Power conversion device for railway vehicle

Abstract

A power conversion device (50) comprises: a three-phase inverter (4) that converts direct-current power to alternating-current power for a propulsion motor (15); and a magnetic core (8). The magnetic core (8) comprises: first and second cores (8a, 8b) that are passed through both a three-phase alternating-current power line (5) and a common-mode current return line (6); and a third core (8c) that is passed through only the three-phase alternating-current power line (5). The first core (8a) is arranged on the three-phase inverter (4) side, the second core (8b) is arranged on the propulsion motor (15) side, and the third core (8c) is arranged between the first core (8a) and the second core (8b). When led out to the propulsion motor (15) side from the second core (8b) of the first, second, and third cores (8a–8c), at least one electrical wiring of the three electrical wirings that constitute the three-phase alternating-current power line (5) is led out so as not to be parallel to one or two of the other electrical wirings.

Description

Power conversion equipment for railway vehicles

[0001] The present disclosure relates to a power conversion device for a railway vehicle for driving a traction motor mounted on the railway vehicle.

[0002] Power conversion devices include switching elements such as IGBTs (Insulated Gate Bipolar Transistors) and MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors). In recent power conversion devices, switching elements have become higher in voltage resistance and higher in frequency, leading to increased switching voltages and faster switching operations.

[0003] It is generally known that switching operations in power conversion devices cause common-mode currents, which are zero-phase currents. It is also known that switching operations in power conversion devices cause leakage currents to flow to the ground via parasitic capacitance between the ground and the AC power lines connecting the power conversion device to a load. It is also known that switching operations in power conversion devices cause leakage currents to flow to peripheral devices other than the load via parasitic capacitance between the AC power lines and the housing that houses the power conversion device. These leakage currents are common-mode currents that flow in the grounding system and are distinguished from zero-phase currents.

[0004] As described above, an increase in switching voltage and a speed-up of switching operation increase zero-phase current and leakage current, and increase radiated noise and conducted noise, which can have a negative effect on surrounding communication devices and the like.

[0005] In order to reduce zero-phase current, it has been conventional to wind AC power lines around or pass them through the same magnetic core. Furthermore, Patent Document 1 listed below discloses a technology for reducing leakage current by connecting the ground terminal of a power conversion device and the ground terminal of a load with an electrical wiring called a common-mode current return line, and winding the AC power line and the common-mode current return line around or passing them through the same magnetic core.

[0006] Japanese Patent Application Laid-Open No. 2001-086734

[0007] When the technology of Patent Document 1 is used, the impedance of the return loop of the ground circuit is larger than the impedance of the return loop of the common-mode current return line, thereby reducing the leakage current flowing through the return loop of the ground circuit. However, it is explained that when the technology of Patent Document 1 is used, the peak value of the zero-phase current is larger than when only the AC power line is wound around or passed through the same magnetic core. As mentioned above, the zero-phase current causes radiated noise and conducted noise. In the case of a power conversion device for a railway vehicle, an extremely large current flows through the traction motor, which is the load, so an increase in the zero-phase current cannot be tolerated.

[0008] The present disclosure has been made in view of the above, and has an object to provide a power conversion device for a railway vehicle that can reduce leakage current while preventing an increase in zero-phase current.

[0009] In order to solve the above-mentioned problems and achieve the object, a power conversion device for a railway vehicle according to the present disclosure is a power conversion device for a railway vehicle for driving a traction motor mounted on the railway vehicle, and includes a three-phase inverter that converts DC power into AC power for the traction motor, and a magnetic core through which a three-phase AC power line and a common-mode current return line pass. The three-phase AC power line is electrical wiring connecting the three-phase inverter and the traction motor, and the common-mode current return line is electrical wiring connecting the ground potential of the power conversion device and the ground potential of the traction motor. The magnetic core has first and second cores through which both the three-phase AC power line and the common-mode current return line pass, and a third core through which only the three-phase AC power line passes. The first core is located on the side of the three-phase inverter, and the second core is located on the side of the traction motor. The third core is also located between the first and second cores. In each of the first, second and third cores, the surface facing the three-phase inverter is defined as the first surface, and the surface facing the propulsion motor is defined as the second surface. When at least one of the three electrical wires constituting the three-phase AC power line is drawn out from the second core to the second surface, it is not parallel to the other one or two electrical wires.

[0010] The power conversion device for a railway vehicle according to the present disclosure has the effect of reducing leakage current while preventing an increase in zero-phase current.

