JP2025007845A - Shielding systems and electrical equipment - Google Patents

Abstract

To reduce common mode noise while adopting a resin housing.SOLUTION: A shield system 10 has a battery 20, an MG 30, and an inverter 40. The inverter 40 has a resin housing 41, an electric part 42 accommodated in the housing 41, and a return conductor 43. The battery 20 has a metal housing 21. The MG 30 has a metal housing 31. The battery 20 and the inverter 40 are connected through a P line 51P and an N line 51N. The inverter 40 and the MG 30 are connected through an output line 61. The return conductor 43 is electrically connected to the housings 21 and 31, and provides a return path of common mode current.SELECTED DRAWING: Figure 1

Description

The disclosure in this specification relates to a shielding system and electrical equipment.

Patent document 1 discloses an electric unit. The contents of the prior art document are incorporated by reference as explanations of the technical elements in this specification.

JP 2017-216845 A

In Patent Document 1, multiple electrical devices, multiple bus bars, and a holder that holds the bus bars are housed in a metal case and arranged on one side of a metal frame. The holder holds a cooling bar together with the bus bars. The cooling bar is connected to the metal frame at multiple points that are spaced apart from each other. Because a common mode current flows through the cooling bar, the loop area is reduced, and common mode noise can be reduced.

In recent years, there has been a demand for the housings of electrical equipment to be made of resin in order to reduce weight, costs, and CO2 emissions during manufacturing. However, when a resin housing is used, the path of the common mode current is interrupted by the resin housing. In other words, the shielding structure of the shielding system is interrupted by the resin housing. In terms of the above and other aspects not mentioned, further improvements are required in shielding systems and electrical components.

One of the objectives of this disclosure is to provide a shielding system and electrical equipment that can reduce common mode noise while using a resin housing.

One aspect of the disclosure is a shield system comprising:
A first device (20, 30) having a metal member (21, 31);
A second device (40) having a resin housing (41) and an electric component (42) housed in the resin housing;
A power line (51, 61) connecting the first device and the second device;
Equipped with
The second device has a return conductor (43) electrically connected to the metallic member and providing a return path for the common mode current.

According to the disclosed shielding system, the second device has a resin housing and a return conductor. The return conductor is electrically connected to the metal member of the first device. The common mode current that flows from the second device through the power line to the first device returns to the second device through the metal member and the return conductor. In this way, the return conductor provides a return path for the common mode current. Therefore, it is possible to reduce common mode noise while employing a resin housing.

Another aspect of the disclosure is an electrical device, comprising:
A resin housing (41);
An electrical component (42) housed in a resin housing and electrically connected to other devices through a power line;
A return conductor (43) electrically connected to a metal member of another device to provide a return path for common mode noise;
Equipped with.

The disclosed electrical device includes a resin housing and a return conductor. The return conductor is electrically connected to a metal member of another device. A common mode current that flows from the electrical device to the other device through a power line returns to the electrical device through the metal member and the return conductor. In this way, the return conductor provides a return path for the common mode current. Therefore, it is possible to reduce common mode noise while still using a resin housing.

The various aspects disclosed in this specification employ different technical means to achieve their respective objectives. The claims and the reference characters in parentheses in this section are illustrative of the corresponding relationships with the embodiments described below, and are not intended to limit the technical scope. The objectives, features, and advantages disclosed in this specification will become clearer with reference to the detailed description that follows and the accompanying drawings.

1 illustrates an example of an electrical device and a shield system according to a first embodiment. FIG. 1 is a diagram showing a reference example of a shield system. FIG. 1 is a diagram showing a reference example of a shield system. FIG. 13 is a diagram showing the results of magnetic field measurement. FIG. 13 is a diagram showing the results of electric field measurement. FIG. 13 is a diagram showing another example of a shield system. FIG. 13 is a diagram showing another example of a shield system. FIG. 1 is a cross-sectional view showing an example of an electrical device. FIG. 4 is a plan view showing a return conductor. FIG. 11 is a plan view showing another example of a return conductor. FIG. 11 is a plan view showing another example of a return conductor. FIG. 4 is a cross-sectional view showing another example of a return conductor. FIG. 4 is a cross-sectional view showing another example of a return conductor. FIG. 4 is a cross-sectional view showing another example of a return conductor. FIG. 4 is a cross-sectional view showing another example of a return conductor. FIG. 4 is a cross-sectional view showing another example of a return conductor. FIG. 2 illustrates an example of an interface. FIG. 13 is a diagram showing another example of an interface. FIG. 13 is a diagram showing another example of an interface. FIG. 13 is a diagram illustrating another example of an interface. FIG. 11 is a diagram showing an example of electrical connection between a return conductor and an electrical component. FIG. 13 is a diagram showing an example of a configuration including a Y capacitor. A diagram showing the relationship between the inductance of the battery side portion of the return conductor and conducted noise. FIG. 13 is a diagram showing another example of a configuration including a Y capacitor. A diagram showing the relationship between the inductance of the MG side portion of the return conductor and conducted noise. FIG. 13 is a diagram illustrating an example of a shield system according to a second embodiment. FIG. 11 is a diagram showing the measurement results of conducted noise. FIG. 4 is a plan view showing the positional relationship between the bus bars and the return conductors. FIG. 4 is a side view showing the positional relationship between the bus bar and the return conductor. FIG. 11 is a diagram showing the relationship between the width of the return conductor, the facing distance, and the inductance. FIG. 13 is a diagram showing another example of a shield system. FIG. 11 is a diagram showing the measurement results of conducted noise.

Below, several embodiments will be described with reference to the drawings. Note that in each embodiment, corresponding components are given the same reference numerals, and duplicated descriptions may be omitted. When only a portion of the configuration is described in each embodiment, the configuration of the other embodiment described above can be applied to the other portions of the configuration. In addition to the combinations of configurations explicitly stated in the description of each embodiment, configurations of several embodiments can be partially combined together even if not explicitly stated, as long as there is no particular problem with the combination.

Note that the term "A and/or B" means at least one of A and B. In other words, it may include only A, only B, or both A and B.

First Embodiment
The shielding system according to the present embodiment is applicable to a configuration including a plurality of electrical devices and power lines connecting the electrical devices, with at least one electrical device having a plastic housing. The shielding system may be referred to as an electrical unit having a shield structure. The shielding system may be mounted on a moving object. The use of a plastic housing allows for weight reduction, cost reduction, and reduction in CO2 emissions during manufacturing.

