KR20090005207A - Power converter - Google Patents

Abstract

a capacitor (12) connected to the input side of an inverter circuit (13a); noise suppression means (10a, 10b) arranged at least one of an input side conductor connected to the input side of the inverter circuit (13a) and an output side conductor connected to the output side of the inverter circuit (13a); quantity-of-electricity detectors (11, 19a, 19b, 19c) arranged at the input side conductor or the output side conductor at the opposite side of the inverter circuit of the noise suppression means (10a, 10b); and a control unit (20) for controlling the inverter circuit (13b) according to a quantity-of-electricity detection signal from the quantity-of-electricity detectors. The power converter can suppress the common mode noise without increasing the parts size, the number of parts, or the cost.

Description

Power converter {POWER CONVERTER}

The present invention relates to a power converter having an inverter circuit for converting direct current power supplied to an input side into alternating current power and supplying the load to a load connected to the alternating current.

Background Art Conventionally, power converters having inverter circuits constructed using semiconductor switching elements have been widely used in many industrial fields such as electric vehicles and automobiles. For example, the inverter circuit includes an inverter circuit mounted on an electric vehicle, an input side connected to a wire through a current collector, and an output side connected to a main motor for driving the electric vehicle, and the noise on the input and output conductors of the inverter circuit. There is a power conversion device provided with a core made of a magnetic material for suppression (see Patent Document 1, for example).

Similarly, in a power conversion device mounted in an electric vehicle, a voltage detector is connected to the input side of the inverter circuit, a current detector is connected to the output side of the inverter circuit, and the inverter circuit is based on the voltage detection signal and the current detection signal from these detectors. There is one to control (see Patent Document 2, for example).

Patent Document 1: Japanese Patent Application Laid-Open No. 2004-187368

Patent Document 2: Japanese Patent No. 3747858

Recently, in order to reduce the power consumption associated with high-speed processing, the microcomputer embedded in the control unit of the power converter has been progressing in the low voltage of the operating voltage, and it has recently been about 5 [V]. Microcomputers with low voltage operation of about [V] to 3 [V] are used. Accordingly, in order to prevent malfunction of the control unit and to obtain stable operation of the power converter, it is necessary to suppress the common mode noise current to the control unit.

In order to effectively suppress the common mode noise current to the controller, the impedances for the common mode noise currents of the voltage detector and the current detector provided on the input side and the output side of the inverter circuit are respectively increased or disposed on the input side of the controller that controls the inverter circuit. Although it is conceivable to take countermeasures such as increasing the impedance of the isolation amplifier, taking such countermeasures will result in larger components, an increase in the number of components, and an increase in cost.

An object of the present invention is to reduce the common mode noise current to the control unit without causing components to increase in size, increase in the number of parts, increase in cost, and the like, thereby achieving stable operation even when using a microcomputer operating at a relatively low voltage. To get a power converter.

The power converter according to the present invention includes an inverter circuit for converting DC power supplied to an input side into AC power and supplying the load connected to the output side; A capacitor connected to an input side of the inverter circuit; Noise suppression means provided on at least one of an input side conductor connected to an input side of said inverter circuit and an output side conductor connected to an output side of said inverter circuit; An electric quantity detector provided in the input side conductor or the output side conductor on the anti-inverter circuit side of the noise suppression means; And a control unit for controlling the inverter circuit based on the electric quantity detection signal from the electric quantity detector.

According to the power conversion device according to the present invention, a microcomputer or the like operating at a relatively low voltage can suppress a common mode noise current to the control unit without causing components to increase in size, increase in number of parts, and increase in cost. You can also get stable operation.

1 is a configuration diagram of a power conversion device according to Embodiment 1 of the present invention.

2 is a configuration diagram of a power conversion device according to Embodiment 2 of the present invention.

3 is an explanatory diagram showing an equivalent circuit of a common mode noise current of the power converter according to the first and second embodiments of the present invention.

4 is a configuration diagram of a power conversion device according to the technique 1 on which the invention is based.

5 is a configuration diagram of a power conversion device according to the technique 2 on which the invention is based.

FIG. 6 is an explanatory diagram showing an equivalent circuit of common mode noise current of the power converter according to the techniques 1 and 2 on which the invention is based.

