JPS62100163A - Protective device for gate turn-off thyristor - Google Patents

Abstract

PURPOSE:To protect a gate turn-OFF thyristor (GTO) from overcurrents without depending upon the fusing of a fuse, etc. by conducting gate turn-OFF by OFF pulses when the value of abnormal currents on a short-circuit failure, etc. extends over the controllable anode current value or less of the GTO even on abnormal currents. CONSTITUTION:When the anode currents of a GTO 11 abnormally increase and a current detector 31 outputs an abnormal-current decision signal, a gate control section 51 outputs an OFF-pulse generating signal to a gate pulse generator 41 for the GTO 11, the gate pulse generator 41 conducts the OFF pulses of the GTO 11 of abnormal currents, the GTO 11 is turned OFF after a certain time passes, and abnormal currents are interrupted. When anode currents after a certain time passes do not reach zero, ON pulses are conducted through GTOs 11-16 for an inverter section, the GTOs 11-16 are turned-OFF simultaneously, and abnormal currents are shunted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a protection device for a gate turn-off thyristor.

[Conventional technology]

Gate turn-off thyristor (hereinafter referred to as GTO).

) is a three-terminal P with anode, cathode and gate
By passing a positive gate current (hereinafter referred to as an on-pulse) between the gate and cathode in a semiconductor element having a four-layer NPN structure, the device is turned on, and a negative gate current (hereinafter referred to as an off-pulse) is passed between the gate and cathode. It has the property of turning off when current is passed through it, and in recent years it has been actively applied to various circuits. In general, compared to thyristors, GTOs do not require commutation circuits and are capable of high-speed switching, so they have the advantage of simplifying the system itself and achieving high-speed response. On the other hand, for example, if a current exceeding the controllable anode current value of the GTO is turned off at the gate, there is a high possibility that the GTO will be permanently destroyed and a serious accident will occur, such as making it impossible for the system itself to continue operating. . For this reason, the anode current of the GTO is monitored, and if the anode current of the GTO exceeds the controllable anode current value due to a short circuit accident, etc., in order to prevent permanent destruction of the GTO due to failure in turn-off.
It is common to prohibit the flow of off-pulses and cut off overcurrent using a current limiting fuse or the like.

[Problem that the invention seeks to solve]

However, since GTO has the characteristic of being able to cut off the anode current with an off-pulse, even if there is an abnormal current such as in the event of a short circuit, if the value is less than the controllable anode current value of the GTO, the gate can be turned off using an off-pulse. Therefore, protection from overcurrent can be achieved without the need for fuse blowouts or the like.

An object of the present invention is to provide a GTO protection device that can prevent permanent destruction of the GTO by utilizing the gate turn-off characteristics of the GTO.

[Means for solving problems]

A feature of the present invention is that when the anode current of the GTO becomes abnormal, an off pulse is passed through the GTO to turn off the GTO, and if the anode current does not become zero after a certain period of time, the system multiple Gs of
The point is that an on-pulse is passed through the TO to shunt the overcurrent.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 shows the circuit configuration of an embodiment of the present invention, and FIG. 2 shows its time chart.

Figure 1 shows the case where this embodiment is applied to an inverter.
In FIG. 1, a series body of a reactor 3, a current limiting fuse 4, an inverter control section 61, and a smoothing capacitor 2 are connected in parallel with a DC power supply 1. Inverter control section 61 and induction motor 5 are connected. Inverter control section 61
Freewheeling diodes 21 to 26 are connected in antiparallel to each of GTO11 to 16 and GTOII to 16, and GTOII to GTOII to
Current detectors 31 to 36 are connected to each of the 16 anodes. Gate pulse generators 41 to 46 are connected between the gate cathodes of each of GTO II to 16, and the gate pulse generators 41 to 46 are controlled by a gate control section 51. In addition, the gate control section 51 and the current detector 3
1 is connected.

