SU978266A1 - Device for protecting converter from short circuiting currents in outer circuits - Google Patents

Description

(54) DEVICE FOR PROTECTION OF THE CONVERTER FROM SHORT CIRCUIT CURRENT INTO

: - WRONG CHAIN

one

The invention relates to a conversion technique and can be used to protect a converter of an anode circuit system of a bath of an electrolytic tinning unit and converters of a direct current electric drive.

There are known devices for protecting transducers containing current transformers, switching sensors, a pulse matching unit, an AND element, an output block, an organ blocking, an OR element, and a pulse selector with a duration of 1.

A disadvantage of the known devices is the low reliability due to the possibility of applying the current transformers.

The closest technical solution to the invention means and achieves: the result is a device for protection of the converter from short-circuit currents, containing an impulse - phase control unit, connected by its output to terminals for connecting control electrodes of pairwise counter-thyristors of the converter, trekhformatorny sensors thyristor current, the outputs of which are connected to the INPUT of the threshold element and the disconnecting relay, the contacts of which are included 5 in the power supply circuit of the G21 phase converter.

A disadvantage of the known device is low speed.

The goal of isophotenia is to act as a result of speed due to a reduced pause between the moment of the occurrence of a short circuit and the moment of the removal of thyristor control pulses.

The goal is achieved by the fact that the device is equipped with a memory element, an additional threshold element, a logic matching unit and a sensor for the rate of change of the load current output from the circuit through an additional threshold element to the first input of the matching unit, the second input of which is connected to the main threshold element and the output of the coincidence block is connected via a memory element to the control

the inputs of the shutdown relay and the unit of shunt-phase control.

The drawing shows a circuit diagram of a device for protecting a converter from short-circuit currents.

The device contains transformer current sensors 1, a threshold element 2, a logic block 3 coincidence, an element

4pami, relay 5 disconnecting, block 6 and pulse-phase control, terminals

for connecting the thyristors 7 of the pre-phaser, an additional threshold element 8, the sensor 9 of the rate of change of the alternating current current, an automatic switch 10 activated by a relay

5disable The converter also contains a transformer 11 and output terminals for connecting the load 12.

The device works as the next ofaz.

when the current transducer exceeds the specified value, a signal appears at the Second input of logic block 3. In the event of a short circuit, the voltage at the output of the sensor 9 of the rate of change of current 9 increases. When it exceeds a predetermined value, a signal appears at the first input of logic unit 3 of coincidence. The signal from the output of the logical block 3 of coincidence is fed to the input of element 4 of the shal-shti and is memorized by it. From one output of the memory element 4, the signal is fed to the input of the control unit 6., which ensures the removal of pulses from the control electrodes of the thyristors 7. The thyristors are closed and the supply voltage to the converter is stopped.

From the second output of block 4 of memory, the signal is fed to the input of relay 5 off, which ensures disconnection of the converter from the mains. The presence of memory block 4 ensures reliable operation of the relay 5 for switching off the block while reducing the rate of current rise during the development of a short circuit. The relay 5 to turn off the unit remains on until the signal is memorized. When power is removed from the device, the shutdown relay 5 is shut off. To put the protection device into operation, it is necessary to turn on the 1O circuit breaker and apply power to the protection device.

The use of the invention provides emergency shutdown of the circuit without exhaust and thyristors, and the high protection performance eliminates the operation of the fuses, which reduces the cost of restoring the device and eliminates the downtime associated with the replacement of damaged equipment.

Claims (2)

1. USSR Author's Certificate No. 838876, cl. And 02 H 7/10, 1979. 2. US Patent No. 359О323,: cl. H 02 H 7/12, 1976. tI fff