The moving object may be, for example, a vehicle, an aircraft, a ship, construction machinery, or agricultural machinery. The shield system may include, as electrical equipment, a power converter such as an inverter or a DCDC converter, an MG, a battery, an ESU, a charger, a heater, an electric compressor, and the like. MG is an abbreviation for Motor Generator. ESU is an abbreviation for Electricity Supply Unit. The ESU is a device that integrates the functions of a current sensor that detects current, charging, power conversion, and power distribution. Instead of the MG, a rotating electric machine having only one of the functions of an electric motor or a generator may be included.

Below, an example is shown in which the shielding system is mounted on a vehicle. Such a shielding system is sometimes referred to as an on-board system. Also, an example is shown in which the shielding system includes a battery, an MG that functions as a driving source for the vehicle, and an inverter (power converter). Such a shielding system is sometimes referred to as an electric drive system.

<Basic configuration>
Fig. 1 shows an example of an electric device having a resin housing and a shielding system according to the present embodiment. In Fig. 1, for clarity, a metal housing is shown by a solid line and a resin housing is shown by a dashed line. As shown in Fig. 1, the shielding system 10 includes a battery (BAT) 20, an MG 30, and an inverter (INV) 40 as electric devices. In addition to the multiple electric devices, the shielding system 10 includes shielded wires 50 and 60 that provide power lines.

Battery 20 is a high-voltage DC power source composed of a rechargeable secondary battery such as a lithium-ion battery or a nickel-metal hydride battery. Battery 20 includes a housing 21 and a battery cell (electrical component) (not shown) housed in housing 21. Battery 20 includes at least one assembled battery composed of a plurality of battery cells. The number and arrangement of the plurality of battery cells are not particularly limited. The plurality of battery cells may be connected in series, or in parallel and in series. Each battery cell has a power generating element and a battery case that houses the power generating element. Battery 20 includes a bus bar that connects the electrode terminals of each battery cell.

The battery 20 includes a metal member electrically connected to the return conductor described below to provide a path for a common mode current. The battery 20 may include a metal housing 21 as a metal member, or may include other metal members, such as a bus bar or a metal battery case, instead of or in addition to the housing 21. The battery 20 may be electrically connected to the body ground as shown in FIG. 1, or may be unconnected to the body ground. The body ground is a reference potential in the vehicle, and is provided by, for example, the frame (chassis) of the vehicle. For example, the metal housing 21 may be electrically connected to the frame. The metal housing 21 provides a reference potential in the battery 20. The reference potential in the battery 20 may be referred to as a case ground, a power supply ground, or the like. In FIG. 1, the body ground is indicated as body GND.

MG30 is a three-phase AC rotating electric machine. MG30 functions as a driving source for the vehicle, i.e., an electric motor. MG30 functions as a generator during regeneration. MG30 includes a housing 31 and rotating electric machine elements (electrical components) such as a winding 32 housed in the housing 31.

Like the battery 20, the MG 30 also has a metal member electrically connected to the return conductor to provide a path for the common mode current. The MG 30 may have a metal housing 31 as the metal member, or may have another metal member instead of or in addition to the housing 31. The MG 31 may be electrically connected to the body ground, or may be unconnected to the body ground. For example, the metal housing 31 may be electrically connected to the frame. The metal housing 31 provides a reference potential for the MG 30.

The inverter 40 performs power conversion between the battery 20, which is a DC power source, and the MG 30. The inverter 40 is a DC-AC conversion circuit. The inverter 40 converts DC voltage into three-phase AC voltage according to switching control by a circuit not shown, and outputs it to the MG 30. This causes the MG 30 to drive so as to generate a predetermined torque. During regenerative braking of the vehicle, the inverter 40 converts the three-phase AC voltage generated by the MG 30 in response to rotational force from the wheels into DC voltage according to switching control by the above circuit, and outputs it to the battery 20. In this way, the inverter 40 performs bidirectional power conversion between the battery 20 and the MG 30.

The inverter 40 is configured with upper and lower arm circuits for three phases. Each arm is configured with a switching element such as a MOSFET or an IGBT. MOSFET is an abbreviation for Metal Oxide Semiconductor Field Effect Transistor. IGBT is an abbreviation for Insulated Gate Bipolar Transistor. In addition to the upper and lower arm circuits for three phases, the inverter 40 may also be equipped with a smoothing capacitor.

The inverter 40 includes a resin housing 41 and electrical components 42 housed in the housing 41. The electrical components 42 are, for example, the switching elements and capacitor elements described above. The inverter 40 further includes a return conductor 43. The return conductor 43 is electrically connected to a metal component of another electrical device and provides a path for the common mode current, specifically, a return path. The inverter 40 may be electrically connected to the body ground or may be unconnected to the body ground.

The shielded wires 50 and 60 have a known structure. Each of the shielded wires 50 and 60 includes an internal conductor, an insulating material surrounding the internal conductor, an external conductor arranged to surround the internal conductor via the insulating material, and an insulating coating covering the external conductor. The shielded wire 50 includes an internal conductor 51, which is a P line 51P and an N line 51N, and an external conductor 52. The P line 51P electrically connects the positive terminal of the battery 20 to the high potential side terminal of the upper and lower arm circuits of the inverter 40. The N line 51N electrically connects the negative terminal of the battery 20 to the low potential side terminal of the upper and lower arm circuits of the inverter 40. The internal conductor 51, that is, the P line 51P and the N line 51N, are power lines connecting the battery 20 and the inverter 40. The P line 51P and the N line 51N are arranged opposite each other with an insulating material interposed therebetween. The P line 51P and the N line 51N run parallel to each other.

The external conductor 52 functions as an electromagnetic shield for the P line 51P and the N line 51N, and is therefore sometimes referred to as a PN shield wire. As described above, the external conductor 52 is disposed near the internal conductor 51. The external conductor 52 is disposed opposite the internal conductor 51 with an insulating material interposed between them. The external conductor 52 runs parallel to the internal conductor 51. One of the ends of the external conductor 52 is electrically connected to a metal member of the battery 20, for example, the metal housing 21. The other end of the external conductor 52 is electrically connected to the return conductor 43.

The shielded wire 60 has an output line 61, which is an internal conductor, and an external conductor 62. Hereinafter, the output line 61 may be referred to as the internal conductor 61. The output line 61 electrically connects the output terminals (midpoints) of the upper and lower arm circuits of the inverter 40 to the windings 32 of the corresponding phases of the MG 30. The output line 61 includes a U-phase output line, a V-phase output line, and a W-phase output line. The output line 61 is a power line that connects the inverter 40 and the MG 30.

The external conductor 62 functions as an electromagnetic shield for the output line 61, and is therefore sometimes referred to as an MG shield line, a motor shield line, etc. As described above, the external conductor 62 is disposed near the output line 61. The external conductor 62 is disposed opposite the output line 61 with an insulating material interposed between them. One of the ends of the external conductor 62 is electrically connected to the return conductor 43. The other end of the external conductor 62 is electrically connected to a metal member of the MG 30, for example, the metal housing 31.