Explanation of the sign

1 line

2 current collector

3 reactor

4 wheel

5 rails

6 power converter

7 Three-Phase AC Motors

10a first core

10b second core

11 voltage detector

12 condenser

13a, 13b inverter module

SU, SV, SW, SX, SY, SZ switching elements

19a, 19b, 19c current detector

20 control unit

22a, 22b, 22c, 22d isolation amplifier

30 discharge resistance

31 discharge element

Before describing an embodiment of the present invention, the technology underlying the present invention will first be described.

Technology underlying the invention 1.

4 is a configuration diagram of a power converter according to the technique 1 on which the present invention is based, and shows an example mounted on an electric vehicle. In FIG. 4, the electric power converter 6 mounted on the electric vehicle is supplied with direct current power from the household wire 1 through the current collector 2. A switch (not shown) is connected to the current collector 2, and a smoothing circuit constituted by the reactor 3 and the capacitor 12 is further connected. The inverter module 13b as an inverter circuit has a three-phase bridge circuit constituted by the switching elements SU, SV, SW, SX, SY, and SZ, and the DC terminal on the input side thereof is disposed between both ends of the capacitor 12. The AC-side terminals of the U-phase, V-phase, and W-phase on the output side are connected to input terminals of a three-phase AC motor (hereinafter referred to as an electric motor) for driving an electric vehicle.

The voltage detector 11 which detects the voltage of the both ends of the capacitor 12 is connected to the DC side terminal of the inverter module 13b, and the current detector 19a which detects the output current of each phase is connected to the AC side terminal of the inverter module 13b. , 19b and 19c are provided respectively. The cathode side of the DC side terminal of the inverter module 13b is connected to the rail 5 via the wheel 4 of the electric vehicle. The inverter module 13b converts the DC power from the capacitor 12 into AC power and outputs it to the electric motor 7. In the regenerative braking of the electric vehicle, AC power generated by the electric motor 7 is converted into DC power and output to the capacitor 12 side.

The voltage detection signal VD from the voltage detector 11 for detecting the voltage across the capacitor 12 and the current detection signal IU from the current detectors 19a to 19c for detecting the current on the output side of the inverter module 13b. IW) is input to the control unit 20 through the isolation amplifiers 22a, 22b, 22c, and 22d. The control unit 20 generates a gate signal G based on these signals and a command input from the outside (not shown), and outputs them to the gates of the switching elements SU to SZ.

Each of the switching elements SU to SZ is controlled based on the gate signal, and supplies the three-phase AC power of the pulse width modulation control (hereinafter referred to as PWM) to the electric motor 7 and the electric motor 7. ) To generate the desired torque. The control unit 20 incorporates a microcomputer (hereinafter referred to as a microcomputer) and is controlled by software.

The hollow annular (ring-shaped) first core 10a made of a magnetic material such as ferrite or amorphous metal is provided on the direct current side, which is the input side of the inverter module 13b, The pair of conductors on the direct current side passes through the inner space portion of the first core 10a. Moreover, the hollow annular (ring-shaped) second core 10b composed of a magnetic material such as ferrite or amorphous metal is provided on the output side of the inverter module 13b, and the U phase, V phase, and W on the output side thereof. Each conductor of the image penetrates the inner space portion of the second core 10b.

The 1st core 10a and the 2nd core 10b actually consist of several core in series, and are comparatively large in size. Therefore, the inside of the metal case housing the power converter 6 composed of the inverter module 13b, the control unit 20, the capacitor 11 and the reactor 3, without being disposed inside the inverter module 13b. It is arranged in the place where there is relatively space. In addition, the current detectors 19a to 19c and the voltage detector 11 are also housed inside the metal casing that houses the power converter 6.

The voltage detector 11 is connected to the input side conductor of the inverter module 13b on the output side of the first core 10a, that is, on the inverter module 13b side of the first core 10a. The current detectors 19a to 19c are provided on the output side conductor of the inverter module 13b on the input side of the second core 10b, that is, on the inverter module 13b side of the second core 10b.

The current detection signals IU, IV, and IW obtained from the current detectors 19a to 19c are used for the control of the electric motor 7, as described above, and the AC terminal, which is a conductor on the output side of the inverter module 13b, In the event that an abnormality such as a short circuit or ground fault occurs, the abnormality is reliably detected and the control unit 20 stops the switching operation of the switching elements SU to SZ to perform the protection operation. use. Accordingly, the current detectors 19a to 19c are located close to the switching elements SU to SZ inside the inverter module 13b so that the abnormal current of the wide range of the output line of the inverter module 13b can be detected. Is placed on. The voltage detector 11 is arranged next to the capacitor 12 in the function of detecting the voltage between both ends of the capacitor 12.