[0011] 7 is a diagram showing an example of the configuration of an electrical system of a railway vehicle system including a power conversion device according to embodiment 1; FIG. 8 is a diagram showing an example of a variation of the input circuit unit shown in FIG. 1; FIG. 9 is a diagram explaining the configuration of a magnetic core provided in the power conversion device according to embodiment 1 and its positional relationship with a three-phase AC power line and a common mode current return line; FIG. 10 is a diagram explaining the effect when a magnetic core provided in the power conversion device according to embodiment 1 is used; FIG. 11 is a diagram showing an example of the configuration of a magnetic core according to embodiment 1 used in electromagnetic field analysis; FIG. 12 is a diagram showing an example of the configuration of a magnetic core shown as a comparative example of FIG. 5;

[0012] A power conversion device for a railway vehicle according to an embodiment of the present disclosure (hereinafter, abbreviated as "power conversion device" as appropriate) will be described in detail below with reference to the accompanying drawings. Note that in the accompanying drawings, the scale of each component may differ from the actual scale for ease of understanding. The same applies to the various drawings. Furthermore, in the following description, physical connection and electrical connection will not be distinguished from each other, and will be simply referred to as "connection." In other words, the term "connection" includes both a case where components are directly connected to each other and a case where components are indirectly connected to each other via other components.

[0013] Embodiment 1. Fig. 1 is a diagram showing an example of the configuration of an electrical system of a railway vehicle system including a power conversion device 50 according to embodiment 1. The power conversion device 50 according to embodiment 1 includes a filter capacitor 3, a three-phase inverter 4, and a magnetic core 8. In Fig. 1, an input circuit unit 2 is connected to the input terminal of the three-phase inverter 4, and at least one traction motor 15 is connected to the output terminal of the three-phase inverter 4. The traction motor 15 is a three-phase motor that provides propulsive force to the railway vehicle.

[0014] The input circuit unit 2 is configured to include at least a switch and a filter reactor. One end of the input circuit unit 2 is connected to an overhead line 10 via a current collector 11, and the other end is connected to a rail 12 at ground potential via wheels 13. DC or AC power supplied from the overhead line 10 is input to one end of the input circuit unit 2 via the current collector 11. A DC voltage generated by the DC power at the output end of the input circuit unit 2 is applied to a three-phase inverter 4. A filter capacitor 3 smoothes the DC voltage applied to the three-phase inverter 4 so that ripples in the DC voltage are reduced. The three-phase inverter 4 converts the DC power supplied via the input circuit unit 2 into AC power for the propulsion motor 15.

[0015] The three-phase inverter 4 is connected to the propulsion motor 15 via a three-phase AC power line 5 through a magnetic core 8. The three-phase AC power line 5 is electrical wiring that connects the three-phase inverter 4 and the propulsion motor 15. A housing (not shown) of the propulsion motor 15 is grounded by a grounding wire 7. The propulsion motor 15 is also connected to a portion of the power conversion device 50 that is at ground potential by a common mode current return line 6. The common mode current return line 6 is electrical wiring that electrically connects the ground potential of the power conversion device 50 and the ground potential of the propulsion motor 15.

[0016] The three-phase inverter 4 includes multiple switching elements 4a connected in a three-phase bridge configuration. The switching elements 4a have freewheeling diodes connected in anti-parallel. The switching elements 4a perform switching operations in response to gate signals output from a control unit (not shown). The switching operations of the switching elements 4a intermittently control the current flowing through the switching elements 4a. This converts DC power supplied from the input circuit unit 2 into AC power for the traction motor 15. The traction motor 15 is driven by AC power supplied from the three-phase inverter 4 and provides propulsion power to a train composed of one or more railway cars (not shown). The three-phase inverter 4 drives the traction motor 15 by converting DC power supplied via the input circuit unit 2 into AC power for the traction motor 15. Note that while FIG. 1 illustrates the input circuit unit 2 and the three-phase inverter 4 as separate components, they may also be housed in the same housing.

[0017] Fig. 2 is a diagram showing an example of a variation of the input circuit unit 2 shown in Fig. 1. Fig. 2 shows an input circuit unit 2A as an example in which the overhead line 10 is an AC overhead line. The input circuit unit 2A includes a main transformer 21 and a converter 22. The main transformer 21 steps down the AC voltage received via the current collector 11 and applies it to the converter 22. The converter 22 converts the stepped-down AC voltage into a DC voltage and applies it to the three-phase inverter 4.

