the inner circumferential surface of the second leg portion, one end of the third leg portion is connected to the first leg portion via the first plate portion, the other end of the third leg portion is connected to the second leg portion via the second plate portion, one end of the fourth leg portion is connected to the first leg portion via the first plate portion, and the other end of the fourth leg portion is connected to the second leg portion via the second plate portion. Furthermore, the invention of claim 7 is a three-phase composite common inductor according to claim 1, characterized in that the second core further comprises a first auxiliary leg portion arranged along the side surface of the third leg portion and connecting the side surfaces of the middle portions of the first leg portion and the second leg portion, and a second auxiliary leg portion arranged along the side surface of the fourth leg portion and connecting the side surfaces of the middle portions of the first leg portion and the second leg portion. [Effects of the Invention]

[0006] According to the invention of claim 1, a closed magnetic circuit for common inductance is formed by the first leg, second leg, first connecting portion, and second connecting portion of the first core; a closed magnetic circuit for first-phase normal inductance is formed by the first leg, second leg, and first connecting portion of the first core and the third leg of the second core; a closed magnetic circuit for second-phase normal inductance is formed by the first leg and second leg of the first core and the third and fourth leg of the second core; and a closed magnetic circuit for third-phase normal inductance is formed by the first leg, second leg, and second connecting portion of the first core and the fourth leg of the second core. Furthermore, because the second core is made of a material with lower magnetic permeability than the first core, a large magnetic reluctance can be set in the closed magnetic circuit for normal inductance without providing a gap. As a result, a three-phase compound common inductor can be provided that can suppress magnetic saturation even in high-current applications. Furthermore, the first, second and third phase coils are edgewise coils made by winding rectangular wire at right angles, which not only increases the coil density and enables the three-phase composite common inductor to be made smaller, but also flattens the outer shape of each coil, improving adhesion to the cooling member. Furthermore, according to the invention of claim 2, the first core is a ferrite core and the second core is a dust core which has a lower magnetic permeability than a ferrite core, so that a three-phase composite common inductor applicable to large current applications can be constructed using inexpensive ferrite cores and dust cores. Furthermore, according to the invention of claim 3, the first core is formed by connecting two U-shaped cores, so that a three-phase compound common inductor applicable to large current applications can be constructed using inexpensive U-shaped cores. Furthermore, according to the invention of claim 4, the first core is formed by connecting two U-shaped cores via two I-shaped cores, which not only makes it possible to configure a three-phase composite common inductor that is applicable to large current applications using inexpensive U-shaped and I-shaped cores, but also makes it easy to extend the lengths of the first and second legs. Furthermore, according to the invention of claim 5, a gap is provided between the U-shaped core and the I-shaped core to adjust the balance of the three-phase normal inductance, thereby preventing a decrease in performance due to an imbalance in the three-phase normal inductance. Furthermore, according to the invention of claim 6, the second core further includes a first plate portion and a second plate portion arranged along the inner surfaces of the first leg portion and the second leg portion, and the third leg portion and the fourth leg portion are connected to the first leg portion and the second leg portion via the first plate portion and the second plate portion, thereby increasing the contact area between the first core and the second core and suppressing magnetic saturation at the contact portion between the first core and the second core. Furthermore, according to the invention of claim 7, the second core further includes a first auxiliary leg and a second auxiliary leg that are arranged along the side surfaces of the third leg and the fourth leg and connect the side surfaces of the middle portions of the first leg and the second leg, thereby increasing the contact area between the first core and the second core and suppressing magnetic saturation at the contact portion between the first core and the second core. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a perspective view of a three-phase compound common inductor according to an embodiment of the present invention; [Figure 2] 1A is a perspective view of a first core, FIG. 1B is a perspective view of a second core, and FIG. 1C is a perspective view showing the state in which the second core is assembled to the first core. [Figure 3] 1A is a perspective view of the U-phase coil, the V-phase coil, and the W-phase coil, and FIG. 1B is a perspective view of the bobbin. [Figure 4] 1A and 1B are diagrams illustrating a structure of a three-phase compound common inductor; [Figure 5] (a) is a diagram showing the basic structure of a three-phase compound common inductor, and (b) is the magnetic equivalent circuit of the three-phase compound common inductor. [Figure 6] (a) is a diagram showing the flow of magnetic flux when a common current is input to a three-phase compound common inductor, and (b) is the magnetic equivalent circuit when a common current is input to a three-phase compound common inductor. [Figure 7] 10 is an explanatory diagram of a normal current input to a three-phase compound common inductor. FIG. [Figure 8] (a) is a diagram showing the flow of magnetic flux when a normal current is input to a three-phase compound common inductor, and (b) is the magnetic equivalent circuit when a normal current is input to a three-phase compound common inductor. [Figure 9] FIG. 10 is a diagram schematically showing the structure of a three-phase compound common inductor according to a first modified example. [Figure 10] 10(a) is a diagram schematically showing a core structure of a three-phase compound common inductor according to a second modified example, and FIG. 10(b) is a diagram schematically showing a core structure of a three-phase compound common inductor according to a third modified example. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Basic configuration of a three-phase compound common inductor] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In Figures 1 to 4, reference numeral 1 denotes a three-phase composite common inductor, which acts as a common inductance for common currents and as a normal inductance for normal currents. For example, the three-phase composite common inductor 1 is used as a dual-mode noise filter that reduces common-mode noise and normal-mode noise in large-current applications such as large-capacity battery charging circuits, large-capacity power conditioner circuits, motor drive circuits for electric vehicles, and compressor drive circuits for hydrogen fuel cells.