The power converter 6 configured as described above is characterized by a high control voltage of about 1 [MVA] and a high voltage of about 600 [V] to 3000 [V], and a switching element in the inverter module 13b. In the case where (SU to SZ) performs the switching operation, the voltage of the circuit near the switching element changes from 0 [V] up to about 3000 [V] in a few [m] time. Due to this voltage change, a high frequency leakage current is generated through the floating capacitance in the circuit. This leakage current flows into and out of the power converter 6. Such leakage current is called common mode noise current.

In addition, the power converter 6 is often mounted under the bark of the vehicle. When the common mode noise current flows to the vehicle body of the vehicle outside the case of the power converter 6 in a wide range, the common mode noise current flows. A large loop circuit is formed, and the high frequency magnetic flux generated thereby may adversely affect the signal device (not shown) installed near the rail. The first core 10a and the second core 10b provided in the power converter 6 are provided to avoid such adverse effects, and operate as noise suppression means for suppressing the leakage of common mode noise current.

That is, the space inside the first core 10a is penetrated by a pair of conductors on the input side of the inverter module 13b as described above, and the inside space of the second core 10b is the inverter module 13b. It is penetrated by the three conductors on the output side of. Therefore, the 1st core 10a and the 2nd core 10b generate an impedance with respect to the common mode noise current which flows through the some conductor which passed through in the same direction, and suppresses a common mode noise current. In general, the first core 10a and the second core 10b are configured by connecting a plurality of cores in series in accordance with a request for reducing the common mode noise current.

The underlying technology of the invention 2.

5 is a configuration diagram of a power converter according to technique 2, the basis of the present invention. In Fig. 5, the discharge resistor 30 and the discharge element 31 are connected in series, and these constitute an overvoltage suppression discharge circuit. This overvoltage suppression discharge circuit is connected to the capacitor 12 in parallel. The voltage detector 11 is connected to both ends of the discharge element 31. The other structure is the technique 1 and Orient which are the foundation of invention.

The overvoltage suppression discharge circuit constituted by the discharge resistor 30 and the discharge element 31 turns on the discharge element 31 to discharge the charge of the capacitor 12 when the voltage across the capacitor 12 becomes overvoltage. It is set as the structure which discharges to 30, and it can prevent that the inverter module 13b is damaged by overvoltage by this.

The reason why the voltage detector 11 is connected to both ends of the discharge element 31 is that it serves as a function of detecting the voltage at both ends of the capacitor 12 and confirming the operation of the discharge element 31. In the normal time (when the discharge element 31 is turned off), the voltage detector 11 can detect the voltage at both ends of the capacitor 12, and when an overvoltage occurs (when the discharge element 31 is on). Since the detection value of the voltage detector 11 is zero, the controller 20 can determine that the discharge element 31 is on with this, and it is possible to monitor whether the discharge element 31 is operating normally. . In addition, since the inverter module 13b is stopped when an overvoltage occurs, there is no problem in the control operation even if the detected value of the voltage detector 11 is zero.

FIG. 6 is an explanatory diagram showing an equivalent circuit of a common mode noise current in the techniques 1 and 2, which are the basis of the invention shown in FIGS. 4 and 5. In addition, the equivalent circuit shown in FIG. 6 is simplified and expressed in the range which does not impair the physical meaning in order to make it easy to grasp | a phenomenon. In Fig. 6, VN is a common mode noise voltage generated by the voltage change caused by the switching operation of the switching elements SU to SZ, and 4 as the common mode noise current path generated by this common mode noise voltage VN. The opening paths A1, A2, B1, and B2 can be considered.

(1) route A1

The path A1 is a circuit impedance Z1A reaching the first core 10a from the switching elements SU to SZ, an impedance Z2A of the first core 10a, and a power converter from the first core 10a. It is a path which consists of a series circuit of the impedance Z3A of the circuit which returns to the common mode noise source via the exterior of (6) and the case of the power converter 6.

