JPS61191269A - Voltage type inverter - Google Patents

Abstract

PURPOSE:To effectively prevent the erroneous operation of a leakage breaker with an inexpensive construction by connecting capacitors between DC lines at the output side of a converter and a ground. CONSTITUTION:Capacitors 9a and 9b are respectively connected between a positive polarity DC line 10a and a negative polarity DC line 10b for supplying the output of a converter 1 to a smoothing condenser 2 and an inverter 3. A high frequency leakage current is supplied from capacitors 9a, 9b provided between the DC lines 10a, 10b and a ground 7, and a high frequency leakage current flowed to 3-phase AC power source lines R, S, T is reduced to prevent a leakage breaker 6 from erroneously operating.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a voltage source inverter device, and more particularly to a voltage source inverter device that prevents malfunction of an earth leakage breaker connected to an AC power source.

[Prior art]

A voltage source inverter device uses AC power as input and performs PWM
By applying control, it is converted into a p1 variable voltage variable frequency AC power source and outputted, and is often used as a drive control circuit for, for example, an induction motor.

FIG. 2 is a circuit diagram showing an example of a voltage source inverter device 9 commonly used in the past.
The quotient Jll11 supplied through the -8-T is converted into a single-phase short current power by full-wave rectification in the converter circuit 1, and then smoothed in the smoothing capacitor 2. The thick current wave smoothed in this way is subjected to PWM control in the inverter circuit 3, so that the voltage and frequency are varied and it becomes 93-phase AC wave.
It is supplied to an induction motor 5 via a distribution line 4. When the earth leakage breaker 6 is connected to such a voltage source inverter device, the output voltage of the voltage source inverter device changes in a stepwise manner, so that the charging current flows through the leakage capacitance of the induction motor 5, the distribution line 4, etc. Since this charging current flows, there is a problem that the earth leakage breaker 6 may malfunction due to misidentification of this charging current as a grounding current. For this reason, when the earth leakage breaker 6 is provided in the inverter device having the above-mentioned configuration, for example, the method disclosed in "New Drive Electronics" published by Denki Shoin, edited by Naohiko Ueyama, page 100, paragraphs 3, 8, and 7. As shown in FIG. 2, a filter is constructed by connecting capacitors 8 between the three-phase AC power line R-8-T and the ground 7, respectively.

In a circuit configured in this way, when the output voltage of the inverter circuit changes stepwise, a leakage current flows to the ground via the leakage capacitance, but this leakage current flows through the three-phase AC power supply line R-8. Since the current is supplied from the capacitors 8 connected between the -T and the ground T, the earth leakage circuit breaker 6 is prevented from malfunctioning due to such leakage current.

[Intermediate point that the invention attempts to solve]

However, in the circuit with the above configuration, the output voltage of the inverter circuit changes in a stepwise manner, which prevents the earth leakage breaker from malfunctioning due to high-frequency leakage current flowing to the ground via the leakage capacitance. If the capacity of the capacitor is increased to reduce high-frequency leakage current, the leakage current of the commercial power supply supplied to the three-phase AC power line R-8-T will increase, causing the problem that the earth leakage breaker will malfunction. There is.

The present invention was made to solve the above problem, and an object of the present invention is to provide an inverter device that prevents malfunction of an earth leakage breaker due to leakage current corresponding to the commercial power frequency.

[Means for solving problems]

Therefore, the inverter device according to the present invention has a capacitor connected between each output line of the converter circuit constituting the inverter device and the ground.

[Effect]

In the inverter device configured in this way, since the capacitors are connected between the DC line and the ground, the output of the inverter circuit can be increased without increasing the leakage current of the commercial frequency flowing through the three-phase AC power line. By changing stepwise, high-frequency leakage current flowing through the leakage capacitance is prevented from flowing to the earth leakage breaker.

[Embodiments of the invention]

FIG. 1 shows an example of an inverter device according to the present invention. Five connections are made between the positive DC line 10a and the negative DC line 10b, which supply the output of the converter circuit 1 to the smoothing capacitor 2 and the inverter circuit 3, and the ground T, respectively. The difference from the capacitor shown in FIG. 2 is that capacitor 8 is removed and capacitors 9m and 9b are provided.

In a circuit configured in this way, when the output of the inverter circuit 3 changes stepwise, a high-frequency leakage current flows through the leakage capacitance between the distribution line 4 and the visiting motor 5 and the ground T. It will leak to the ground T. This high frequency leakage current is absorbed by capacitors 9 installed between each DC line and the ground T.
Since it is supplied from a and 9b, the high frequency leakage current flowing to the three-phase AC power line R・S-T is reduced,
Malfunction of the earth leakage interrupter 6 will be prevented.

In addition, it is connected to the converter circuit 1 and has a 10m flow line.
, 10b maintain a stable position with respect to the ground 1, so by connecting the capacitors 9a and 9b, there is almost no horse frequency leakage current tl flowing through the capacitors 9m and 9b. Therefore, this capacitor 9a, 9
Even if the filter effect against high frequency leakage current is enhanced by increasing the capacity of b, the three-phase AC power line R-8-
This solves the problem that the leakage current of the commercial frequency component flowing through T increases and causes the earth leakage breaker to malfunction.

〔Effect of the invention〕

As explained above, in the inverter device according to the present invention, a capacitor is connected between each DC line and the ground on the output side of the converter circuit. It has an excellent effect of reliably preventing malfunction of the circuit breaker.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of an inverter device according to the present invention, and FIG. 2 is a circuit diagram showing a conventional inverter device. 1...Converter circuit, 2...Smoothing capacitor, 3
...Inverter circuit, 4...Wiring, line, 5...
Electric conduction motor, 6...Earth leakage breaker, 1...Grounding, 9*
, sb...capacitor, 10m, 10b...DC line. Note that the same parts in the figures are indicated using the same symbols. Agent: Masuo Ohmaki (and 2 others) Written amendment to yφt procedure (voluntary) March 77, 1949 To the Commissioner of the Japan Patent Office: W.
Indication of the case: Japanese Patent Application No. 14826/1982 2, title of the invention Voltage-type inverter device 3, person making the amendment Relationship to the case Patent applicant address: 2-2-3 Marunouchi, Chiyoda-ku, Tokyo Name (601) Mitsubishi Electric Corporation Representative Moriya Shiki 4, Agent 5, Subject of amendment (1) Detailed description of the invention in the specification column 6, Contents of amendment (1) Page 2 of the specification tube, line 10, “Single-phase Correct the phrase "DC power supply" to "1 DC voltage." (2) On page 2, line 12, "DC power supply" is corrected to "DC voltage."

Claims (1)

[Claims] A converter circuit that converts commercial AC power to DC, a smoothing capacitor that smoothes the output of this converter circuit, and the DC smoothed by this smoothing capacitor is used as a power source to output variable voltage variable frequency AC power to the load. A voltage source inverter device comprising: an inverter circuit for supplying the voltage; and capacitors connected between each DC line connected to the output end of the converter circuit and ground.