SU836719A2 - Device for protecting bridge thyristorized converter - Google Patents

Description

(54) DEVICE FOR PROTECTION OF THE BRIDGE TIRISTOR TRANSFORMER

I

The invention relates to the protection of converters.

According to the main author. St. No. 520661 is known a device for protecting a bridge thyristor converter from external and internal short circuits, which contains an e-bridge suppression circuit with two capacitors connected via isolating and switching valves between the terminals of the AC and DC current of the protected converter Lll. For the purpose of fairness by way of simplification, capacitors are connected in series with isolating diodes, the connection point of which is connected to the AC terminals of the converter through a choke.

The drawing shows a diagram of the proposed device.

The device consists of a power transformer 1, a rectifier made on thyristors 2-7, an extinguishing device made on

symmetrical triacs 8, 9, 10, limiting throttle 11, isolation diodes 12i, protective capacitors 13, input chokes 14, are included in the power supply circuit of the inverter 15 and uncontrolled valve 16, connected in parallel with the diodes and the choke 11.

The operation of the security device is as follows.

The protective capacitors 13 are charged through the diode 16 when the power is switched on the polarity indicated in the drawing. The inverter 15 starts only after charging the capacitors 13. With a short zakkayiya positive pitakitsoy {oyny on the ground emergency current flows through one of the thyristors of the cathode rectifier, for example through the thyristor 5. This current is mainly limited only by the choke .14. The emergency state sensor provides a signal for switching off the pulses.

control from the thyristor rectifier, and the inclusion of the maxistors 8, 9, 10.

In this case, the triac 8 is turned on and the oscillating discharge of the capacitor 13 occurs in the opposite direction of the emergency current. As a result, the thyristor 5 is locked, and the capacitor 13 is recharged along the circuit: input choke 14, short circuit one of the phases of the secondary winding of transformer 1, triac 8, right half of inductance 11, diode 12. As the charge current goes over, the current drops to zero and After the transition, the current through zero closes the diode 12 and the triac 8. Since the I2 diodes usually have significantly less turn-off time, switching them on to this circuit reduces the overvoltage that occurs on the triacs 8, 9, 10 when the current is interrupted.

In the case of a short circuit of the minuscuts on the ground, the operation of the device is similar, while the triacs 8, 9, 10 feed control pulses of the other polarity and they conduct current in the opposite direction. When the inverter 15 is inverted in turn, the disconnection is accomplished by locking the cathode or anode group of the thyristors above.

When thyristors are locked up

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and a current break through them on the inductance 11 causes a reverse voltage, which leads to the insertion of diode 16. Energy stored in one of the J half inductances 11 dissipates in the active resistance of the circuit consisting of diodes 12, 16 and the entire inductance 11.

10 The device allows to increase reliability, to completely eliminate the occurrence of dangerous reverse overvoltages on thyristor rectifiers.

Claims (1)

1. USSR author's certificate No. 520661, cl. H 02 H 7/10, 1975. -38OS / s w eight ztz Have / -II41PH L - A. / J / 0 fZ // w