(2) route A2

The path A2 is the impedance Z4A of the circuit reaching the voltage detector 11 from the switching elements SU to SZ, the impedance Z5A of the voltage detector 11 and the isolation amplifier 22a from the voltage detector 11. Series circuit of the impedance Z6A of the circuit reaching the control unit 20 via the circuit, and the impedance Z7A of the circuit returning from the control unit 20 to the common mode noise source via the case of the power converter 6. It consists of a path. Moreover, since the distance from the switching elements SU to SZ to the 1st core 10a is longer than the distance from the switching elements SU to SZ to the voltage detector 11, it has a relationship of Z1A> Z4A.

(3) route B1

The path B1 is the impedance Z1B of the circuit from the switching elements SU to SZ to the second core 10b, the impedance Z2B of the second core 10b, and the power converter from the second core 10b. It is a path which consists of a series circuit of the impedance Z3B of the circuit which returns to the common mode noise source via the exterior of (6) and the case of the power converter 6.

(4) route B2

The path B2 includes the impedance Z4B of the circuit reaching the current detectors 19a to 19c from the switching elements SU to SZ, the impedance Z5B of the current detectors 19a to 19c, and the current detectors 19a to 19c. Impedance Z6B of the circuit reaching the control unit 20 via the isolation amplifiers 22b to 22d from the circuit, and a circuit returning to the common mode noise source from the control unit 20 via the case of the power converter 6. This is a path composed of a series circuit of impedance Z7B. Further, since the distance from the switching elements SU to SZ to the second core 10b is longer than the distance from the switching elements SU to SZ to the current detectors 19a to 19c, the relationship is Z1B> Z4B. have.

In FIG. 6, the common mode noise current flowing out of the power converter 6 by the paths A1 and B1 is suppressed by the impedances Z2A and Z2B of the first core 10a and the second core 10b. The flow of the common mode noise current to the vehicle body or the like outside of the power converter 6 is suppressed extensively, and the formation of the loop circuit having the large common mode noise current is suppressed. As a result, since the high frequency magnetic flux generated by the common mode noise current can be reduced, it becomes possible to reduce the influence on the signal device (not shown) provided near the rail.

As described above, the first core 10a and the second core 10b can suppress the common mode noise current flowing out of the power converter 6 by the paths A1 and B1. It is not possible to suppress the common mode noise current flowing in the apparatus 6 by the paths A2 and B2 through the control unit 20. However, suppressing the common mode noise current flowing through the paths A2 and B2 is essential to prevent the malfunction of the control unit 20 and to obtain stable operation of the power converter 6.

Therefore, in order to increase the impedances Z5A and Z5B with respect to the common mode noise currents of the voltage detector 11 and the current detectors 19a to 19c, noise suppression means is applied to the voltage detector 11 or the current detectors 19a to 19c. (Not shown) or by providing the isolation amplifiers 22a to 22d on the input side of the control unit 20, it functions as impedances Z6A and Z6B to suppress common mode noise currents flowing in the paths A2 and B2. We do with configuration to say.

Next, embodiment of this invention is described.

Embodiment 1.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram of the power conversion device which concerns on Embodiment 1 of this invention, and attaches | subjects the same code | symbol to the same or equivalent part as the technique on which the invention is based.

In the technique 1 on which the above-described invention is based, the voltage detector 11 is connected to the input side conductor of the inverter module 13b at the output side of the first core 10a, that is, at the inverter module 13b side of the first core 10a. In the power conversion device according to the first embodiment of the present invention, as shown in FIG. 1, the voltage detector 11 has an input side of the first core 10a, that is, a half inverter module 13a of the first core 10a. Is connected to the input side conductor of the inverter module 13a. Since the first core 10a has impedance only in the common mode noise current, the voltage detector 11 has an inverter module at the input side of the first core 10a, that is, at the half inverter module 13a side of the first core 10a. Even when connected to the input side of 13a, the voltage across the capacitor 12 can be detected.

In the technique 1 on which the invention is based, the current detectors 19a to 19c have an output conductor of the inverter module 13b on the input side of the second core 10b, that is, on the inverter module 13b side of the second core 10b. In the power converter according to the first embodiment of the present invention, the current detectors 19a to 19c are provided at the output side of the second core 10b, i.e., in the case of the inverter module 13b. It is provided in the output side conductor of the inverter module 13a by the half inverter module 13a side of the 2 core 10b. The current detectors 19a to 19c are disposed outside the inverter module 13a.