[0018] Next, the configuration and connection of the magnetic core 8 will be described with reference to Fig. 1 and Fig. 3. Fig. 3 is a diagram illustrating the configuration of the magnetic core 8 provided in the power conversion device 50 according to the first embodiment and the positional relationship with the three-phase AC power line 5 and the common mode current return line 6.

[0019] The magnetic core 8 is composed of a first core 8a arranged on the side of the three-phase inverter 4, a second core 8b arranged on the side of the traction motor 15, and a third core 8c arranged between the first core 8a and the second core 8b. The first core 8a, the second core 8b, and the third core 8c are formed in a circular ring shape as shown in Fig. 3. It goes without saying that the term "circular" here does not only mean a perfect circle, but also includes an elliptical shape.

[0020] Furthermore, when the surface of each core consisting of the first core 8a, the second core 8b, and the third core 8c facing the three-phase inverter 4 is defined as a first surface and the surface facing the traction motor 15 is defined as a second surface, these first and second surfaces are positioned within the yz plane. Both the three-phase AC power lines 5 and the common mode current return line 6 pass through the first core 8a and the second core 8b. On the other hand, of the three-phase AC power lines 5 and the common mode current return line 6, only the three-phase AC power line 5 passes through the third core 8c. The reason for this configuration will be described later.

[0021] The three-phase AC power line 5 is made up of electrical wirings 5a, 5b, and 5c. For example, the electrical wiring 5a is a U-phase electrical wiring, the electrical wiring 5b is a V-phase electrical wiring, and the electrical wiring 5c ​​is a W-phase electrical wiring.

[0022] 1 and 3 illustrate a configuration in which each of the cores includes one first core 8a, one second core 8b, and one third core 8c, but the number of the first cores 8a, the second cores 8b, and the third cores 8c may be two or more. Also, while FIG. 3 illustrates a case in which each core is formed in a circular ring shape, this shape is not limiting. Each core may also be formed in a square ring shape. Furthermore, when each core is formed in a square ring shape, the four corners of each core may be chamfered.

[0023] Ferrite and amorphous, for example, can be used as the material of the magnetic core 8. Furthermore, the parameters of the outer circumferential length, inner circumferential length, thickness, aspect ratio, etc. of each core constituting the magnetic core 8 can be selected appropriately depending on the capacity of the three-phase inverter 4 and the length, thickness, and arrangement of the three-phase AC power lines 5. Furthermore, the magnetic permeability of the magnetic core 8 can be selected appropriately depending on the switching frequency, the stray capacitance between the power conversion device 50 and the propulsion motor 15 and the ground, and the like.

[0024] Next, the effects of using the magnetic core 8 provided in the power conversion device 50 according to the first embodiment will be described with reference to Fig. 4. Fig. 4 is a diagram for explaining the effects of using the magnetic core 8 provided in the power conversion device 50 according to the first embodiment.

[0025] 4 , a zero-phase current flows from left to right in the three-phase AC power line 5, and a zero-phase current flows from right to left in the common-mode current return line 6. In this case, a magnetic flux 100, indicated by a two-dot chain line, is generated in the first core 8a, the second core 8b, and the third core 8c through which the three-phase AC power line 5 passes, according to the right-hand screw rule. Furthermore, a magnetic flux 110, indicated by a one-dot chain line, is generated in the first core 8a and the second core 8b through which the common-mode current return line 6 passes. Because the magnetic flux 100 and the magnetic flux 110 are directed in opposite directions in the first core 8a and the second core 8b, they cancel each other out, resulting in a low magnetic flux density inside the first core 8a and the second core 8b. This makes it possible to significantly increase the level of zero-phase current at which the first core 8a and the second core 8b become magnetically saturated, compared to when only the three-phase AC power line 5 is passed through the first core 8a and the second core 8b.

[0026] Next, the reason why the common-mode current return line 6 is not passed through the third core 8c will be explained. As explained above, a zero-phase current flows in the three-phase AC power line 5 from left to right on the paper, and a zero-phase current flows in the common-mode current return line 6 from right to left on the paper. Meanwhile, there is also an operating mode in which a current flows in the common-mode current return line 6 in the same direction as the current flowing in the three-phase AC power line 5 and returns through the grounding wire 7. Although the current in this operating mode is smaller than the zero-phase current, it flows in a direction that adds magnetic flux, thereby affecting the magnetic flux density inside the magnetic core 8. To minimize this effect, the common-mode current return line 6 is not passed through the third core 8c. This configuration prevents the impedance of the return loop of the common-mode current return line 6 from becoming extremely small compared to the impedance of the return loop of the grounding circuit including the grounding wire 7. This has the effect of preventing an increase in zero-phase current while reducing leakage current.