[0009] As shown in FIGS. 1 to 4, the three-phase compound common inductor 1 includes a first core 2, a second core 3, a U-phase coil 4U, a V-phase coil 4V, a W-phase coil 4W, and a bobbin 5.

[0010] The first core 2 includes a first leg 21 and a second leg 22 arranged in parallel with each other, a first connecting portion 23 connecting one ends of the first leg 21 and the second leg 22, and a second connecting portion 24 connecting the other ends of the first leg 21 and the second leg 22. A U-phase coil 4U, a V-phase coil 4V, and a W-phase coil 4W are wound around at least one of the first leg 21 and the second leg 22 in this order from one end to the other end.

[0011] The second core 3 has a third leg 31 and a fourth leg 32 that are parallel to each other and connect the middle portions of the first leg 21 and the second leg 22. The second core 3 is made of a material with lower magnetic permeability than the first core 2.

[0012] The U-phase coil 4U is wound around at least one of the first leg 21 and the second leg 22 between the first connecting portion 23 and the third leg 31. The V-phase coil 4V is wound around at least one of the first leg 21 and the second leg 22 between the third leg 31 and the fourth leg 32. The W-phase coil 4W is wound around at least one of the first leg 21 and the second leg 22 between the fourth leg 32 and the second connecting portion 24.

[0013] According to such a three-phase composite common inductor 1, the first leg 21, the second leg 22, the first connecting portion 23, and the second connecting portion 24 of the first core 2 form a closed magnetic circuit for the common inductance (hereinafter, sometimes referred to as a common closed magnetic circuit); the first leg 21, the second leg 22, and the first connecting portion 23 of the first core 2 and the third leg 31 of the second core 3 form a closed magnetic circuit for the U-phase normal inductance (hereinafter, sometimes referred to as a U-phase normal closed magnetic circuit); the first leg 21 and the second leg 22 of the first core 2 and the third leg 31 and the fourth leg 32 of the second core 3 form a closed magnetic circuit for the V-phase normal inductance (hereinafter, sometimes referred to as a V-phase normal closed magnetic circuit); and the first leg 21, the second leg 22, and the second connecting portion 24 of the first core 2 and the fourth leg 32 of the second core 3 form a closed magnetic circuit for the W-phase normal inductance (hereinafter, sometimes referred to as a W-phase normal closed magnetic circuit).

