JPH11355910A - Power converting device for electric car - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the interference of electronic devices or radio equipment to be caused by the higher harmonic current which arises from semiconductor switching elements, in a power converting structured with semiconductor switching elements. SOLUTION: The DC side negative pole of a power converting device 8 is connected to the casing of an induction motor 5 and the casing of the induction motor 5 to a grounding device 7 with electric wires 50, 60 respectively. The electric wire 50 between the DC side negative pole of a power converting device 8 and the casing of an induction motor 5 is wired by twisting it with an electric wire between the AC side output of the power converting device 8 and the induction motor 5. This structure assuredly returns the higher harmonic current which spills out of the electric wire between the AC side output of the power converting device 8 and the induction motor 5 or from the induction motor 5 to the power converting device 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter for an electric vehicle, and more particularly to a technique for suppressing a harmonic disturbance generated by the power converter.

[0002]

2. Description of the Related Art As a grounding circuit in a conventional DC electric car, as shown in Japanese Patent Application Laid-Open No. 62-213501, the DC side negative electrode of a power conversion device is once grounded to a vehicle body and then connected to a grounding device. ing.

[0003]

In the case where the power converter is configured to switch the input DC voltage by the semiconductor switching element and control the frequency and voltage of the output AC voltage by controlling the switching time, Harmonic current flows out of the power conversion device due to a sharp voltage change caused by the above, and sometimes causes a failure in electronic devices and wireless devices mounted on the electric vehicle.

FIG. 3 shows a configuration of a ground circuit of a conventional electric power converter for electric vehicles. The DC power of the power supply 43 taken in from the overhead line 41 via the current collector 1 is supplied to the power converter 8 via the circuit breaker 2 and the filter reactor 3.
Is connected to the DC side positive electrode. A filter capacitor 4 is connected between the positive electrode and the negative electrode on the DC side of the power converter, and the filter reactor 3 and the filter capacitor 4 constitute a filter circuit.

[0005] The power conversion device 8 for converting DC to AC is constituted by a three-phase inverter composed of semiconductor switching elements IGBTs 11 to 16, and its AC output is connected to the three-phase induction motor 5.

[0006] The DC side negative electrode of the power converter 8 is grounded to the vehicle body by the ground terminal block 6, then connected to the grounding device 7 and connected to the negative electrode of the power supply 43 via the rail 42.

Here, the AC voltage output from the power converter 8 is considered.

[0008] Since the power converter 8 generates an AC voltage by controlling the switching time of the IGBTs 11 to 16, the AC voltage has a rectangular shape. When the IGBT is switched, the potential of the AC output point of the power converter 8 becomes DC. The potential of the power supply 43 changes to the potential of the vehicle body.

In this case, the power converter 8 and the induction motor 5
And the vehicle body, there are stray capacitances 21 to 23 in the electric wire covering, and the induction motor 5 has a stray capacitance 24 in the coil insulator. Therefore, when the potential of the AC output point of the power converter 8 with respect to the vehicle body changes, the harmonic current flows out through the stray capacitances 21 to 24,
Stray currents 31 and 32 flow through the vehicle body.

[0010] The stray current adversely affects electronic devices, wireless devices, and the like.

As typified by IGBT semiconductor switching elements, recent semiconductor advances have increased the switching speed of semiconductor switching elements, and have resulted in lower noise and lower loss in power converters. The voltage change at the output point becomes steep, and the outflow of the stray current described above increases.

The present invention is based on this outflow of harmonic current.
An object of the present invention is to provide a power conversion device capable of suppressing an obstacle to an electronic device, a wireless device and the like.

[0013]

SUMMARY OF THE INVENTION The above-mentioned problem is caused by the fact that harmonic current flows out through electric wires connecting the power converter and the induction motor and stray capacitance existing in the coil of the induction motor and flows through the vehicle body as stray current. It is in.

The harmonic currents are represented by stray currents 31 and 32 in FIG.
As shown in (1), the stray currents 31 and 32 that have flowed out return to the power conversion device 8 because the power conversion device 8 is the generation source if the source is traced back.

[0015] In order to solve the above-mentioned problem, a stray current is suppressed from flowing into the vehicle body by providing a path through which the harmonic current flowing out of the electric wire or the induction motor flows more easily than the vehicle body and returning the harmonic current to the power converter. This is achieved by:

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a grounding circuit of a vehicle power converter according to an embodiment of the present invention. Note that the reference numerals in the configuration of FIG. 6 are the same as the same reference numerals shown in FIG.