In the above configuration, the battery 20 and the MG 30 correspond to the first device. The inverter 40 corresponds to the second device. The inverter 40 corresponds to an electrical device having a plastic housing.

Figures 2 and 3 are diagrams showing a reference example of a shielding system. Figures 2 and 3 correspond to Figure 1. In the reference example, elements related to this embodiment are indicated by adding an r to the end of their reference numerals.

In the reference example shown in FIG. 2, the inverter 40r has a metal housing 41r. The inverter 40r does not have a return conductor. The outer conductor 52r of the shielded wire 50r is electrically connected to the housing 41r. The outer conductor 62r of the shielded wire 60r is also electrically connected to the housing 41r. The other configurations are the same as those shown in FIG. 1.

In the reference example shown in FIG. 3, the inverter 40r has a resin housing 41r. The inverter 40r does not have a return conductor. Therefore, the outer conductor 52r of the shielded wire 50r is not electrically connected to the elements of the inverter 40r. The outer conductor 62r of the shielded wire 60r is also not electrically connected to the elements of the inverter 40r. The other configurations are the same as those shown in FIG. 1.

1, 2, and 3, the flow of the common mode current is indicated by dashed arrows. In the reference example shown in FIG. 2, a metal housing 41r is used as described above. Therefore, the housing 41r provides a path for the common mode current, specifically a return path. The common mode current generated by the switching operation flows from the inverter 40r through the P line 51Pr and the N line 51Nr to the battery 20r, and is transmitted to the external conductor 52r through the metal members of the battery 20r. It then flows from the external conductor 52r through the housing 41r and the external conductor 62r to the MG 30r, and returns to the inverter 40r through the output line 61r.

The magnitude of electromagnetic noise is proportional to the magnitude of the flowing current and the loop area, and inversely proportional to the cube of the antenna distance. In the configuration shown in FIG. 2, the metal housing 41r is provided, so the return line is close to the power line. This makes the loop area of the common mode current small. This makes it possible to reduce radiated noise (common mode noise).

In the reference example shown in FIG. 3, a resin housing 41r is used as described above. Therefore, the common mode current flows from the inverter 40r through the P line 51Pr and the N line 51Nr to the battery 20r, and is transmitted from the battery 20r to the MG 30r through the body ground. Then, it returns to the inverter 40r through the output line 61r. In the configuration shown in FIG. 3, the shield structure is divided between the inverter 40r and the external conductors 52r and 62r, so the return line is located away from the power line. This makes the loop area of the common mode current large. Therefore, the radiation noise (common mode noise) is larger than in the configuration shown in FIG. 2. In other words, there is a risk of noise leakage.

In the configuration of this embodiment shown in FIG. 1, the return conductor 43 provides a path for the common mode current, specifically a return path, instead of the resin housing 41. The common mode current flows from the inverter 40 through the P line 51P and the N line 51N to the battery 20, and is transmitted to the external conductor 52 through the metal members of the battery 20. Furthermore, the common mode current flows from the external conductor 52 through the return conductor 43 and the external conductor 62 to the MG 30, and returns to the inverter 40 through the output line 61. In the configuration shown in FIG. 1, the return conductor 43 is provided, so that the return line is close to the power line. This makes the loop area of the common mode current small. The loop area is equal to or less than that of the reference example shown in FIG. 2. Therefore, the radiation noise (common mode noise) can be reduced.

Figure 4 shows the results of measuring the magnetic field. In the figure, the metal casing corresponds to the configuration of the reference example in Figure 2, the plastic casing corresponds to the configuration of the reference example in Figure 3, and the return conductor corresponds to the configuration in Figure 1. The metal casing and the return conductor gave almost the same results. By adding a return conductor to the plastic casing, a noise reduction of 40 dB was confirmed at, for example, 1 MHz. Figure 5 shows the results of measuring the electric field. By adding a return conductor to the plastic casing, a reduction in strength of 38 dB was confirmed at, for example, 1 MHz. Thus, the effects of the return conductor 43 could be confirmed from the results of measuring the magnetic field and electric field.

The shielding system 10 is not limited to the configuration shown in FIG. 1. FIG. 1 shows an example in which the metal members of the battery 20 and the MG 30 are electrically connected to the return conductor 43 via the outer conductors 52, 62 of the shielded wires 50, 60, but is not limited to this. In other words, it is not limited to the example in which the shielded wires 50, 60 are used. For example, as shown in FIG. 6, the return conductor 43 may be electrically connected to the metal member of the battery 20 using a connection wire 53 provided separately from the P wire 51P and the N wire 51N. The return conductor 43 may be electrically connected to the metal member of the MG 30 using a connection wire 63 provided separately from the output wire 61.

Although not shown in the figure, the return conductor 43 may be extended and electrically connected to the metal components of the battery 20 and the MG 30 without going through the external conductors 52, 62 or the connecting wires 53, 63. In other words, they may be directly connected.

The electric device having a return conductor is not limited to the inverter 40 in the above shielding system 10. Instead of the inverter 40, the return conductor may be provided in the battery 20 or the MG 30. The return conductor may be provided in at least one of the battery 20, the MG 30, and the inverter 40. For example, as shown in FIG. 7, the battery 20 may have a resin case 21 and a return conductor 23. In FIG. 7, the battery 20 and the inverter 40 have return conductors 23 and 43. The common mode current flows from the P line 51P and the N line 51N to the external conductor 52 through the return conductor 23. The battery 20, the MG 30, and the inverter 40 may all have a return conductor. A part of the battery 20, the MG 30, and the inverter 40 corresponds to the first device, and the other part corresponds to the second device. The return conductor of the first device corresponds to the metal member.

<Return conductors and electrical equipment>
The material, arrangement, shape, etc. of the return conductor 43 are not particularly limited as long as it can be electrically connected to a metal member of another electric device. The return conductor 43 may be formed using a material having excellent electrical conductivity, such as a metal material such as copper, aluminum, or iron. A material having excellent electrical conductivity other than metal may also be used.

Figures 8 and 9 show an example of a return conductor 43 and an inverter 40 (electrical equipment) equipped with the return conductor 43. In Figures 8 and 9, the height direction of the inverter 40 is the Z direction, one direction perpendicular to the Z direction is the X direction, and the direction perpendicular to both the Z direction and the X direction is the Y direction. For convenience, members that electrically connect electrical components to each other, such as bus bars, are omitted in Figure 8.