[0014] Furthermore, since the second core 3 is formed from a material with a lower magnetic permeability than the first core 2, a large magnetic resistance can be set in the closed magnetic circuit for normal inductance without providing a gap, resulting in a three-phase composite common inductor 1 that can suppress the occurrence of magnetic saturation even in high-current applications.

[0015] [Basic operation of a three-phase compound common inductor] Next, the basic operation of the three-phase compound common inductor 1 based on the three-phase compound common inductor 1 having the basic configuration shown in FIG. 5 will be described with reference to FIGS.

[0016] However, in Figs. 5 to 8, i u , i v , i w are the input currents of each coil 4U, 4V, and 4W, R1 to R4 are the magnetic resistances of each part of the first core 2, and R a is the magnetic resistance of the third leg 31, R b is the magnetic resistance of the fourth leg 32, n is the number of turns of each of the coils 4U, 4V, and 4W, and ni u is the flux source of U phase, ni v is the flux source of V phase, ni w is the W-phase magnetic flux source, φ u is the magnetic flux generated by U-phase coil 4U, φ v is the magnetic flux generated by the V-phase coil 4V, φ w is the magnetic flux generated by the W-phase coil 4W.

[0017] (common inductance) Figure 6(a) shows the flow of magnetic flux when a common current is input to a three-phase compound common inductor, and Figure 6(b) shows the magnetic equivalent circuit when a common current is input to a three-phase compound common inductor. As shown in Fig. 6(a), when a common current is input simultaneously to the three-phase coils 4U, 4V, and 4W, the magnetic flux φ generated by each of the coils 4U, 4V, and 4W is u , φ v , φ w The magnetic flux flows in the direction shown by the dotted line in Fig. 6(a). The main magnetic flux direction is the direction shown by the thick dotted line in Fig. 6(a), and each magnetic flux φ u , φv , φ w Since each of the magnetic fluxes flows in the same direction, the total magnetic flux φ is expressed as follows:

[0018]

number

[0019] Also, as shown by the thin dotted lines in Figure 6(a), each magnetic flux φ u , φ v , φ w A part of the magnetic current also flows through the third leg 31 and the fourth leg 32 of the second core 3, but the magnetic permeability of the second core 3 is sufficiently lower (for example, 1 to 2%) than that of the first core 2, and the magnetic resistance R of the third leg 31 and the fourth leg 32 a , R b is much larger than the magnetic resistances R1 to R4 of each part of the first core 2, the magnetic flux flowing through the third leg 31 and the fourth leg 32 due to the common current is at a substantially negligible level. Therefore, the amount of magnetic flux φ generated by each of the coils 4U, 4V, and 4W due to the common current is u , φ v , φ w Then, the common inductance L is expressed as the following [Equation 2] and [Equation 3].

[0020]

number

[0021]

number

[0022] (normal inductance) Figure 7 is an explanatory diagram of the normal current input to a three-phase compound common inductor, Figure 8(a) is a diagram showing the flow of magnetic flux when a normal current is input to a three-phase compound common inductor, and Figure 8(b) is a magnetic equivalent circuit when a normal current is input to a three-phase compound common inductor. As shown in Figure 7, the three-phase AC current waveforms are shifted in phase by 120° from each other, so the sum of the three-phase currents is zero at any timing. Also, the sum of the currents of any two of the three phases has the same value as the current of the remaining phase, but flows in the opposite direction. For example, the dotted waveform in Figure 7 shows that the U-phase current i u and V-phase current i v This current is the sum of the W-phase current i w The value is the same as, but in the opposite direction.

[0023] As shown in Figure 8(a), when normal current is input to the three-phase coils 4U, 4V, and 4W, the magnetic flux φ generated by the coils 4U, 4V, and 4W of each phase is u , φ v , φ w flow through the U-phase normal closed magnetic circuit, the V-phase normal closed magnetic circuit, and the W-phase normal closed magnetic circuit, respectively. For example, as shown in the magnetic equivalent circuit in FIG. 9, when attention is focused on the U-phase coil 4U, the magnetic flux φ generated by the U-phase coil 4U due to the normal current is u does not flow through the V-phase normal closed magnetic circuit and the W-phase normal closed magnetic circuit, but flows through the U-phase normal closed magnetic circuit, so the U-phase current i u As a result, the normal inductance L of the U-phase coil 4U u(Normal) is expressed as the following [Equation 4].