In the first embodiment, the switching elements SU to SZ are constituted by an intelligent power module (hereinafter referred to as IPM) or a power module combined with a gate driver having an overcurrent protection function.

In addition, the power module in combination with the IPM or the gate driver with the overcurrent protection function has a function to detect an overcurrent when a short circuit or ground fault occurs in the output conductor, and automatically switch off the switching operation. The sensors 19a to 19c detect and do not have to turn off the switching operation via the control unit 20, so that the overcurrent protection operation can be reliably performed at a higher speed.

Accordingly, in Embodiment 1 of the present invention, the current sensors 19a to 19c are provided on the output side (motor side) of the second core 10b away from the switching elements SU to SZ, but the switching elements SU to. Even when a short circuit or ground fault occurs in the wiring conductor between SZ and the current sensors 19a to 19c, it is possible to protect the switching elements SU to SZ. That is, when a short circuit or a ground fault occurs on the power supply side (the side with the switching elements SU to SZ) than the current sensors 19a to 19c, in the technique which is the basis of the present invention, the overcurrent is applied to the current sensors 19a to 19c. Since a short circuit, a ground fault, and the like cannot be detected by the current sensors 19a to 19c and the switching element cannot be turned off because it does not flow, the power converter may be destroyed, but in the configuration of Embodiment 1 of the present invention, the switching element The SU-SZ itself has an overcurrent protection function, and even when a short circuit or ground fault occurs in the wiring conductor between the switching elements SU-SZ and the current sensors 19a-19c, the switching elements SU-SZ. It is possible to avoid the destruction of the power converter by turning off.

Embodiment 2.

2 is a configuration diagram of a power conversion device according to the second embodiment of the present invention. In FIG. 2, the discharge resistor 30 and the discharge element 31 are connected in series, and these comprise the overvoltage suppression discharge circuit. This overvoltage suppression discharge circuit is connected to the capacitor 12 in parallel. The voltage detector 11 is connected to both ends of the discharge element 31.

Although the voltage detector 11 was arrange | positioned at the output side of the 1st core 10a in the technique 2 which is the foundation of above-mentioned invention, in the power converter which concerns on Embodiment 2 of this invention, as shown in FIG. 11 is arrange | positioned at the input side of the 1st core 10a. Since the first core 10a has an impedance only in the common mode noise current, the voltage detector 11 can detect the voltage across the capacitor 12 even if it is arranged on the input side of the first core 10a.

In the technique 2 on which the invention is based, the current detectors 19a to 19c are arranged inside the casing of the inverter module 13b on the input side of the second core 10b, but according to the second embodiment of the present invention. In the power converter, the current detectors 19a to 19c are arranged on the output side of the second core 10b and also outside the inverter module 13a. Other configurations are the same as those in the first embodiment.

3 is an explanatory diagram showing an equivalent circuit of a common mode noise current in the configuration of the power converter according to the first and second embodiments of the present invention. In addition, the equivalent circuit shown in FIG. 3 is simplified and expressed in the range which does not impair physical meaning, in order to make it easy to grasp | a phenomenon. In FIG. 3, VN is a common mode noise voltage generated by a voltage change caused by the switching operation of the switching elements SU to SZ. As a common mode noise current path generated by this common mode noise voltage VN, Four paths A1, B1, A3, and B3 shown in FIG. 3 can be considered.

Paths A1 and B1 are the same as those in FIG. 6 described in the technology underlying the invention, and thus description thereof is omitted. In Embodiments 1 and 2 of the present invention, instead of the path A2 and the path B2 in the techniques 1 and 2 on which the invention is based, the paths A3 and B3 shown below are provided, respectively.

(1) route A3

The path A3 includes a circuit impedance Z1A reaching the first core 10a from the switching elements SU to SZ, an impedance Z2A of the first core 10a, and an impedance Z5A of the voltage detector 11. And common mode noise via the impedance Z6A of the circuit reaching the control unit 20 from the voltage detector 11 via the isolation amplifier 22a and the case of the power converter 6 from the control unit 20. It is a path which consists of a series circuit of the impedance Z7A of the circuit returned to a circle.