As shown in FIG. 8, the inverter 40 has electrical components 42 housed in a resin housing 41, such as a semiconductor module 421, an output terminal block 422, a capacitor element 423 that provides a smoothing capacitor, an input terminal block 424, and a circuit board 425. The semiconductor module 421 provides upper and lower arm circuits. The output terminal of the semiconductor module is electrically connected to an output bus bar 426 via the output terminal block 422. The inverter 40 has output bus bars 426 for three phases. The output bus bars 426 protrude outside the housing 41. An output line 61 is connected to the protruding portion of the output bus bar 426.

The high potential side terminal and low potential side terminal of the semiconductor module 421 are connected to the corresponding terminals of the capacitor element 423 via conductive members such as bus bars. The terminals of the capacitor element 423 are connected to a P bus bar 427 and an N bus bar (not shown) via an input terminal block 424. The P bus bar 427 and the N bus bar protrude outside the housing 41. A P line 51P is connected to the protruding portion of the P bus bar 427. Similarly, an N line 51N is connected to the protruding portion of the N bus bar. The circuit board 425 has circuits formed thereon for driving the switching elements provided in the semiconductor module 421.

At least a portion of the return conductor 43 may be housed in a resin housing 41. In the example shown in FIG. 8, a portion of the return conductor 43 is disposed in the space within the housing 41, and another portion protrudes outside the housing 41. As shown in FIGS. 8 and 9, the return conductor 43 has a main body portion 431 disposed within the housing 41, and a terminal portion 432 connected to the main body portion 431 and extending from an end of the main body portion 431.

The return conductor 43 is, for example, a metal plate whose thickness direction is in the Z direction. The return conductor 43 is fixed to the housing 41 by screw fastening or the like. The main body 431 has a generally rectangular shape in plan with the X direction as the longitudinal direction and the Y direction as the transverse direction. The main body 431 is arranged so as to overlap electrical components such as the semiconductor module 421 and the capacitor element 423 when viewed in plan in the Z direction. The main body 431 divides the space within the housing 41 into a space in which the semiconductor module 421, the capacitor element 423, etc. are arranged, and a space in which the circuit board 425 is arranged. In other words, it divides the space between the power circuit element and the drive circuit element that drives the power circuit. The main body 431 provides a shielding function between the power circuit element and the drive circuit element.

The return conductor 43 having such a body portion 431 is sometimes referred to as a metal stay or the like. A through hole (not shown) is formed in the body portion 431. For example, a signal terminal (not shown) of the semiconductor module 421 is inserted through the through hole and connected to the circuit board 425. At least one of the electrical components 42 may be fixed to the body portion 431.

The terminal portions 432 extend in the X direction from the ends of the main body portion 431 in the X direction. At least a portion of the terminal portion 432 protrudes outside the housing 41. The outer conductor 52 of the shielded wire 50 is connected to one of the terminal portions 432, and the outer conductor 62 of the shielded wire 60 is connected to the other terminal portion 432. The return conductor 43 is surface-connected to the outer conductors 52 and 62. The return conductor 43 and the outer conductors 52 and 62 are connected such that their plate surfaces overlap. A portion of the return conductor 43 faces the inner conductor 51 and/or the P bus bar 427 and the N bus bar in the Z direction. A portion of the return conductor 43 faces the inner conductor 61 and/or the output bus bar 426 in the Z direction.

The shape and arrangement of the return conductor 43 housed in the housing 41 are not limited to the above example. For example, as shown in FIG. 10, a linear return conductor 43 may be used. The return conductor 43 may be a thin metal wire. The return conductor 43 may include only one thin metal wire, or may include multiple thin metal wires as shown in FIG. 10. One end of each thin metal wire is connected to the outer conductor 52, and the other end is connected to the outer conductor 62. The return conductor 43 is wire-connected to the outer conductors 52 and 62. The above-mentioned surface connection can reduce inductance more than a line connection. Surface connection is more effective at reducing common-mode noise.

As shown in FIG. 11, a return conductor 43 may be used in which the main body 431 is in a mesh shape. The return conductor 43 is not limited to being flat. It may have a bent portion, and the thickness may vary in parts.

Although an example has been shown in which a metal stay placed inside the housing 41 is used as the return conductor 43, this is not limiting. Another metal member placed inside the housing 41 may also be used. For example, in a configuration that incorporates a cooler, the metal base that constitutes the cooler may also be used.

As shown in FIG. 12, the return conductor 43 may be inserted into the housing 41. That is, a portion of the return conductor 43 may be embedded in the plastic housing 41. The return conductor 43 may be molded integrally with the housing 41. FIG. 12 corresponds to FIG. 10. The return conductor 43 has an embedded portion 433 embedded in the housing 41, and a terminal portion 434 connected to the embedded portion 433 and protruding outward from the housing 41.

As shown in FIG. 13, the return conductor 43 may be disposed on the outer surface 41a of the housing 41. FIG. 13 corresponds to FIG. 10. The return conductor 43 is provided on the outer surface 41a by plating or the like. Since the return conductor 43 is located outside the housing 41, it is not necessary to provide a terminal portion for connection to the power line. Of course, a terminal portion may be provided.

As shown in FIG. 14, the return conductor 43 may be disposed on the inner surface 41b of the housing 41. FIG. 14 corresponds to FIG. 10. The return conductor 43 is provided on the inner surface 41b by plating or the like. The return conductor 43 has a main body portion 435 disposed on the inner surface 41b, and a terminal portion 436 connected to the main body portion 435 and protruding outward from the housing 41.

As shown in FIG. 15, the inverter 40 may include multiple return conductors 43. The multiple return conductors 43 may be of different types, for example, a combination of a metal stay and an external arrangement, or may be of the same type. In FIG. 15, the return conductor 43 covers the semiconductor module 421 and the capacitor element 423 from above and below in the Z direction. Although not shown, the return conductor 43 may be provided so as to surround the semiconductor module 421 and the capacitor element 423. For example, the return conductor 43 may be provided so as to cover the semiconductor module 421 and the capacitor element 423 not only in the Z direction but also in the Y direction. By reducing the inductance of the path through which the common mode current flows, the effect of reducing common mode noise can be improved.

As shown in FIG. 16, the ground layer 425G of the circuit board 425 may be used as the return conductor 43. The ground layer 425G provides the main body 431 of the return conductor 43. A terminal portion 432 is joined to the ground layer 425G. The ground layer 425G is a so-called solid ground. As shown in FIG. 16, the ground layer 425G may be provided over almost the entire back surface of the circuit board 425.

<Input/output interface>
In an electric device having a return conductor, the position of an input/output interface for electrically connecting to another electric device is not particularly limited. In an inverter 40 having a return conductor 43, an interface with the battery 20 and an interface with the MG 30 may be provided on different sides of the housing 41.