[0024]

number

[0025] Here, AL a is the AL value of the third leg 31. In other words, the normal inductance L of the U-phase coil 4U is calculated by the magnetic resistances R1 and Ra included in the U-phase normal closed magnetic circuit. u(Normal) Furthermore, when the core cross-sectional area is Ae, the magnetic flux density B of the U-phase normal closed magnetic circuit is given by the following [Equation 5].

[0026]

number

[0027] When B < Bs (Bs: saturation magnetic flux density of the first core 2 and the second core 3), since the first core 2 does not saturate magnetically, the magnetic resistance R of the second core 3 a is designed to be large, so that even at a higher normal current, magnetic saturation can be avoided while maintaining a predetermined normal inductance Lu(Normal) and a design with a higher normal impedance becomes possible. Similarly, the normal inductances L of the other two phases v(Normal) , the normal inductance L w(Normal) and the normal impedance can also be designed. However, in the V-phase normal closed magnetic circuit, there are two magnetic resistances R a , R b due to the third leg 31 and the fourth leg 32, so the normal inductance L of the V-phase v(Normal) is as shown in [Equation 6] below.

[0028]

Equation

[0029]

Equation

[0030] [Configuration of Coil, First Core and Second Core] Next, the configurations of the coils 4U, 4V, 4W, the first core 2 and the second core 3 will be described with reference to FIGS. 1 to 4.

[0031] 1 and 3, each of the coils 4U, 4V, and 4W is an edgewise coil formed by winding a rectangular wire at a right angle. In this embodiment, each of the coils 4U, 4V, and 4W includes a first winding portion 4a wound around the first leg 21, a second winding portion 4b wound around the second leg 22, and a connecting portion 4c connecting the first winding portion 4a and the second winding portion 4b. However, each of the coils 4U, 4V, and 4W may be wound around either the first leg 21 or the second leg 22. Each of the coils 4U, 4V, and 4W is housed in a resin bobbin 5 and assembled to the first core 2.

[0032] The first core 2 is made of, for example, a ferrite core, and the second core 3 is made of, for example, a dust core having a lower magnetic permeability than a ferrite core. For example, the magnetic permeability of the second core 3 is set to about 1 to 2% of the magnetic permeability of the first core 2.

[0033] The first core 2 is formed by connecting two U-shaped cores 2b via two I-shaped cores 2a. In this way, the first core 2 can be configured with long first leg 21 and second leg 22 without using a special U-shaped core with long legs.

[0034] The second core 3 further includes a first plate portion 33 disposed along the inner circumferential surface of the first leg portion 21 and a second plate portion 34 disposed along the inner circumferential surface of the second leg portion 22. One end of the third leg portion 31 is connected to the first leg portion 21 via the first plate portion 33, and the other end of the third leg portion 31 is connected to the second leg portion 32 via the second plate portion 34. One end of the fourth leg portion 32 is connected to the first leg portion 21 via the first plate portion 33, and the other end of the fourth leg portion 32 is connected to the second leg portion 22 via the second plate portion 34. The first plate portion 33 and the second plate portion 34 are made of the same core material as the third leg portion 31 and the fourth leg portion 32, and the contact areas with the first leg portion 21 and the second leg portion 22 are larger than the contact areas with the third leg portion 31 and the fourth leg portion 32.

[0035] The second core 3 further includes a first auxiliary leg 35 that is arranged along the side surface of the third leg 31 and connects the side surfaces of the middle portions of the first leg 21 and the second leg 22, and a second auxiliary leg 36 that is arranged along the side surface of the fourth leg 32 and connects the side surfaces of the middle portions of the first leg 21 and the second leg 22. The first plate 33 and the second plate 34 are made of the same core material as the third leg 31 and the fourth leg 32.