The GTOs 11 to 16 are turned on and off by the outputs of the gate pulse generators 41 to 46 controlled by the gate control section 51, and supply AC power to the induction motor 5. Current detector 31
~36 is GTOII~16 anode current is GTOI
An abnormal current determination signal is output to the gate control section 51 when the determination value set in consideration of the controllable anode currents I to 16 is exceeded. Here, consider a case where, for example, the anode current of GTQll increases abnormally and the current detector 31 outputs an abnormal current determination signal. The gate control unit 51 is connected to the GT connected to the current detector 31 that has generated the abnormal current determination signal.
An off-pulse generation signal is output to the gate pulse generator 41 of the OII, and the gate pulse generator 41 detects the abnormal current in the GTO.
II off-pulse is applied, and after a certain period of time, GTOI
I turns off and cuts off the abnormal current. FIG. 2 shows this operation.

However, if the off-pulse cannot flow due to an abnormality in the gate pulse generator 41 or the like, protection to cut off the abnormal current may not be possible.

The operation in this case will be explained using FIG.

If the off-pulse is not passed due to the gate pulse generator 41 or the like, the abnormal anode current of the GTOII will further increase because the GTOII will not be turned off.

In this case, protection is provided by blowing out the current limiting fuse 4, but if the rate of increase in abnormal current is large, it is often difficult to select a current limiting fuse 4 that can coordinate protection with the overcurrent withstand capacity of the GT○ element. Therefore, if the abnormal current cannot be cut off by gate turn-off, it is necessary to suppress the rate of increase of the abnormal current by some method to facilitate protection coordination with the current limiting fuse 4. For the purpose of such current suppression, an on-pulse is passed through GT011-16 of the inverter section to turn on GTO11-16 all at once.
Diverts abnormal current.

In addition, to detect failure of protection due to gate turn-off, compare the generation time of the abnormal current judgment signal output by the current detector 31 and the preset time, taking into consideration the delay time of the circuit and GTO. 6, which can be realized by doing.

When the abnormal current cannot be cut off due to gate turn-off, the fact that the output time of the abnormal current determination signal from the current detector 31 is longer than the completion time is utilized. In such a case, the gate control section 51 controls the gate pulse generators 41 to 46.
An on-pulse generation signal is output to turn off the GTOs 11 to 16 all at once, and the abnormal current is shunted. The GTO is then protected from abnormal current by blowing out the current limiting fuse 4.

As described above, according to this embodiment, even if the anode current of the GTO becomes abnormal, the abnormal current is not cut off by gate turn-off in the region where the anode current is small, without causing a fuse blowout, etc. If the gate cannot be turned off, the abnormal current is shunted to multiple GTOs to reliably prevent permanent damage to the GTO, and to ensure coordination of protection between the current limiting fuse and the overcurrent withstand capacity of the GTO. can be facilitated.

Note that in the above description, the anode current of each GTO is individually monitored, but the anode current may be monitored using the total of a plurality of anode currents that constitute the system.

In addition, although the above description is based on the case where this embodiment is applied to an inverter circuit, it goes without saying that it can be applied to other systems such as a converter using a GTO. It may also be a semiconductor element.

〔Effect of the invention〕

According to the present invention, there are the following effects.

(1) Permanent destruction of expensive GTO can be prevented.

(2) The effect of (1) significantly improves the reliability of the entire system or the operational stability.

[Brief explanation of drawings]

FIG. 1 is a protection circuit diagram of a gate turn-off thyristor according to an embodiment of the present invention, and FIGS. 2 and 3 are time charts showing its operation. 11-16...Gate turn-off thyristor, 21-
26... Freewheeling diode, 31-36... Current detector, 41-46... Gate pulse generator, 51...
Gate control section.

Claims (1)

[Claims] 1. In protecting a plurality of gate turn-off thyristors, the anode current value of the gate turn-off thyristor is monitored, and after the value exceeds a predetermined value, the gate turn-off thyristor is An off-pulse is passed through the gate turn-off thyristor, and if the anode current does not become zero after a certain period of time after the anode current value exceeds a predetermined value, an on-pulse is passed through the gate turn-off thyristor to divert the overcurrent. A gate turn-off thyristor protection device characterized by: 2. A protection device for a gate turn-off thyristor according to claim 1, further comprising means for monitoring the anode current value as a sum of the anode current values of a plurality of gate turn-off thyristors.