For example, as shown in FIG. 17, the housing 41 has a first surface 41c and a second surface 41d. The second surface 41d is the surface opposite the first surface 41c in one direction. The return conductor 43 extends in one direction, that is, in the opposing direction of the first surface 41c and the second surface 41d. The inverter 40 may have an interface portion on the first surface 41c and the second surface 41d. The inverter 40 shown in FIG. 1, FIG. 8, etc. corresponds to the configuration shown in FIG. 17.

In the example shown in FIG. 18, the second surface 41d is located next to the first surface 41c. The return conductor 43 extends from the first surface 41c toward the second surface 41d. The return conductor 43 may have, for example, a bent portion. The inverter 40 has interface portions on the first surface 41c and the second surface 41d.

In the inverter 40, the interface with the battery 20 and the interface with the MG 30 may be provided on a common surface of the housing 41. In the example shown in FIG. 19, the inverter 40 has two interface parts on the first surface 41c.

As shown in FIG. 20, the inverter 40 may have only one interface unit. The inverter 40 has one interface unit on the first surface 41c. The battery 20 shown in FIG. 8 corresponds to the configuration shown in FIG. 20.

In a configuration having only one interface unit, the common mode current may return to the electrical component 42 from the return conductor 43 via the parasitic capacitance 70, as shown by the dashed arrow in FIG. 21. The parasitic capacitance 70 may be formed, for example, between the bus bar connected to the output terminal of the upper and lower arm circuits and the return conductor 43. A capacitor may be provided instead of the parasitic capacitance 70.

In each of Figures 17 to 20, an example of an inverter 40 is shown, but this is not limited to this. It can be applied to any electrical device that has a plastic housing and a return conductor.

<Y capacitor>
The shielding system 10 may include a Y capacitor. One terminal of the Y capacitor is connected to the power line, and the other terminal is connected to the return conductor. For example, in the above-described shielding system 10, a Y capacitor 80 may be provided as shown in Fig. 22. Fig. 22 shows the periphery of the inverter 40 in the shielding system 10.

One of the Y capacitors 80 is provided between the P line 51P and the return conductor 43. The other Y capacitor 80 is provided between the N line 51N and the return conductor 43. A passive element such as a resistor may be connected in series to the Y capacitor 80 (capacitor element) or in parallel. Depending on the voltage of the battery 20, the Y capacitor 80 may be provided only between the P line 51P and the return conductor 43, or only between the N line 51N and the return conductor 43. By providing the Y capacitor 80, a path of common mode current including the Y capacitor 80 is formed, as shown by the dashed arrow. The loop area of this path is smaller than the loop area of a path that does not pass through the Y capacitor 80.

As shown in FIG. 22, the Y capacitor 80 may be connected to the return conductor 43 at a position close to the end of the return conductor 43 on the battery 20 side. In FIG. 22, the Y capacitor 80 is connected to the return conductor 43 at a position close to the connection end with the external conductor 52, between the connection end with the external conductor 52 and the connection end with the external conductor 62. This makes it possible to reduce the inductance of the portion of the return conductor 43 closer to the battery 20 than the Y capacitor 80, compared to a configuration in which the Y capacitor 80 is connected to the middle position between the two connection ends or close to the connection end with the external conductor 62.

In the following, the portion of the return conductor 43 closer to the battery 20 than the connection with the Y capacitor 80 may be referred to as the portion of the return conductor 43 on the battery 20 side. The portion of the return conductor 43 closer to the MG 30 than the connection with the Y capacitor 80 may be referred to as the portion of the return conductor 43 on the MG 30 side.

Figure 23 shows the relationship between the inductance of the part of the return conductor 43 on the battery 20 side and the conducted noise. The conducted noise, shown on the vertical axis, increases in intensity the further up in the figure. Three levels of inductance are shown, with the solid line showing the smallest inductance and the dashed line showing the largest inductance. The dashed line showing the inductance is a value between the solid line and the dashed line. As shown in Figure 23, it was confirmed that the smaller the inductance of the part of the return conductor 43 on the battery 20 side, the greater the effect of reducing common mode noise at frequencies below 1 MHz.

As shown in FIG. 24, the Y capacitor 80 may be connected to the return conductor 43 at a position close to the end of the return conductor 43 on the MG 30 side. In FIG. 24, the Y capacitor 80 is connected to the return conductor 43 at a position close to the connection end with the external conductor 62, between the connection end with the external conductor 52 and the connection end with the external conductor 62. This makes it possible to reduce the inductance of the MG 30 side portion of the return conductor 43 compared to a configuration in which the Y capacitor 80 is connected to the middle position between the two connection ends or close to the connection end with the external conductor 52.

Figure 25 shows the relationship between the inductance of the MG 30 side of the return conductor 43 and the conducted noise. As in Figure 23, the conducted noise shown on the vertical axis increases in intensity the further up the figure. Three levels of inductance are shown, with the solid line showing the smallest inductance and the dashed line showing the largest inductance. The dashed line showing the inductance is a value between the solid line and the dashed line. It was confirmed that in the wide frequency range of 0.1 MHz to over 10 MHz shown in Figure 25, the smaller the inductance of the MG 30 side of the return conductor 43 is, the greater the effect of reducing common mode noise.

Summary of the First Embodiment
According to this embodiment, the inverter 40 (second device, electric device) has a resin housing 41 and a return conductor 43. The return conductor 43 is electrically connected to the metal members of the battery 20 and the MG 30 (first device, other device). The common mode current flowing from the inverter 40 to the battery 20 through the power line returns to the inverter 40 through the metal members and the return conductor 43. In this way, the return conductor 43 provides a return path for the common mode current. The loop area of the path of the common mode current passing through the return conductor 43 is smaller than the loop area of the path of the common mode current passing through the body ground. Therefore, it is possible to reduce common mode noise while employing the resin housing 41. The shielding system 10 only needs to include at least one first device and at least one second device.

The power line may be the internal conductor 51, 61 of the shielded wire 50, 60, and the return conductor 43 may be electrically connected to the metal member via the external conductor 52, 62 of the shielded wire 50, 60. The external conductor 52, 62 of the shielded wire 50, 60 is used to connect the return conductor 43 to the metal member. The external conductor 52, 62 is disposed opposite the internal conductor 51, 61. In other words, the external conductor 52, 62 runs parallel to the internal conductor 51, 61 in the vicinity of the internal conductor 51, 61. This makes it possible to further reduce the loop area of the path of the common mode current.

In this way, by running the member connecting the return conductor 43 and the metal member parallel to the power line, that is, along the power line, the inductance (parasitic inductance) of the connecting member can be reduced by utilizing mutual inductance. This makes it easier for common mode current to flow through the path of the return conductor 43, reducing common mode noise.