[0036] [Effects of the embodiment] According to the present embodiment configured as described above, a closed magnetic circuit for common inductance is formed by the first leg 21, the second leg 22, the first connecting portion 23, and the second connecting portion 24 of the first core 2, a closed magnetic circuit for U-phase normal inductance is formed by the first leg 21, the second leg 22, and the first connecting portion 23 of the first core 2 and the third leg 31 of the second core 3, a closed magnetic circuit for V-phase normal inductance is formed by the first leg 21 and the second leg 22 of the first core 2 and the third leg 31 and the fourth leg 32 of the second core 3, and a closed magnetic circuit for W-phase normal inductance is formed by the first leg 21, the second leg 22, and the second connecting portion 24 of the first core 2 and the fourth leg 32 of the second core 3. The second core 3 is formed of a material with a lower magnetic permeability than the first core 2, so that a large magnetic resistance can be set in the closed magnetic circuit for normal inductance without providing a gap. As a result, it is possible to provide a three-phase composite common inductor 1 that can suppress the occurrence of magnetic saturation even in large current applications.

[0037] Furthermore, the first core 2 is a ferrite core and the second core 3 is a dust core which has a lower magnetic permeability than a ferrite core, so that a three-phase composite common inductor 1 applicable to large current applications can be constructed using inexpensive ferrite cores and dust cores.

[0038] Furthermore, the U-phase coil 4U, V-phase coil 4V, and W-phase coil 4W are edgewise coils made by winding rectangular wire at right angles, which not only increases the coil density and enables the three-phase composite common inductor 1 to be made smaller, but also flattens the outer shape of each coil 4U, 4V, and 4W, improving adhesion to the cooling member.

[0039] Furthermore, since the first core 2 is formed by connecting two U-shaped cores 2b via two I-shaped cores 2a, not only can a three-phase composite common inductor 1 applicable to large current applications be constructed using inexpensive U-shaped cores 2b and I-shaped cores 2a, but the lengths of the first leg 21 and second leg 22 can also be easily extended.

[0040] In addition, the second core 3 further includes a first plate portion 33 and a second plate portion 34 arranged along the inner surfaces of the first leg portion 21 and the second leg portion 22, and the third leg portion 31 and the fourth leg portion 32 are connected to the first leg portion 21 and the second leg portion 22 via the first plate portion 33 and the second plate portion 34, thereby increasing the contact area between the first core 2 and the second core 3 and suppressing magnetic saturation at the contact portion between the first core 2 and the second core 3.

[0041] In addition, the second core 2 further includes a first auxiliary leg 35 and a second auxiliary leg 36 that are arranged along the side surfaces of the third leg 31 and the fourth leg 32 and connect the side surfaces of the middle portions of the first leg 21 and the second leg 22, thereby increasing the contact area between the first core 2 and the second core 3 and suppressing magnetic saturation at the contact portion between the first core 2 and the second core 3.

[0042] [Variations] Next, a modified example of the three-phase compound common inductor 1 will be described with reference to Fig. 9 and Fig. 10. However, for configurations common to the above-described embodiment, the same reference numerals as those in the above-described embodiment will be used, and the description of the above-described embodiment may be used.

[0043] FIG. 9 is a diagram schematically showing the structure of a three-phase compound common inductor according to a first modified example. The first modified example differs from the above-described embodiment in that the first core 2 is formed by connecting two U-shaped cores 2b. According to the first modified example, a three-phase compound common inductor 1 applicable to large current applications can be configured using inexpensive U-shaped cores 2b.