[0027] Next, another effect provided by the magnetic core 8 of embodiment 1 will be described with reference to Figures 5 to 7, which show configuration examples and results of electromagnetic field analysis performed on a configuration including the magnetic core 8 of embodiment 1. Figure 5 is a diagram showing an example of the configuration of the magnetic core according to embodiment 1 used in the electromagnetic field analysis. Figure 6 is a diagram showing an example of the configuration of a magnetic core shown as a comparative example to Figure 5. Figure 7 is a diagram used to explain the electromagnetic field analysis performed on the magnetic cores of the configurations of Figures 5 and 6.

[0028] Fig. 5 shows an example of a configuration in which there are two first cores 8a and two second cores 8b, through which both the three-phase AC power lines 5 and the common-mode current return line 6 pass, and four third cores 8c, through which only the three-phase AC power lines 5 pass. The first cores 8a, the second cores 8b, and the third cores 8c have the same core structure. Each core member is rectangular and annular, as shown in the upper part of Fig. 7, and has a width of 150 mm in the z-direction. Note that the z-axis direction in Fig. 7 is shown in the opposite direction to that in Figs. 3 and 4.

[0029] In addition, in the comparative example shown in FIG. 6 , the total number of core members is the same, 8, but the number of core members through which only the three-phase AC power lines 5 pass and the number of core members through which both the three-phase AC power lines 5 and the common mode current return line 6 pass are equally set to 4.

[0030] The middle and lower parts of Figure 7 show the results of the electromagnetic field analysis. The horizontal axis represents the position in the z-direction, and the vertical axis represents the magnitude of the magnetic field. In the configuration of Figure 5, the core member analyzed is core member 90, which is located at the outermost end of the first core 8a. In the configuration of Figure 6, the core member analyzed is core member 92, which is located at the outermost end of the four magnetic cores through which only the three-phase AC power line 5 passes. The middle part of Figure 7 shows the magnetic field distribution along line A-A' in the magnetic core, and the lower part shows the magnetic field distribution along line B-B' in the magnetic core. In both figures, the thick solid line represents the magnetic field distribution in the configuration of the comparative example, and the thin solid line represents the magnetic field distribution in the configuration of embodiment 1. 7, an AC current with an amplitude of 70 / 3 [A] and a frequency of 100 kHz is applied to the three electrical wirings in the three-phase AC power line 5, and an AC current with an amplitude of 70 [A] and a frequency of 100 kHz is applied to the common mode current return line 6. The relative permeability of the core member is set to 4000.

[0031] As shown in the analysis results in the middle part of Figure 7, it can be seen that the peak value of the magnetic field on line A-A' in the configuration of embodiment 1 is reduced by approximately 100 (A / m) compared to the configuration of the comparative example. Also, as shown in the analysis results in the lower part of Figure 7, it can be seen that the peak value of the magnetic field on line B-B' in the configuration of embodiment 1 is reduced by approximately 130 to 140 (A / m) compared to the configuration of the comparative example. Also, as shown in the analysis results in the middle and lower parts of Figure 7, it can be seen that in the case of embodiment 1, the magnitude of the magnetic field is lower than that of the comparative example in most regions in the z-axis direction.

[0032] Next, the reason why the analysis result shown in Fig. 7 is obtained will be explained. Fig. 8 is a diagram for explaining the reason why the analysis result shown in Fig. 7 is obtained.

[0033] When three-phase AC power lines 5 are drawn from a power conversion device 50, the three-phase AC power lines 5 may be connected to a terminal block as a relay point for external wiring, for the purpose of fixing or insulating the lines, as shown in FIG. 8 . Furthermore, when the power conversion device 50 is configured for use in a railway vehicle, the three-phase AC power lines 5 are often flat, and the electrical wiring for each phase is often spaced apart at the terminal block. In this case, some of the electrical wiring for each phase is bent and drawn out from the magnetic core 8 when drawn into the terminal block. Magnetic flux from the bent and drawn out electrical wiring may remain without being canceled out, generating local magnetic flux around the magnetic core 8. FIG. 8 illustrates a situation in which local magnetic flux is generated when the electrical wiring for each phase drawn out from the magnetic core located at the outermost end is unraveled.