In addition, in a configuration in which the internal conductor 51 includes a P line 51P and an N line 51N, the P line 51P and the N line 51N are arranged opposite each other, which effectively reduces normal mode noise.

The arrangement of the return conductor 43 is not particularly limited. At least a part of the return conductor 43 may be housed in the housing 41. The return conductor 43 may be inserted into the housing 41. At least a part of the return conductor 43 may be disposed on the outer surface of the housing 41. By using the return conductor 43 housed in the housing 41 or the return conductor 43 inserted into the housing 41, the loop area can be further reduced. In particular, by using the return conductor 43 housed in the housing 41, the effect of reducing the loop area is high. In addition, by using a metal member housed in the housing 41 as the return conductor 43, the configuration can be simplified.

The metal member of the first device (other device) is not particularly limited. It is sufficient if it provides a path for the common mode current. Metal housings 21 and 31 may be used as the metal member. Housings 21 and 31 provide a reference potential and case ground for each device, and provide a path for the common mode current.

The second device may be an inverter 40 (power converter). The inverter 40, which is equipped with a switching element, has a resin housing 41 and a return conductor 43. Therefore, the common mode current generated by switching can be passed through a path that utilizes the return conductor 43.

In the inverter 40, the return conductor 43 housed in the housing 41 may be disposed between an electrical component such as a semiconductor module 421 and a circuit board 425 electrically connected to the electrical component. In the inverter 40, the configuration can be simplified by using a metal member (metal stay) disposed between the electrical component and the circuit board as the return conductor 43.

The shielding system 10 may include a Y capacitor 80. One of the terminals of the Y capacitor 80 is connected to the power line (P line 51P, N line 51N), and the other terminal is connected to the return conductor 43. This forms a path for a common mode current that passes through the Y capacitor 80. Because the loop area of the path that passes through the Y capacitor 80 is small, common mode noise can be further reduced.

In a configuration including a Y capacitor 80, the first device may include a battery 20 and an MG 30 (rotating electric machine), and the second device may include an inverter 40. By applying the shielding system 10 to the electric drive system, common mode noise generated in the electric drive system can be reduced.

The Y capacitor 80 may be connected to the return conductor 43 at a position closer to the end of the return conductor 43 on the battery 20 side than the end of the return conductor 43 on the MG 30 side. The inductance of the part of the return conductor 43 on the battery 20 side can be made smaller than the connection part of the Y capacitor 80. This makes it possible to reduce common mode noise below 1 MHz.

The Y capacitor 80 may be connected to the return conductor 43 at a position closer to the MG 30 end of the return conductor 43, either on the battery 20 side or on the MG 30 side. The inductance of the return conductor 43 on the MG 30 side can be made smaller than the connection part of the Y capacitor 80. This makes it possible to reduce common mode noise over a wide frequency range.

Second Embodiment
This embodiment is a modification based on the previous embodiment, and the description of the previous embodiment can be used. In the previous embodiment, the resonance frequency between the capacitance of the Y capacitor and the inductance of the return path is not specifically mentioned. Instead, the above-mentioned resonance frequency may be in a predetermined frequency band.

26 is an equivalent circuit diagram of the shielding system 10 according to the present embodiment. FIG. 26 corresponds to the configuration shown in FIG. 1 and FIG. 22. For convenience, the housing 41 of the inverter 40 and the winding 32 of the MG 30 are omitted in FIG. 26. In FIG. 26, the parasitic inductance of each line is shown. The solid arrow, dashed arrow, and dashed arrow in FIG. 26 indicate the flow of the common mode current, that is, the path. The dashed arrow indicates the path (first return path) returning from the battery 20 to the semiconductor element 4211, and the dashed arrow indicates the path (second return path) returning from the battery 20 to the semiconductor element 4211 via the body ground. In FIG. 26, the U-phase output line 61U, the V-phase output line 61V, and the W-phase output line 61W are clearly shown as the output lines 61.

The shielding system 10 is an electric drive system, similar to the previous embodiment. The shielding system 10 includes a battery 20, an MG 30, and an inverter 40 (power converter). The battery 20 includes a metal member that provides a reference potential at the battery 20. The metal member is, for example, a metal housing 21. The metal member is electrically connected to the body ground. The MG 30 includes a metal member that provides a reference potential at the MG 30. The metal member is, for example, a metal housing 31. The metal member is electrically connected to the body ground.

The inverter 40 includes a resin housing 41 (not shown). The inverter 40 includes the above-mentioned semiconductor module 421 as an electrical component 42 housed in the housing 41. The semiconductor module 421 includes a semiconductor element 4211 in which a switching element is formed on a semiconductor substrate. The inverter 40 includes a return conductor 43. The return conductor 43 is electrically connected to the body ground via a ground line 45. The return conductor 43 is electrically connected to the metal member of the battery 20 via a connection line 53. The return conductor 43 is electrically connected to the metal member of the MG 30 via a connection line 63. Note that, instead of the connection lines 53 and 63, the external conductors 52 and 62 may be used. The external conductor 52 and the connection line 53 correspond to the first connection line, and the external conductor 62 and the connection line 63 correspond to the second connection line.

The return conductor 43 includes a PN return section 437, an MG return section 438, and a remaining section 439. The PN return section 437 is the section of the return conductor 43 from the connection with the connection line 53 to the connection with the Y capacitor 80. The MG return section 438 is the section of the return conductor 43 from the connection with the connection line 63 to the connection with the ground line 45. The remaining section 439 is the portion of the return conductor 43 excluding the PN return section 437 and the MG return section 438.

For example, in a metal stay, the main body 431 may provide at least a portion of the remaining portion 439, one of the terminal portions 432 may provide at least a portion of the PN return portion 437, and another of the terminal portions 432 may provide at least a portion of the MG return portion 438. A configuration without the remaining portion 439 may also be used.

One of the Y capacitors 80 is placed between the P line 51P, which is a power line, and the return conductor 43. The other Y capacitor 80 is placed between the N line 51N, which is a power line, and the return conductor 43.

The common mode current flows from the inverter 40 (semiconductor element 4211) to the battery 20 through the power lines P line 51P and N line 51N. The paths returning from the battery 20 to the semiconductor element 4211 include a first return path (first path) and a second return path (path). The first return path indicated by the dashed arrow is a path via the return conductor 43 and the Y capacitor 80. In the first return path, the common mode current flows from the metal member of the battery 20 to the semiconductor element 4211 through the connection line 53, the PN return section 437, and the Y capacitor 80.

