JPH02133035A - Protective circuit for inverter - Google Patents

Abstract

PURPOSE:To protect the damage of an inverter circuit by detecting and storing the input of a commercial three-phase AC power to the output terminal of an inverter device and preventing the operation of an inverter control circuit even when a starting signal is input to the control circuit. CONSTITUTION:When a commercial three-phase AC power is applied to the output terminal of an inverter device, the power circuit 8 of a control circuit 9 conducting ON-OFF control at a specified timing is operated, and the control circuit 9 is operated. Consequently, a voltage signal is stored in a storage cell 12 such as a flip-flop. The output signal of the storage circuit 12 is connected to the reset signal terminal of the control circuit 9, and the operation of the control circuit 9 can be prevented when the commercial three-phase AC power is applied to the output terminal of the inverter device, thus obviating the damage of the inverter circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a protection circuit for an inverter device.

[Conventional technology]

Figure 3 is a block diagram of the main circuit of a conventional inverter device. In the figure. +3) IIi A converter circuit that rectifies commercial three-phase AC voltage and converts it into DC. (4) is an electrolytic capacitor for smoothing the DC voltage rectified by the converter circuit. (5) is a resistor for preventing the converter circuit from being damaged by rush current flowing into the electrolytic capacitor. +1) is an electromagnetic contactor for short-circuiting the inrush current limiting resistor after a time limit. (7) is an inverter circuit composed of a plurality of transistors for converting a DC voltage into an AC voltage of a predetermined voltage and a predetermined frequency by controlling on/off of a plurality of switching means at predetermined timings. (9) is a control circuit for controlling the inverter circuit. (8) is a power supply circuit that outputs a predetermined voltage by inputting the DC voltage and supplies power to the control circuit; (6) is a power supply circuit that supplies power to the output sides U, V, and W of the inverter circuit; An inrush current limiting resistor that prevents the inverter circuit (7) from being damaged by the inrush current flowing through the electrolytic capacitor (4) when a phase alternating current power source is applied.

(2) is an electromagnetic contactor that attracts the contact point (2a) and short-circuits the inrush current limiting resistor (6) when a commercial three-phase AC power source is applied to the input side of the converter circuit (3).

Next, the operation of this circuit will be explained.

First, under normal conditions, the commercial 3-phase AC power supply is connected. RS, TMC
[When the sequel was sold.] [Magnetic contactor (1). +21 75
During the time period until Z starts moving, the DC current converted by the converter circuit (3) charges the electrolytic capacitor (5) via the inrush current limiting resistor (4). After the time limit, the electromagnetic contactor (1) operates and the contacts (1a) connected in parallel to both ends of the inrush current limiting resistor (5) are attracted, shorting the inrush current limiting resistor {5}. Similarly, the electromagnetic contactor (2) operates, and the contacts (2a) connected in parallel to both ends of the inrush current limiting resistor (6) attract and short-circuit the inrush current limiting resistor (6). Also. The DC voltage smoothed by the electrolytic capacitor (4) is . It is converted to a predetermined voltage by the power supply circuit (8) and operates the control circuit (9). By the signal of the control circuit (9). By turning on and off multiple transistors of the inverter circuit (7), the output terminal U,
V. W outputs the DC voltage as an AC voltage of a predetermined voltage and frequency, and the inverter device operates normally.

Next, the output terminals U and V of the inverter device. A case where a commercial three-phase AC power source is applied to W will be explained.

As an example, as shown in Figure 2. Inverter circuit (7)
The DC current converted by the diode (DUP-DWN) included in the inverter circuit (7) is charged to the smoothing capacitor (4) through the diode (DUP) included in the inverter circuit (DUP) and the inrush current limiting resistor (6). The circuit (7) will not be damaged.

[Problem to be solved by the invention]

Since the conventional inverter device is configured as described above, the inverter device generates a predetermined voltage as its own control power source from the DC voltage generated by the output of the electrolytic capacitor of the inverter circuit. As mentioned above, the output terminal U. of the inverter device. When connected to V and W. As mentioned above, the inverter circuit 《7》 is not damaged. In order for the electrolytic capacitor (4) to be charged normally, the power supply circuit (8)
is working properly. Power is supplied to the control circuit (9). Therefore, when a start signal is input to the control circuit (7), the transistors of the inverter circuit (7) become conductive. The commercial three-phase power supply was short-circuited inside the inverter circuit (7). As a result, the inverter circuit is damaged and a power supply trip occurs.

This invention... This was done to solve the above problems, and the output terminal U of the inverter device. Even if a commercial three-phase AC power supply is input to V and W and a start signal is input to the inverter control circuit described above, the inverter protection system protects the inverter circuit from being short-circuited and damaged. The purpose is to provide a fishing device.

[Failure to solve the problem]

The inverter protection device according to this invention is. When a commercial three-phase AC power source is applied to the output terminals U, V, and W of the inverter device. Also, when a start signal is input to the inverter control circuit at the same time. A storage means for detecting and storing the fact that a commercial three-phase AC power supply is input to the output terminals Uy and W of the inverter device.
In the case where the storage means is stored. The inverter control circuit is provided with an operation inhibiting means that does not operate the inverter control circuit that controls on/off of a plurality of switching means at predetermined timings even if a start signal is input to the control circuit.

