JPS5893463A - Gate circuit for gate turn-off thyristor - Google Patents

Abstract

PURPOSE:To enable to break a large current at the abnormal time by constructing to enhance the negative applied voltage of a gate circuit only when large breaking current due to occurrence of an abnormality is necessary. CONSTITUTION:When an abnormal current is flowed in a shortcircuited load or the like, thereby necessitating an emergency breakage, the breaking current of a gate off thyristor (GTO) 3 also becomes large. Accordingly, a switch 9 is contacted at the side b, thereby allowing the GTO 3 to be interrupted by the negative current applied voltage Ed3, which is the same as the case that the GTO 3 is turned OFF by a DC voltage Ed2, and large breaking current can be consequently interrupted. After the emergency breakage of the GTO 3, the switch 9 is automatically switched to the side a for a short period of time. Therefore, the voltage Ed3 can be set to a voltage higher than the avalanche voltage of -VGK of the GTO 3, thereby effectively breaking the large current of the GTO 3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gate circuit for a gate turn-off thyristor (G'j'0), and relates to a gate circuit that allows a large breaking current to flow through b and * when turned off.

Generally, when GTO is used in the inverter (9) path, the steady current is used within a controllable current range, but for example, when the inverter load is short-circuited, it is necessary to make the current limiting reactor as small as possible. The maximum breaking current of is required to be as large as possible. However, the maximum breaking current of the GTO is determined by external factors once the pellet structure of the device is determined. External factors include the snubber capacitor capacity and the amount of charge drawn out by the gate circuit.

However, in an inverter circuit, it is practically impossible to change the value of the snubber capacitor only when a large breaking current is required, such as when a load is short-circuited.

Therefore, the present invention focuses on the fact that it is possible to increase the amount of charge extracted by the gate circuit using current gate circuits instead of using electronic circuits. The purpose of this invention is to provide a gate circuit that can increase the negative applied voltage.

Figure 1 shows the basic circuit of the gate circuit. Step-down transformer 1
The voltage stepped down by the rectifier circuit 2 is rectified to form a DC voltage E-dr1. - Edt is created.・So,
Since V, , and Vt of the step-down transer 1 are set to the same voltage value, Eds = Ed. Edll Ed.

Since the -Voi guaranteed value of the GTO element is 13V, the voltage is generally designed to be 12V. This is the p:goff voltage when Ed2 turns off GTO3, but this Ego
The relationship between ff and maximum breaking current is as shown in FIG. 6. It has been confirmed that the larger Ego[f, the larger the maximum breaking current IM. In order to handle such data, we devised the circuit of the present invention as shown in FIG.

To explain the operation, first, the step-down transformer 1 steps down the secondary voltage, and at this time, the turns ratio of the step-down transformer secondary winding is changed so that Vt<v2. Rectified DC voltage Edl <
EdB and Ed2 are voltage-divided by a capacitor 6.7 and divided into Ed2 and Ed+.

At this time, by setting Ed, = Ed, the control circuit 8 applies the same voltage as in FIG. 1 and performs the same operation.

When the GTo3 is in a steady operating state, the switch 9 is in contact with the contact a side, and functions exactly the same as the basic circuit shown in FIG. 1. GT
FIG. 4 shows the flow of negative gate current when O3 is off. If abnormal current flows due to load short circuit etc. and emergency shutoff is required, use GT.
Since the cutoff current of o3 also increases, the switch 9 is brought into contact with the b side and GTo3 is cut off with the voltage of Ed, pEgo.
Since this is the same as when ff is high, it is possible to interrupt even a large interrupting current. FIG. 5 shows the flow of negative gate current when GTO3 is off. The switch 9 is constructed of an electronic circuit as shown in FIG. 3, and is capable of following short-time operations. ,
In addition to transistors, thyristors can also be used as switching elements. Further, the terminal 10 is an emergency cutoff command input terminal. By making the input signal short, for example, about 100 μs, the switch 9 is automatically switched to the a side after the GTO is cut off in an emergency, so a voltage of 13 V or more is applied to the -Vo of the element for a long time. Since it is a short-time operation, it is possible to set Eda higher than the -Vax avalanche voltage of GTo3, and it is possible to reliably cut off the large current of GTo3.

FIG. 7 shows an example in which the present invention is applied to an actual inverter. In an actual inverter, during emergency shutoff, the N side G as shown in the figure
Just turn off T03.<Turn the GTO gate circuit power supply to 1.
Since the switch 9 can be made into multiple switches, only one switch 9 is required, and a large current can be cut off reliably with a simple circuit configuration.

The present invention has the advantage of being able to cut off a large current in the event of an abnormality, making it possible to reduce the constant value of the current limiting reactor of the device, and making it possible to downsize the device.

[Brief explanation of the drawing]

Fig. 1 is a basic circuit of a gate circuit for GTO, Fig. 2 is an embodiment of a gate circuit according to the present invention, Fig. 3 is an example of an electronic circuit of a switch section, Fig. 4 is a path diagram of off-state current in steady state, FIG. 5 is a path diagram of off-state current during abnormality, FIG. 6 is a diagram showing the relationship between p:goff and maximum cut-off current IM, and FIG. 7 is a diagram showing an example of a circuit mounted in an inverter circuit. 1... Step-down transformer, 2... Rectifying element, 3... G
To. 4... Capacitor for ON, 5... Capacitor for OFF, 6... Capacitor for OFF, 7... Capacitor for OFF, 8... Control circuit, 9... Selector switch, 10...
...Detection terminal, 11...Turn-on transistor, 12.
...LG. 13... Thyristor for off, 14... Switch control time 1st colloquialism 21D Me 4 Lower f15 Edict Y Otsu I loff

Claims (1)

[Claims] 1. In the gate circuit of the gate turn-off thyristor, in order to reliably cut off the excessive current flowing to the gate turn-off thyristor due to a load short-circuit of the device, etc., a power supply section and a changeover switch are installed to increase the voltage for turning off in the event of an abnormality. A gate circuit for a gate turn-off thyristor characterized by the following.