The second return path indicated by the dashed-dotted arrow is a path via the body ground. In one of the second return paths, the common mode current flows from the metal component of the battery 20 to the semiconductor element 4211 through the body ground and ground line 45. In the other of the second return paths, the common mode current flows from the metal component of the battery 20 to the semiconductor element 4211 through the body ground, the metal component of the MG 30, the connection line 63, and the MG return section 438.

Figure 27 shows the measurement results of the conducted noise. The dashed line in Figure 27 shows the results of a reference example. In the reference example, the inverter has a plastic housing but does not have a return conductor. In this case, the common mode current returns from the battery 20 to the semiconductor element 4211 via the body ground, MG 30, and output line 61. Because the loop area is large, the level of common mode noise is high, as shown in Figure 27.

The dashed line in FIG. 27 shows the results when the inductance of the first return path, the inductance of the second return path via the ground line 45, and the inductance of the second return path via the connection line 63 are all set to the same value (10 nH). This configuration can reduce common mode noise compared to the configuration shown by the dashed line. However, it is difficult to reduce the noise level below the predetermined threshold value Th shown by the two-dot dashed line, especially in the low frequency range of the AM band (around 500 kHz).

Therefore, in the above-mentioned configuration, it is preferable to set L and C so that the resonance frequency of the inductance of the connection line 53 and the PN return section 437 and the capacitance of the Y capacitor 80 is in the AM band (530 kHz to 1.8 MHz). In particular, it is preferable to set the resonance frequency in the low frequency range (around 500 kHz) where noise reduction is difficult. The impedance Zpn(f) of the first return path can be expressed by the formula (1).
Zpn(f)=ω(Lpns+Lpnr)-1/(ωCy)...(1)

In formula (1), ω = 2πf, f is the frequency, Lpns is the parasitic inductance of the connection line 53, Lpnr is the parasitic inductance of the PN return section 437, and Cy is the capacitance of the Y capacitor 80. The impedance Zpn(f) has a minimum value at the resonance frequency. As a result, the impedance Zpn(f) becomes smaller than the impedance Zmg(f) of the second return path, and the common mode current flowing through the first return path increases. Therefore, as shown by the solid line in Figure 27, the noise level can be made lower than a predetermined threshold value Th in the low frequency range of the AM band (around 500 kHz). As a result, the noise level can be made lower than the threshold value Th throughout the entire AM band.

In the example shown by the solid lines in FIG. 27, the inductance of the first return path is 10 nH, the inductance of the second return path via the ground line 45 is 80 nH, and the inductance of the second return path via the connection line 63 is 80 nH. For example, the cross-sectional area of the ground line 45 and the MG return part 438 may be smaller than that of the PN return part 437. The PN return part 437 may be flat, and the ground line 45 and the MG return part 438 may be linear.

28 and 29, the inverter 40 includes a P bus bar 427 and an N bus bar 428. FIG. 28 is an enlarged plan view of the inverter 40 around the bus bar 427. FIG. 29 is a side view. A fastening hole 427a for connecting the P line 51P is provided near the end of the P bus bar 427. A fastening hole 428a for connecting the N line 51N is provided near the end of the N bus bar 428. As shown in FIG. 28 and 29, the PN return portion 437 of the return conductor 43 may be provided by the terminal portion 432 described above.

The PN return portion 437 may be arranged to overlap at least a portion of each of the P bus bar 427 and the N bus bar 428 in a plan view in the Z direction. In the example shown in FIG. 28, the PN return portion 437 is arranged to enclose the P bus bar 427 and the N bus bar 428. The PN return portion 437 has a width W. The PN return portion 437 may be arranged so that the plate surfaces of the P bus bar 427 and the N bus bar 428 face each other. In this configuration, the PN return portion 437 faces each of the P bus bar 427 and the N bus bar 428 at a predetermined distance d. The distance d is the distance between the opposing portions.

Figure 30 shows the relationship between width W, distance d, and inductance. Figure 30 shows the results of a simulation. In this case, the length in the X direction was set to 70 mm. Distance d = 10 mm is shown by a dashed line, distance d = 5 mm by a dashed line, and distance d = 1 mm by a solid line. The longer the width W, the smaller the inductance can be. However, the longer the width W, the smaller the effect of reducing inductance. The shorter the distance d, the smaller the inductance can be.

As described above, if the LC resonant frequency is set in the AM band and the impedance Zpn(f) in the AM band is made smaller than the impedance Zmg(f), the noise in the FM band (76.1 MHz to 94.9 MHz) will worsen as shown in FIG. 27. Therefore, as shown in FIG. 31, the capacitor 90 may be connected in parallel to the ground line 45. FIG. 31 shows another example of the shield system 10 (electric drive system). As shown in FIG. 31, the capacitor 90 may be connected in parallel to the ground line 45. The capacitor 90 may be connected in parallel to the MG return section 438. The capacitor 90 may be provided for at least one of the ground line 45 and the MG return section 438. For example, the capacitor 90 may be provided only on the ground line 45 or only on the MG return section 438. In high frequency ranges such as the FM band, the capacitor 90 becomes the main current path. This reduces the impedance.

Figure 32 shows the measurement results of the conducted noise. The dashed line in Figure 32 shows the measurement results of a configuration similar to the dashed line in Figure 27. The solid line shows the measurement results of a configuration in which a capacitor 90 is connected in parallel to each of the ground line 45 and the MG return section 438. As shown in Figure 32, the noise level in the FM band is reduced by adding the capacitor 90.

<Summary of the second embodiment>
As described above, the resonant frequency of the inductance of the connection line 53 and the PN return section 437 and the capacitance of the Y capacitor 80 may be set in the AM band, and the impedance Zpn(f) may be set smaller than the impedance Zmg(f) in the AM band. This allows the common mode current to flow easily through the first return path with a small loop area. This makes it possible to reduce common mode noise in the AM band. In particular, it is preferable to set the resonant frequency in the low frequency range of the AM band (around 500 kHz). This makes it possible to reduce common mode noise in the low frequency range of the AM band where noise is difficult to reduce.

It is advisable to provide the PN return portion 437 of the return conductor 43 so as to face the P bus bar 427 and the N bus bar 428 of the inverter 40. By utilizing mutual inductance, the parasitic inductance of the PN return portion 437 can be reduced. This makes it easier for the common mode current to flow through the first return path, which has a small loop area. This makes it possible to further reduce common mode noise.

A capacitor 90 may be provided that is connected in parallel to at least one of the ground line 45 and the MG return section 438. In high frequency bands such as the FM band, the capacitor 90 becomes the main current path, lowering the impedance. Therefore, common mode noise can be reduced not only in the AM band but also in the FM band.