[Effect]

In this invention. Inverter device output terminals U, V,
If a commercial 3-phase AC power supply is input to W, an incorrect connection will be detected. Furthermore, the inverter circuit operates even if a start signal is input to the inverter control circuit, which controls on/off multiple switching means at predetermined timings. Prevent damage to the circuit.

〔Example〕

below. An embodiment of the present invention will be described with reference to the drawings. 1st
In the figure, 11 is the output side ty, v. of the inverter device. lol
An optical isolation element that detects current flowing through the inrush current limiting resistor (6) when a commercial three-phase AC voltage is input to the terminal.
(111 is a resistor that limits the current flowing to the optical insulation element,
112 is the output side U. v. This is a storage circuit such as a flip-flop that temporarily stores a signal at the time when a commercial three-phase AC voltage is input to the W terminal. The other configurations are similar to the conventional circuit diagram shown in FIG.

Next, the operation will be explained.

First, when a commercial three-phase AC power source is applied to the R, S, and T terminals on the input side of the converter circuit (3) under normal conditions, the converter performs the same operation as the conventional one.

next. Output terminal U of the inverter device. Commercial 3 for V and W
When phase AC power is applied. In Fig. 1, the diode (DUP) included in the inverter circuit (7),
Inrush current limiting resistance《6》. Electrolytic capacitor C4). Diode (DVN) included in the inverter circuit (7)
When a current flows through the electrolytic capacitor (4) and the DC voltage is charged, the power supply circuit (8) of the control circuit (9) which controls on/off the plurality of switching means at a predetermined timing is operated. The control circuit operates. At the same time, a voltage is generated across the inrush current limiting resistor (6). This generated voltage causes a current to flow through the photoinsulating element αG via the resistor U. As a result. It becomes possible to obtain a voltage signal on the secondary side of the optical insulation element αG. The optical insulation element +
The voltage signal output to the secondary side of Il1 is stored in a storage element a3 such as a flip-flop. The memory circuit α2
The output signal is connected to a reset signal terminal of a control circuit (9) that controls on/off of a plurality of switching means at predetermined timings. Output terminal U of inverter device
．． v. At the time when commercial three-phase AC power is applied to W. 9. The control circuit (9) can prevent the operation. It becomes possible to prevent damage to the inverter circuit. I explained the above-mentioned escape using DUP and DVN. Diode (DU) included in the inverter circuit (7)
P-DWN) for all combinations of diodes except for one arm among the six. The protection function described above can be achieved.

In FIG. 1, the optical insulation element of (l [l) can be replaced with a pulse transformer.

〔Effect of the invention〕

As described above, according to this invention. Output terminal U of the inverter device. v. Even if a commercial 3-phase AC power source is input to W, incorrect wiring is detected. The inverter control circuit is operating. Short circuit in the inverter circuit. This has the effect of preventing damage to the inverter circuit.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an inverter device using an inverter protection circuit according to the present invention. Figure 2 shows the current flow when a commercial three-phase AC power source is applied from the output terminals U, V, and W in a conventional inverter. FIG. 3 is a block diagram of a conventional inverter device. In the figure, (1) and (2) are electromagnetic contactors, (3) is a converter circuit, and (4) is an electrolytic capacitor. (5) and (6)
is the inrush current limiting resistance. (7) is an inverter circuit. (8)
is the power supply circuit, and (9) is the control circuit. αG is a photo-insulating element. a
υ is resistance. α2 is a memory circuit. Note that the same reference numerals in each figure indicate the same or equivalent parts.

Claims (1)

[Claims] A converter circuit that converts a commercial three-phase AC power supply into DC, an electrolytic capacitor that smoothes the DC voltage output from the converter circuit, and a plurality of switching means for controlling the DC voltage on and off at predetermined timing. , in an inverter device comprising an inverter circuit composed of a plurality of transistors for converting a DC voltage into an AC voltage of a predetermined frequency, a first resistor is provided between the positive terminal of the electrolytic capacitor and the positive terminal of the inverter circuit. contacts of an electromagnetic contactor are inserted in parallel to both ends of the first resistor to attract the same moment when three-phase AC power is applied to the converter circuit, and one of the second resistors is further inserted to the positive terminal of the inverter circuit. a terminal of the second resistor is connected, an anode terminal of a photocoupler is connected to the other terminal of the second resistor, a cathode terminal of the photocoupler is connected to a positive electrode of the smoothing capacitor, and a memory stores an output signal of the photocoupler. circuit, and the output signal of this memory circuit is further connected to a reset signal circuit of an inverter device, and when a commercial three-phase AC power source is applied to the output terminal of the inverter circuit of the inverter device, , the inverter circuit is protected from damage, and the signal output from the photocoupler is used to remember that a commercial three-phase power supply is applied to the output terminal of the inverter device, thereby protecting the inverter device from damage. Characteristic inverter circuit.