[0034] 5 and 6 , the flat three-phase AC power lines 5 are bent and drawn out from the core members 90 and 92 located at the outermost ends of the core members 90 and 92 under analysis. This causes local magnetic flux to be generated in the core members 90 and 92. In the core member 90 of FIG. 5 , through which the common-mode current return conductor 6 passes, part of the local magnetic flux is canceled out by the magnetic flux due to the current flowing through the common-mode current return conductor 6. In contrast, in the core member 92 of FIG. 6 , through which the common-mode current return conductor 6 does not pass, the local magnetic flux remains uncancelled. This is why the core member 90 of the first embodiment generates a smaller magnetic field than the core member 92 of the comparative example.

[0035] Therefore, by using the magnetic core 8 of the first embodiment, it is possible to suppress an increase in the magnetic field inside the magnetic core 8, thereby reducing the probability of magnetic saturation. Also, by using the magnetic core 8 of the first embodiment, it is possible to reduce the probability of magnetic saturation, thereby reducing the decrease in the magnetic permeability of the magnetic core 8 due to magnetic saturation.

[0036] As described above, the power conversion device for a railway vehicle according to the first embodiment includes a three-phase inverter that converts DC power into AC power for a traction motor mounted on the railway vehicle, and a magnetic core through which a three-phase AC power line and a common-mode current return line pass. The three-phase AC power line is electrical wiring connecting the three-phase inverter and the traction motor, and the common-mode current return line is electrical wiring connecting the ground potential of the power conversion device and the ground potential of the traction motor. The magnetic core includes first and second cores through which both the three-phase AC power line and the common-mode current return line pass, and a third core through which only the three-phase AC power line passes. The first core is located on the side of the three-phase inverter, the second core is located on the side of the traction motor, and the third core is located between the first and second cores.

[0037] As described above, the power conversion device for a railway vehicle according to the first embodiment has first and second cores through which both the three-phase AC power lines and the common-mode current return line pass, and a third core between the first and second cores through which only the three-phase AC power lines of the three-phase AC power lines and the common-mode current return line pass. This configuration prevents the impedance of the return loop of the common-mode current return line from becoming extremely small compared to the impedance of the return loop of the grounding circuit including the grounding line. This makes it possible for the power conversion device according to the first embodiment to reduce leakage current while preventing an increase in zero-phase current.

[0038] As described above, the power conversion device for a railway vehicle according to the first embodiment is configured such that the first and second cores, through which both the three-phase AC power lines and the common-mode current return line pass, are disposed at both ends of the third core, through which only the three-phase AC power lines pass. This configuration makes it possible to suppress an increase in the magnetic field of the core members located at the outermost ends of the first and second cores, thereby reducing the probability of magnetic saturation occurring in the magnetic cores and making it possible to suppress a decrease in the magnetic permeability of the magnetic cores due to magnetic saturation.

[0039] Second Embodiment In a second embodiment, a configuration for further reducing the local magnetic flux described in the first embodiment will be described.

[0040] FIG. 9 is a diagram showing the situation in which the local magnetic flux described in the first embodiment is generated on the configuration diagram of the magnetic core 8 in FIG.

[0041] 9 shows a state in which the electrical wires 5a and 5c of the three electrical wires 5a, 5b, and 5c constituting the three-phase AC power line 5 are drawn out from the first core 8a toward the first surface side so as not to be parallel to the electrical wire 5b. Also, FIG. 9 shows a state in which the electrical wires 5a and 5c of the three electrical wires 5a, 5b, and 5c constituting the three-phase AC power line 5 are drawn out from the second core 8b toward the second surface side so as not to be parallel to the electrical wire 5b. In FIG. 9, the same elements as those in FIG. 4 are designated by the same reference numerals.

[0042] 9 also shows magnetic flux 100 generated by the current flowing in the three-phase AC power line 5 and magnetic flux 110 generated by the current flowing in the common mode current return line 6, and also shows, by dashed lines, local magnetic flux 120 that may be generated by portions of the electrical wiring 5a, 5c that are not parallel to the electrical wiring 5b. As described above, magnetic flux 100 and magnetic flux 110 are opposite in direction to each other and therefore cancel each other out. In contrast, there is no canceling magnetic flux for the local magnetic flux 120, so its components remain around the first core 8a and the second core 8b or enter the interiors of the first core 8a and the second core 8b.

[0043] Therefore, in the second embodiment, the configuration of the magnetic core 81 shown in Fig. 10 is proposed. Fig. 10 is a diagram for explaining the configuration of the magnetic core 81 provided in the power conversion device 50 according to the second embodiment. In Fig. 10, the same elements as those in Fig. 9 are denoted by the same reference numerals.

