JPS601778B2 - Gate circuit of gate turn-off thyristor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gate circuit for a gate turn-off thyristor (hereinafter abbreviated as GTO).

A GTO is a thyristor that can be turned on and off by gate control, and is known as a large current switching element.

The turn-off gain G of the GTO is expressed as G=11^/IGl. In this equation, IA is the rapidly breaking anode current, I
G is the gate current that flows when the battery is disconnected. Generally several hundred A
In a GTO that can cut off the above anode current, its turn-off gain G is about 2 to 5, and a gate current that is 1/2 to 1'5 of the anode current flows.
Therefore, the gate circuit needs to have a large capacity, and the overall size and power loss of the gate circuit are also large. Figure 1 shows a conventional GTO turn-off gate circuit.
1 is GT○, 1 2 is capacitor, 13 is thyristor,
14 is a voltage limiting circuit, and the area within the broken line in FIG. 1 is a gate circuit.

An anode current 1^ is currently flowing through the GTO II, and the capacitor 12 is charged with the voltage necessary for disconnection with the polarity shown. When the thyristor 13 is turned on here, the charging voltage of the capacitor 12 reverse biases the gate and cathode of the GTOI I. By applying a reverse bias between the gate and cathode, a part of the anode current of GTOI I flows through the gate to the syristor 13 and the capacitor 2.
A gate turn-off current IG flows through GTOI.
I will turn off. The relationship between the anode current 1^ and the gate circuit 1G is shown by the turn-off gain G of the GTO mentioned above, and in order to perform a good turn-off,
It is necessary to flow a sufficient gate current according to the anode current. Furthermore, when a GTO is used in a voltage-source inverter circuit or the like, normal load current and fault currents such as load short circuits and false firings should be taken into account as the anode current of the GTO.

These fault currents are numerically to several tens of times higher than the normal load current, and are undesirable currents for GT○ and devices. Therefore, it is important to prevent these fault currents from flowing as much as possible in order to minimize equipment accidents. One method is to detect a fault current and shut off the fault current using a GTO. However, a problem arises here. This is because, depending on the fault current, the anode current may rise several times as much as the anode current under normal load during the period between detecting the fault current and issuing a power cut command to the GTO. In other words, an anode current several times higher than that under normal load flows through the GTO, and the turn-off gate circuit requires a large-capacity gate circuit that can cut off this current. In a large-capacity gate circuit, the same amount of energy is consumed when cutting off the anode current under normal load as when cutting off the relatively large anode current during a fault, so the power loss is also large. This is economical and also increases the size of the entire gate circuit. As mentioned above, in the conventional example,
In order to minimize accidents, GTO was used to quickly cut off the fault current, but this required a large-capacity gate circuit, resulting in large power losses and a large gate circuit.

The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to
An object of the present invention is to provide a gate circuit for a GTO which prevents the circuit from becoming larger and from increasing power loss even when the fault current is cut off by an oscillator.

The present invention will be explained below based on examples.

In the configuration diagram showing an embodiment of the present invention, 15 and 16 are gate circuits, and terminals b and c are turn-off command input terminals for each gate circuit. Here, the gate circuit 15 is a gate circuit for shutting off during normal load, and the gate circuit 16 is a gate circuit for large current in case of an accident, etc. In normal operation, the gate circuit 15 is used to disconnect the anode of GTOI in response to a turn-off command from terminal a. Cut off the current. Also, 17 is a current transformer, 18 is a resistor, 19
is a current reference, and when the anode current of the GTO 1 1 increases in the event of an accident, the current reference 9 is also detected and amplified by the amplifier 201, and turned off to the terminal c of the gate circuit 16 for large current. GTOI by giving commands
The anode current of I is cut off. In this way, by providing a large current gate circuit 16 for accidents that occur only once or only rarely, no matter how large the current capacity is, the number of operations is small, so power loss can be reduced. There are almost none, and component ratings can be made smaller. In addition, the gate circuit 15 for normal load can be designed to the minimum that can cut off the anode current of the normal GTOI I, so the gate circuit as a whole will suffer from increased exposure loss and
Problems such as increasing the size can be prevented. Furthermore, the large current gate circuit 16 can be used as a backup, even though the number of operations is small, in case of turn-off failure when the normal load gate circuit 15 breaks down, improving the reliability of the gate circuit. be able to. In the present invention, any type of gate circuit may be used as the gate circuit 15 for normal load and the gate circuit 16 for large current during an accident, and the gate circuits 15 and 16 may be of different types. .

FIG. 3 shows an example of a gate circuit. Figure 3a
is the capacitor discharge type gate circuit shown in the conventional example, and the third
Figure b is an example of a gate circuit using a pulse transformer.
is a pulse transformer, 22 is a diode, 23 is a resistor, 2
4 is a DC power supply, 25 is a transistor, and 25 is a transistor.
In this method, a base current is applied to the transistor 5 to make it conductive, and a collector current flows therethrough, and the gate current is obtained by insulating the transistor 5 with a pulse transformer 21. As described above, in the present invention, GT
By separating the large current gate circuit, which cuts off the normal large current, and the normal load gate circuit, which cuts off the current that always flows through the GTO, using O, it is possible to prevent fault currents in the GTO. Even when the gate circuit is disconnected, it is possible to prevent the overall size of the gate circuit from increasing in size and power loss, and to provide a highly reliable GTO gate circuit.

[Brief explanation of drawings]

FIG. 1 is a conventional GTO gate circuit, FIG. 2 is a configuration diagram showing an embodiment of the GTO gate circuit according to the present invention, and FIG. 3 is a circuit showing a specific example of the gate circuit in FIG. 2. It is a diagram. 1 1; Gate turn-off thyristor (GTO), 12
; Capacitor, 13: Siris filter, 14; Voltage limiting circuit, 15, 16: Gate circuit, 17: Current transformer, 18, 23
;Resistor, 19: Current reference, 20; Amplifier, 21: Pulse transformer, 22; Diode, 24; DC power supply, 25;
transistor. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1 For one gate turn-off thyristor, there is an off-gate circuit for normal load that responds to the gate command signal issued during normal operation and is used in a region with relatively small shear current, and an off-gate circuit for normal load that responds to the fault current detection signal. A gate circuit for a gate turn-off thyristor characterized by comprising two off-gate circuits, a large-current off-gate circuit used for cutting off large currents.