The difference from FIG. 3 is that an electric wire 5 is connected between the negative electrode on the DC side of the power converter 8 and the case of the induction motor.
Numeral 0 is wired so as to be close to a three-phase line connecting the AC output of the power converter 8 and the induction motor 5, and the DC negative electrode of the power converter and the case of the induction motor 5 are electrically connected. . The case of the induction motor and the grounding device 7 are
Since it is connected by the electric wire 60 and the grounding device is connected to the rail 42, the case of the induction motor and the rail are electrically connected.

In the system shown in FIG. 1, the three-phase line on the AC side output of the power converter 8 is closer to the electric wire from the negative electrode on the DC side of the power converter 8 so that the mutual capacitive coupling becomes stronger. Since the harmonic current flowing out of the three-phase line returns to the power converter 8 positively, this serves to suppress the harmonic current flowing out of the vehicle body. In addition, by connecting the case of the induction motor 5 to the electric wire from the negative electrode on the DC side of the power converter 8, the harmonic current flowing out to the case via the stray capacitance of the coil of the induction motor 5 is positively converted to power. It is also returned to the device 8, which acts to suppress the outflow of the harmonic current to the vehicle body.

FIG. 2 shows another embodiment of the present invention, which differs from FIG. 1 in the following point. The shielded wire 51 is used to connect the power converter 8 and the induction motor 5.
Is used for connection between the AC output of the power converter 8 and the induction motor 5, and the shield part of the shield wire 51 is used for part of the connection between the DC negative electrode of the power converter 8 and the case of the induction motor 5. By using this shielded wire, the capacitive coupling between the three-phase line on the AC side output of the power converter 8 and the wire from the negative electrode on the DC side of the power converter 8 is strengthened, so that the three-phase line flows out of the three-phase line. The active harmonic current is positively returned to the power conversion device 8 to suppress the outflow of the harmonic current to the vehicle body. This operation can be expected to be larger than that of the embodiment of FIG.

In the embodiment shown in FIG. 2, the power converter 8
The DC side negative electrode and the case of the induction motor 5 were connected by an electric wire (not shown) with the shield part of the shield wire as a part, but an electric wire was connected between the DC side negative electrode of the power converter 8 and the case of the induction motor 5. 2, the same effect as in FIG. 2 can be obtained.

[0022]

As described above, according to the present invention,
In an electric vehicle power converter, wiring between the power converter and the induction motor, and suppressing the harmonic current flowing out of the induction motor, and suppressing the stray current flowing through the vehicle body,
The effect is obtained that it is possible to suppress the trouble to be given to the electronic equipment and the signal equipment.

[Brief description of the drawings]

FIG. 1 is a ground circuit of a power conversion device according to an embodiment of the present invention.

FIG. 2 is a ground circuit of a power conversion device according to another embodiment of the present invention.

FIG. 3 is a ground circuit of a conventional electric power converter for electric vehicles.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Current collector, 2 ... Contactor, 3 ... Filter reactor,
DESCRIPTION OF SYMBOLS 4 ... Filter capacitor, 5 ... Induction motor, 7 ... Grounding device, 8 ... Power conversion device, 11-16 ... Semiconductor switching element (IGBT), 41 ... Overhead wire, 42 ... Rail, 43
... DC power supply, 50, 60 ... electric wire, 51 ... shielded wire.

Claims (2)

[Claims] 1. A power converter for converting a DC voltage to an AC voltage by switching-controlling a plurality of semiconductor switching elements, wherein a DC-side positive electrode is connected to a positive electrode of a DC power supply via a current collector. In a power converter for an electric vehicle, a DC negative electrode of the device is connected to a negative electrode of a DC power supply via a grounding device, and an AC output of the power converter is connected to an induction motor for driving an electric vehicle. The DC-side negative electrode of the power converter and the case of the induction motor, and the case of the induction motor and the grounding device are connected by wires, respectively, and between the DC-side negative electrode of the power converter and the case of the induction motor. The wire is
A power converter for an electric vehicle, wherein the power converter is wired close to an electric wire between an AC output of the power converter and the induction motor. 2. The power converter according to claim 1, wherein the electric wire between the negative electrode on the DC side of the power converter and the case of the induction motor is a shield part of a shielded wire, and the AC output of the power converter and the output of the induction motor are connected. An electric vehicle power converter, wherein an electric wire uses the core wire of the shielded wire.