[0044] 10, in the magnetic core 81 of the second embodiment, a non-magnetic metal plate 200 is provided on the first surface of the first core 8a, and a non-magnetic metal plate 200 is also provided on the second surface of the second core 8b. An example of the non-magnetic metal plate 200 is an aluminum plate.

[0045] 10 , the non-magnetic metal plate 200 is disposed on the yz plane of the first core 8 a and the second core 8 b, and therefore interlinks with the local magnetic flux 120. When the local magnetic flux 120 interlinks with the non-magnetic metal plate 200, an eddy current flows in the non-magnetic metal plate 200. This eddy current generates a magnetic flux in a direction that cancels out the local magnetic flux 120, and therefore acts to prevent the local magnetic flux 120 from entering the first core 8 a and the second core 8 b. This makes it possible to prevent the magnetic core 81 from becoming magnetically saturated by the local magnetic flux 120.

[0046] When the power conversion device 50 is used for a railway vehicle, the dimensional constraints on the traction motor 15 side are greater than those on the three-phase inverter 4 side, and there is often less free space. For this reason, it is preferable to install the non-magnetic metal plate 200 on the second surface of the second core 8b. Furthermore, when a flat three-phase AC power line 5 is used, it is difficult to extend all three electrical wirings 5a, 5b, and 5c that make up the three-phase AC power line 5 parallel to each other and secure them to a terminal block. For this reason, it goes without saying that it is also more preferable to install the non-magnetic metal plate 200 on the first surface of the first core 8a on the three-phase inverter 4 side.

[0047] 10 illustrates an example in which two of the three electrical wirings 5a, 5b, and 5c are not parallel to the other electrical wiring 5b, but this is not limiting. Even when, for example, one electrical wiring 5a of the three electrical wirings 5a, 5b, and 5c is not parallel to the other two electrical wirings 5b, 5c, the effect of reducing the local magnetic flux 120 can be achieved by providing the nonmagnetic metal plate 200. That is, as long as at least one of the three electrical wirings 5a, 5b, and 5c constituting the three-phase AC power line 5 is drawn from the first core 8a to the first surface side or from the second core 8b to the second surface side so as not to be parallel to the other one or two electrical wirings, the effect of reducing the local magnetic flux 120 by the nonmagnetic metal plate 200 can be achieved.

[0048] Embodiment 3 In embodiment 3, a preferred thickness of the non-magnetic metal plate 200 in a magnetic core 81 configured as shown in Fig. 10 will be described. Specifically, in a power conversion device 50 according to embodiment 3, it is proposed that the thickness of the non-magnetic metal plate 200 in the magnetic core 8 be equal to or greater than the skin depth.

[0049] The skin depth in a metal plate is the distance at which an electromagnetic field incident on a certain metal material is attenuated to 1 / e (≒ 1 / 2.718 ≒ -8.7 dB). Here, if the magnetic permeability of the non-magnetic metal plate 200 is μ, the electrical conductivity is σ, and the frequency is f, the skin depth δ is given by δ = 1 / √(πfμσ).

[0050] If the thickness of the non-magnetic metal plate 200 in the magnetic core 81 is set to be equal to or greater than the skin depth of the material of the non-magnetic metal plate 200, the amount of magnetic flux entering the first core 8a and the second core 8b can be reduced to 1 / e or less compared to when there is no non-magnetic metal plate 200. This makes it possible to configure the magnetic core 81 in a way that makes magnetic saturation less likely to occur.

[0051] Fourth Embodiment. Figure 11 is a diagram illustrating the configuration of a magnetic core 82 included in a power conversion device 50 according to a fourth embodiment. The magnetic core 82 shown in Figure 11 differs from the magnetic core 81 shown in Figure 10 in that a fourth core 8d, through which only the three-phase AC power line 5 passes, is added between the first core 8a and the third core 8c. The magnetic core 82 shown in Figure 11 also differs from the magnetic core 81 shown in Figure 10 in that a fifth core 8e, through which only the three-phase AC power line 5 passes, is added between the second core 8b and the third core 8c. The magnetic core 82 shown in Figure 11 also includes non-magnetic metal plates 300 on the second surface of the first core 8a, the first surface of the fourth core 8d, the second surface of the fifth core 8e, and the first surface of the second core 8b. An example of the non-magnetic metal plate 300 is an aluminum plate. 11, the non-magnetic metal plate 200 shown in Fig. 10 is not provided on the first surface of the first core 8a and the second surface of the second core 8b, but the non-magnetic metal plate 200 may be provided as in Fig. 10. The effect of including the non-magnetic metal plate 200 is the same as in the second embodiment.