[0044] FIG. 10(a) is a diagram schematically showing the core structure of a three-phase compound common inductor according to a second modified example, and FIG. 10(b) is a diagram schematically showing the core structure of a three-phase compound common inductor according to a third modified example. The second and third modified examples differ from the above-described embodiment in that a gap 37 is provided between the U-shaped core 2b and the I-shaped core 2a to adjust the balance of the three-phase normal inductance. According to the second and third modified examples, it is possible to prevent a decrease in performance due to an imbalance in the three-phase normal inductance. For example, the U-phase normal closed magnetic circuit and the W-phase normal closed magnetic circuit have a magnetic resistance R of either the third leg 31 or the fourth leg 32. a , R b However, the V-phase normal closed magnetic circuit has two magnetic resistances R due to the third leg 31 and the fourth leg 32. a , R b Since there is a magnetic resistance R due to the gap 37 in the U-phase normal closed magnetic circuit and the W-phase normal closed magnetic circuit, g This can eliminate the imbalance in the three-phase normal inductance.

[0045] The present invention is not limited to the above-described embodiment, and various modifications and changes are possible within the scope of the claims. [Explanation of symbols]

[0046] 1 Three-phase composite common inductor 2. First Core 21 1st leg 22 Second leg 23 1st connection part 24 2nd connection part 2a I-shaped core 2b U-shaped core 3 Second Core 31 Third leg 32 4th leg 33 1st plate part 34 2nd plate part 35 1st auxiliary leg 36 2nd auxiliary leg 37 Gap 4U U-phase coil (first phase coil) 4V V-phase coil (2nd phase coil) 4W W-phase coil (3rd phase coil) 4a Winding part 4b Winding section 4c connection part 5 bobbins

Claims

1. A three-phase composite common inductor that acts as a common inductance for a common current and as a normal inductance for a normal current, A first core; A second core; a first phase coil, a second phase coil, and a third phase coil wound around the first core, The first core is a first leg portion and a second leg portion arranged parallel to each other; a first connecting portion that connects one end of the first leg portion and one end of the second leg portion; a second connecting portion that connects the other end portions of the first leg portion and the second leg portion to each other, the first phase coil, the second phase coil, and the third phase coil are wound around at least one of the first leg portion and the second leg portion in this order from one end side to the other end side, the second core includes a third leg portion and a fourth leg portion that are parallel to each other and connect intermediate portions of the first leg portion and the second leg portion, the first phase coil, the second phase coil, and the third phase coil are edgewise coils formed by winding rectangular wire at right angles, the first phase coil is wound around at least one of the first leg and the second leg between the first connecting portion and the third leg, the second phase coil is wound around at least one of the first leg and the second leg between the third leg and the fourth leg, the third phase coil is wound around at least one of the first leg portion and the second leg portion between the fourth leg portion and the second connecting portion, The three-phase compound common inductor is characterized in that the second core is formed of a material having a lower magnetic permeability than the first core.

2. 2. The three-phase compound common inductor according to claim 1, wherein the first core is a ferrite core, and the second core is a dust core having a lower magnetic permeability than the ferrite core.

3. The three-phase compound common inductor according to claim 1 , wherein the first core is formed by connecting two U-shaped cores.

4. The three-phase compound common inductor according to claim 1 , wherein the first core is formed by connecting two U-shaped cores via two I-shaped cores.

5. 5. The three-phase compound common inductor according to claim 4, wherein a gap is provided between the U-shaped core and the I-shaped core to adjust the balance of the three-phase normal inductance.

6. The second core is a first plate portion disposed along an inner peripheral surface of the first leg portion; a second plate portion disposed along an inner circumferential surface of the second leg portion, one end of the third leg portion is connected to the first leg portion via the first plate portion, the other end of the third leg is connected to the second leg via the second plate portion, one end of the fourth leg portion is connected to the first leg portion via the first plate portion, The three-phase compound common inductor according to claim 1 , wherein the other end of the fourth leg is connected to the second leg via the second plate portion.

7. The second core is a first auxiliary leg portion disposed along a side surface of the third leg portion and connecting side surfaces of intermediate portions of the first leg portion and the second leg portion; 2. The three-phase compound common inductor according to claim 1, further comprising a second auxiliary leg portion arranged along a side surface of the fourth leg portion and connecting side surfaces of intermediate portions of the first leg portion and the second leg portion.

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