Other Embodiments
The disclosure in this specification and drawings, etc. is not limited to the exemplified embodiments. The disclosure includes the exemplified embodiments and modifications by those skilled in the art based thereon. For example, the disclosure is not limited to the combination of parts and/or elements shown in the embodiments. The disclosure can be implemented by various combinations. The disclosure can have additional parts that can be added to the embodiments. The disclosure includes the omission of parts and/or elements of the embodiments. The disclosure includes the substitution or combination of parts and/or elements between one embodiment and another embodiment. The disclosed technical scope is not limited to the description of the embodiments. Some disclosed technical scopes are indicated by the description of the claims, and should be interpreted as including all modifications within the meaning and scope equivalent to the description of the claims.

The disclosure in the specification and drawings, etc. is not limited by the claims. The disclosure in the specification and drawings, etc. encompasses the technical ideas described in the claims, and extends to more diverse and extensive technical ideas than the technical ideas described in the claims. Therefore, various technical ideas can be extracted from the disclosure in the specification and drawings, etc., without being bound by the claims.

When an element or layer is referred to as being "on," "coupled," "connected," or "bonded," it may be directly coupled, connected, or bonded to another element or layer, and intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," "directly coupled," "directly connected," or "directly bonded" to another element or layer, no intervening elements or layers are present. Other words used to describe relationships between elements should be construed in a similar manner (e.g., "between" vs. "directly between," "adjacent" vs. "directly adjacent," etc.). As used in this specification, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Spatially relative terms such as "inside," "outside," "back," "bottom," "low," "top," "top," and the like are utilized herein for ease of description to describe the relationship of one element or feature to other elements or features as depicted in the figures. Spatially relative terms may be intended to encompass different orientations of the device during use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "directly below" other elements or features would be oriented "above" the other elements or features. Thus, the term "bottom" can encompass both an orientation of top and bottom. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used in this specification would be interpreted accordingly.

10...shielding system, 20...battery, 21...housing, 23...return conductor, 30...MG, 31...housing, 32...winding, 40...inverter, 41...housing, 41a...outer surface, 41b...inner surface, 41c...first surface, 41d...second surface, 42...electrical component, 421...semiconductor module, 4211...semiconductor element, 422...output terminal block, 423...capacitor element, 424...input terminal block, 425...circuit board, 425G...ground layer, 426...output bus bar, 427...P bus bar, 427a...fastening hole, 428...N bus bar , 428a...fastening hole, 43...return conductor, 431, 435...main body, 432, 434, 436...terminal, 433...embedded part, 437...PN return part, 438...MG return part, 439...remaining part, 44...capacitor, 45...ground line, 50...shield line, 51...inner conductor, 51P...P line, 51N...N line, 52...outer conductor, 53...connection line, 60...shield line, 61, 61U, 61V, 61W...output line, 62...outer conductor, 63...connection line, 70...parasitic capacitance, 80...Y capacitor, 90...capacitor

Claims (16)

A first device (20, 30) having a metal member (21, 31);
A second device (40) having a resin housing (41) and an electric component (42) housed in the resin housing;
a power line (51, 61) connecting the first device and the second device;
Equipped with
The second device has a return conductor (43) electrically connected to the metallic member and providing a return path for a common mode current. The power line is an inner conductor of a shielded wire (50, 60),
2. The shielding system of claim 1, wherein the return conductor is electrically connected to the metal member via an outer conductor of the shield wire. The shielding system according to claim 1 or 2, wherein at least a portion of the return conductor is housed in the resin housing. The shielding system according to claim 1 or 2, wherein the return conductor is inserted into the resin housing. The shielding system according to claim 1 or 2, wherein at least a portion of the return conductor is disposed on the outer surface of the resin housing. The shielding system according to claim 1 or 2, wherein the metal member is a metal housing. The shielding system according to claim 1 or 2, wherein the second device is a power converter. The power converter includes the electrical components constituting a power conversion circuit and a circuit board (425) electrically connected to the electrical components;
The shielding system according to claim 7 , wherein the return conductor is housed in the resin housing and disposed between the electrical component and the circuit board. The shielding system according to claim 1 or 2, comprising a Y capacitor (80) having one terminal connected to the power line and another terminal connected to the return conductor. The first device includes a battery and a rotating electric machine,
The second device includes a power converter,
10. The shielding system according to claim 9, wherein the Y capacitor is connected to the return conductor at a position between the end of the return conductor on the battery side and the end of the return conductor on the rotating electric machine side, the position being closer to the end of the return conductor on the battery side. The first device includes a battery and a rotating electric machine,
The second device includes a power converter,
10. The shielding system according to claim 9, wherein the Y capacitor is connected to the return conductor at a position between the end of the return conductor on the battery side and the end of the return conductor on the rotating electric machine side, the position being closer to the end of the return conductor on the battery side. The first device includes a battery and a rotating electric machine,
The second device is provided with a power converter including a semiconductor element (4211),
a metal member of the battery, a metal member of the rotating electric machine, and the return conductor of the power converter are electrically connected to a body ground;
a Y capacitor (80) having one terminal connected to the power line and another terminal connected to the return conductor;
a first connection line (52, 53) electrically connecting a metal member of the battery and the return conductor;
a second connection line (62, 63) electrically connecting the metal member of the rotating electric machine and the return conductor;
a resonance frequency between an inductance of the first connecting line and the return conductor connecting the metal member of the battery and the Y capacitor, and a capacitance of the Y capacitor is in an AM band;
2. The shielding system according to claim 1, wherein a relationship between an impedance Zpn(f) which is a function of frequency f of a first path from a metal component of the battery via the first connecting line, the return conductor, and the Y capacitor to the semiconductor element, and an impedance Zmg(f) which is a function of frequency f of a second path from the metal component of the battery via a body ground to the semiconductor element satisfies Zpn(f) < Zmg(f) in the AM band range. The power converter has bus bars (427, 428) electrically connected to the power lines between the battery,
The shielding system according to claim 12 , wherein a portion of the return conductor that electrically connects the first connection line and the Y capacitor is disposed opposite the bus bar. The shielding system according to claim 12 or 13, further comprising a ground line (45) for connecting the power converter to the body ground, and a capacitor (90) connected in parallel to at least one of a connection portion of the return conductor that electrically connects the connection portion with the ground line and the second connection line. A resin housing (41);
An electrical component (42) that is housed in the resin housing and is electrically connected to other devices through a power line;
A return conductor (43) electrically connected to a metal member of the other device to provide a return path for common mode noise;
An electrical device comprising: The power line is an inner conductor of a shielded wire (50, 60),
16. The electric device according to claim 15, wherein the return conductor is electrically connected to the metal member via an outer conductor (52, 62) of the shield wire.

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