[0052] Next, the effects of using the nonmagnetic metal plate 300 will be described. First, because the common-mode current return line 6 does not pass through the fourth core 8d, the third core 8c, and the fifth core 8e, it is bent between the first core 8a and the fourth core 8d and between the fifth core 8e and the second core 8b, as indicated by the dashed lines, and routed inside the magnetic core 82. This routing configuration generates local magnetic flux at the bent portions, as described in the second embodiment. In the fourth embodiment, the nonmagnetic metal plate 300 is provided to prevent such local magnetic flux from penetrating the first core 8a and the fourth core 8d, and the fifth core 8e and the second core 8b. By providing the nonmagnetic metal plate 300, it is possible to prevent magnetic saturation of the magnetic core 82 due to local magnetic flux that may be generated at the bent portions of the common-mode current return line 6.

[0053] Note that the same effect as in the third embodiment can be achieved by making the thickness of the nonmagnetic metal plate 300 equal to or greater than the skin depth of the material of the nonmagnetic metal plate 200. Also, in FIG. 11 , the nonmagnetic metal plate 300 is disposed on each of the second surface of the first core 8a, the first surface of the fourth core 8d, the second surface of the fifth core 8e, and the first surface of the second core 8b, but this configuration is not limiting. If the distance between the first core 8a and the fourth core 8d is greater than the thickness of the nonmagnetic metal plate 300, the nonmagnetic metal plate 300 may be disposed only on the surface near the bent portion of the common-mode current return line 6. For example, if the bent portion of the common-mode current return line 6 is closer to the first surface of the fourth core 8d than to the second surface of the first core 8a, the nonmagnetic metal plate 300 may be disposed only on the first surface of the fourth core 8d. Similarly, for example, if the bent portion of the common mode current return line 6 is closer to the second surface of the fifth core 8e than to the first surface of the second core 8b, the non-magnetic metal plate 300 may be placed only on the second surface of the fifth core 8e.

[0054] Fifth Embodiment Fig. 12 is a diagram illustrating the configuration of a magnetic core 83 included in a power conversion device 50 according to a fifth embodiment. In the magnetic core 83 shown in Fig. 12, the common mode current return line 6 shown in Fig. 10 is divided into two common mode current return lines 6a and 6b, which pass through the first core 8a and the second core 8b. One of the two divided lines, the common mode current return line 6a, is arranged parallel to the electrical wiring 5a. The other of the two divided lines, the common mode current return line 6b, is arranged parallel to the electrical wiring 5c. Note that "parallel" as used here does not necessarily mean "parallel" in the strict sense, but may mean that the lines are substantially parallel.

[0055] Next, the effect of the magnetic core 83 of the fifth embodiment will be described. In FIG. 12 , in-phase zero-phase currents, indicated by dashed arrows, flow through the electrical wirings 5a, 5b, and 5c. Meanwhile, in-phase currents, indicated by dashed arrows, flow through the common-mode current return lines 6a and 6b. These currents are in-phase and opposite in phase to the zero-phase currents flowing through the electrical wirings 5a, 5b, and 5c. Therefore, the magnetic flux, indicated by the solid line, generated by the current flowing through the electrical wiring 5a and the magnetic flux, indicated by the dashed line, generated by the current flowing through the common-mode current return line 6a are opposite in direction and cancel each other out. Similarly, the magnetic flux, indicated by the solid line, generated by the current flowing through the electrical wiring 5c ​​and the magnetic flux, indicated by the dashed line, generated by the current flowing through the common-mode current return line 6b are opposite in direction and cancel each other out. As a result, even when the electrical wiring 5a is bent and drawn out from the first core 8a and the second core 8b, the common mode current return lines 6a arranged parallel to the electrical wiring 5a suppress the generation of local magnetic flux, making it possible to prevent the magnetic flux from entering the magnetic core 83. Furthermore, even when the electrical wiring 5c ​​is bent and drawn out from the first core 8a and the second core 8b, the common mode current return lines 6b arranged parallel to the electrical wiring 5c ​​suppress the generation of local magnetic flux, making it possible to prevent the magnetic flux from entering the magnetic core 83.

