JPS619163A - Protecting device of self-extinguishing switching element - Google Patents

Abstract

PURPOSE:To reduce the size and to improve the reliability of a protecting device of a self-extinguishing switching element by varying a current controlled by the element in response to the decrease in the voltage of a power source of a gate current generator of the element. CONSTITUTION:The output of an inverter 14 which has a GTO thyristor 6 and a power source 13 is connected with a load 7, and the thyristor 6 is driven from a power source 10 for a gate current generator through gate current generators 11, 12. Current and voltage supplied to the load 7 are detected at 9 by a current detector 8, compared by a comparator 2 with a current command 1, and input to a pulse width modulation controller 3. When an overcurrent is detected by a detector 5, the thyristor 6 is turned OFF. In this case, a voltage detector 15 for detecting the voltage of the power source 10 for the gate current generator is provided, the output is connected with the detector 5 and the comparator 2, and when the voltage drops, the output current and the overcurrent detecting level of the inverter 14 drop.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a protection device for a self-extinguishing switching element, and particularly to a protection device suitable for preventing damage to the switching element.

[Background of the invention]

One of the self-extinguishing switching elements is a gate turn-off thyristor (hereinafter abbreviated as GTO thyristor).

Since the switching characteristics of a GTO thyristor strongly depend on the gate driving conditions, for example,
As disclosed in Publication No. 1, etc., it is important to supply an appropriate gate current.

GTO in Figure 2? The figure shows a gate current waveform suitable for driving the iris. In the figure, during turn-on, a gate current IGF that is two to three times the minimum ignition gate current IGT of the element is passed for several microseconds to accelerate turn-on, thereby shortening the turn-on time and reducing switching loss. In addition, Iate is applied to ensure continuity.

At turn-off, by flowing a reverse polarity gate current IOR with a peak value of at least 1/3 to 1/4 of the controllable current and a high dxayt/dt for about 10 μs,
This shortens turn-off time, reduces switching loss, and suppresses local current concentration inside the GTO.

If such an appropriate gate current is not supplied for some reason, the GTO element will be damaged due to excessive switching loss or local overheating due to local current concentration.

FIG. 3 shows an example of a gate current generation circuit.

In FIG. 3, on-gate current IGF flows by closing switch 31, and off-gate current IGR flows by closing switch 32. Also, 10 guns have switch 33.34
can be switched alternately. In such a circuit, the gate current is determined by the turns ratio of the transformers 36 and 37, the voltage of the power supply section 35, and the wiring inductance of the gate circuit. The turns ratio of the transformer and the wiring inductance are constant, but the power supply section 35
The voltage of changes.

Changes in power supply voltage directly affect gate current. The voltage drop is due to the gate current IGF, IGI peak value and d! /dt, which not only leads to an increase in the switching loss of the GTO thyristor 39 but also may destroy the device.

FIG. 4 shows a block diagram of a part of conventional current control of a variable voltage/frequency inverter for a vehicle using the GTO thyristor 6.

In FIG. 4, the current controlled by the GTO thyristor 6 is determined by comparing the current command 1 and the output 9 of the current detector 8 with the comparator 2.
controlled.

Also, as a protection against excessive load current, the current detector 9 is detected by the overcurrent detection circuit 5 and the gate logic circuit 4 performs a logic operation. D. Turn off the GTO thyristor 6.

If the GTO thyristor 6 is turned off with a current that exceeds the controllable current, it will definitely be damaged, so the overcurrent detection level is set taking into account the control delay time, etc., and the overcurrent detection level is set to ensure that the current that exceeds the controllable current is never controlled. I have to.

In this way, the conventional gate turn-off
Gristaro's control and protection system requires measures such as providing a constant voltage source in order to prevent the switching capability from decreasing due to a voltage drop in the gate current generators 11 and 12 of the device, which increases the size of the device. There were drawbacks such as reduced reliability.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for preventing damage to a gate current generator of a self-extinguishing switching element caused by a drop in power supply voltage.

[Summary of the invention]

The switching performance of a GTO thyristor is closely related to gate drive, and with inappropriate gate current, the device cannot be used at its rated specifications.

The key point of the present invention is to limit the current controlled by the GTO thyristor when the power supply of the gate current generating device decreases, thereby preventing damage to the device.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, the output of an inverter device 14 comprising an inverter device power supply 13 including a GTO thyristor 6 and a filter 2 to a circuit is connected to a load 7.

The gate of the GTO thyristor is a gate current generator 11.1 that is supplied with power from the gate current generator power supply 10.
2 receives the logic of the gate logic circuit 4 and drives it. The gate current generators 11 and 12 are the same device and are provided in all the GTO thyristors 6, and drive each GTO thyristor 6. The current and voltage supplied to the load 7 (in this block diagram, current control will be explained as an example) are detected by the current detector 8 and output 9, compared with the current command 1 by the comparator 2, and the GTO The signal is input to a pulse width modulation control circuit 3 that controls the gate of the thyristor 6 on and off.

The output of the pulse width modulation control circuit is gated logic circuit °4, which adds logic restrictions such as gate start, stop, and three-phase distribution. Even when the overcurrent detection circuit 5 that detects an overcurrent of the load current is activated, the GTO thyristor 6 is turned off after receiving the logic regulation of the gate logic circuit 4.

The output of the voltage detector 15 that detects the voltage of the power supply 10 for the gate current generator is connected to the overcurrent detector 5 and the comparator 2, and changes the lump level of overcurrent detection and the output current value of the inverter device 14. .

That is, when the voltage of the power source 10 for the gate current generator drops, the output current of the inverter device 14 and the overcurrent detection level are lowered depending on the degree of drop. Of course, when the power supply drops significantly, a method of stopping the operation of the inverter device 14 may also be implemented.

As described above, according to this embodiment, the current controlled by the GTO element is changed according to the state of the gate current of the GTO element, and therefore, there is an effect of preventing damage to the GTO element due to insufficient gate current.

This is particularly effective for devices where the power source of the gate current generator is unstable, such as devices for trains.

〔Effect of the invention〕

According to the present invention, in order to change the current controlled by the element in accordance with a decrease in the power supply voltage of the gate current generator of the self-extinguishing switching element, it is necessary to make the power supply of the gate current generator constant voltage. Therefore, it is possible to reduce the size of the device and improve its reliability.

[Brief explanation of the drawing]

Fig. 1 is a control block diagram of an embodiment of the present invention, Fig. 2 is a gate current waveform diagram, Fig. 3 is a gate current generation circuit diagram, and Fig. 4 is a block diagram of a part of conventional current control. .

Claims (1)

[Claims] 1. A self-extinguishing switching element, and a device for controlling the switching current of the self-extinguishing switching element;
A power conversion device comprising a power source and a device for driving the gate of the self-arc-extinguishing switching element, comprising a device that detects the voltage of the power source for driving the gate and changes the current controlled by the self-arc-extinguishing switching element. A protection device for a self-extinguishing switching element, characterized in that: 2. The protection device for a self-arc-extinguishing switching element according to claim 1, wherein the self-arc-extinguishing switching element is a gate turn-off or a thyristor.