(2) route B3

The path B3 is the impedance Z1B of the circuit from the switching elements SU to SZ to the second core 10b, the impedance Z2B of the second core 10b, and the impedances of the current detectors 19a to 19c ( Z5B), the impedance Z6B of the circuit reaching the control unit 20 from the current detectors 19a to 19c via the isolation amplifiers 22b to 22d, and the case of the power converter 6 from the control unit 20. This is a path composed of a series circuit of impedance Z7B of a circuit which returns to a common mode noise source via.

According to the path A3 and the path B3 in the embodiment of the present invention, the voltage detector 11 is provided from the switching elements SU to SZ, respectively, in comparison with the path A2 and the path B2 in the technique (FIG. 6) on which the invention is based. The impedance Z4A of the circuit reaching to becomes the circuit impedance Z1A (Z1A> Z4A) reaching the first core 10a from the switching elements SU to SZ, and the current detector 19a from the switching elements SU to SZ. The impedance Z4B of the circuit reaching ˜19c becomes the circuit impedance Z1B (Z1B> Z4B) from the switching elements SU to SZ to the second core 10b, and the impedance of the first core 10a It can be seen that the impedance Z2B of the Z2A) and the second core 10b is increasing. That is, according to the embodiment of the present invention, the control unit (B) is controlled by the first core 10a and the second core 10b originally installed for suppressing the common mode noise current to the outside of the power converter 6. It can be seen that the common mode noise current to 20 can also be suppressed.

Thus, according to the power conversion apparatus by Embodiment 1 and 2 of this invention, when the voltage of the capacitor 12 can be detected, and when the conductor which is the output line of the inverter module 13a has an abnormality, such as a short circuit and a ground fault, In addition, it is possible to maintain the overcurrent protection function which reliably detects this and stops switching, and further increases the size of the component by providing noise suppression means in the voltage detector 11 or the current detectors 19a to 19c. It is possible to obtain a power converter that can suppress common mode noise current without causing an increase in the number and increase in cost, and can obtain stable operation even with a microcomputer of a low voltage operation in recent years.

In addition, the structure shown in Embodiment 1 and 2 is an example of the structure of this invention, It is also possible to combine with another well-known technique, and changes are comprised, for example, abbreviate | omitting a part in the range which does not deviate from the mind of this invention, Not to mention the possibility.

For example, in Embodiments 1 and 2 of the present invention, the voltage detector is arranged on the input side of the inverter module and the current detector is arranged on the output side of the inverter module. The voltage detector may be disposed on the output side of the inverter module. In addition, only one of the first core 10a or the second core 10b may be provided with the electric quantity detector on the side other than the inverter module. Moreover, you may use the switching element which does not have an overcurrent protection function.

In addition, the power conversion device according to the present invention may be supplied to an AC power supply from a current collector and converted to DC power by a converter, and then applied to a power conversion device having a configuration input to an inverter module. So-called power supply of constant voltage and constant frequency to the load by connecting a load other than an electric motor to the output side, for example, through a transformer and a smoothing circuit, such as a vehicle air conditioner or a lighting device, and performing constant voltage constant frequency operation of the inverter. It is also possible to apply to an auxiliary power supply.

The power converter according to the present invention can be applied to various related fields such as automobiles, elevators, power systems, as well as electric railways.

Claims (6)

An inverter circuit for converting DC power supplied to the input side into AC power and supplying the load connected to the output side; A capacitor connected to an input side of the inverter circuit, Noise suppression means provided on at least one of an input side conductor connected to an input side of said inverter circuit and an output side conductor connected to an output side of said inverter circuit, An electric quantity detector provided on the input side conductor or the output side conductor on the anti-inverter circuit side of the noise suppression means; And a control unit for controlling the inverter circuit based on an electric quantity detection signal from the electric quantity detector. The method according to claim 1, And an overvoltage suppression discharge circuit connected to the input side conductor at the half inverter circuit side of the noise suppression means. The method according to claim 1, The said noise suppression means is comprised by the annular magnetic material, and the said conductor has penetrated the hollow part, The power converter characterized by the above-mentioned. The method according to claim 1, The inverter circuit is constituted by a plurality of semiconductor switching elements that are switched and controlled by a switching signal given from the controller, And the control unit generates the switching signal based on the electricity quantity detection signal from the electricity quantity detector. The method according to claim 4, And the semiconductor switching element has an overcurrent protection function. The method according to any one of claims 1 to 5, And an input side of the inverter circuit is connected to a wire through a current collector, and an output side of the inverter circuit is connected to an electric motor for driving the electric vehicle.

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