[0056] Although the configuration of Fig. 12 does not include nonmagnetic metal plate 200, nonmagnetic metal plate 200 may be provided on the first surface of first core 8a and the second surface of second core 8b as shown in Fig. 10. In the fifth embodiment, the common-mode current return line 6a, which is one of the two divided lines, is arranged parallel to electrical wiring 5a, which is the first electrical wiring of three electrical wirings 5a, 5b, and 5c, and the other common-mode current return line 6b is arranged parallel to electrical wiring 5c, which is the second electrical wiring of three electrical wirings 5a, 5b, and 5c, as applied to the configuration of Fig. 10. However, this may also be applied to the configuration of Fig. 11 according to the fourth embodiment. When applied to the configuration of Fig. 11, the effects described in the fourth embodiment can also be obtained.

[0057] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or different embodiments may be combined with each other. It is also possible to omit or modify parts of the configurations as long as they do not deviate from the gist of the invention.

[0058] 2, 2A Input circuit section, 3 Filter capacitor, 4 Three-phase inverter, 4a Switching element, 5 Three-phase AC power line, 5a, 5b, 5c Electrical wiring, 6, 6a, 6b Common mode current return line, 7 Grounding line, 8, 81, 82, 83 Magnetic core, 8a First core, 8b Second core, 8c Third core, 8d Fourth core, 8e Fifth core, 10 Overhead line, 11 Current collector, 12 Rail, 13 Wheel, 15 Propulsion motor, 21 Main transformer, 22 Converter, 50 Power conversion device, 90, 92 Core member, 100, 110 Magnetic flux, 120 Local magnetic flux, 200, 300 Non-magnetic metal plate.

Claims

1. A power conversion device for a railway vehicle for driving a propulsion motor mounted on the railway vehicle, comprising: a three-phase inverter that converts DC power into AC power for the traction motor; a magnetic core through which a three-phase AC power line, which is an electrical wiring that connects the three-phase inverter and the propulsion motor, and a common mode current return line, which is an electrical wiring that connects between the ground potential of the power conversion device and the ground potential of the propulsion motor, pass; Equipped with The magnetic core is a first core disposed on the side of the three-phase inverter and through which both the three-phase AC power lines and the common mode current return line pass; a second core disposed on the side of the traction motor and through which both the three-phase AC power line and the common mode current return line pass; a third core disposed between the first core and the second core and through which only the three-phase AC power line passes; Equipped with In each of the first, second and third cores, a surface facing the three-phase inverter side is defined as a first surface, and a surface facing the traction motor side is defined as a second surface, At least one of the three electric wirings constituting the three-phase AC power line is drawn out from the second core to the second surface side so as not to be parallel to the other one or two electric wirings.

2. A power conversion device for a railway vehicle.

2. The first, second and third cores are formed in a square or circular ring shape, A non-magnetic metal plate is provided on the second surface of the second core.

2. The power conversion device for a railway vehicle according to claim 1.

3. A non-magnetic metal plate is provided on the first surface of the first core.

2. The power conversion device for a railway vehicle according to claim 1.

4. At least one of the three electric wirings constituting the three-phase AC power line is drawn out from the first core to the first surface side so as not to be parallel to the other one or two electric wirings.

4. The power conversion device for a railway vehicle according to claim 3.

5. a fourth core disposed between the first core and the third core and through which only the three-phase AC power line passes; a fifth core disposed between the second core and the third core, through which only the three-phase AC power line passes; Equipped with The fourth and fifth cores are formed in a square or circular ring shape, In each of the fourth and fifth cores, a surface facing the three-phase inverter is defined as a third surface, and a surface facing the traction motor is defined as a fourth surface. A non-magnetic metal plate is provided on each of the fourth surface of the first core, the third surface of the fourth core, the fourth surface of the fifth core, and the third surface of the second core.

3. The power conversion device for a railway vehicle according to claim 2.

6. The non-magnetic metal plate is formed to have a thickness equal to or greater than the skin depth.

3. The power conversion device for a railway vehicle according to claim 2.

7. The common mode current return line is divided into two and passes through the first and second cores.

7. The power conversion device for a railway vehicle according to claim 1.

8. one of the two divided common mode current return lines is arranged parallel to a first electrical wiring which is one of three electrical wirings constituting the three-phase AC power line; The other of the two divided common mode current return lines is arranged parallel to a second electrical wiring different from the first electrical wiring among the three electrical wirings constituting the three-phase AC power line.

8. The power conversion device for a railway vehicle according to claim 7.