SU838873A1 - Current protection device - Google Patents

Description

(54) CURRENT PROTECTION DEVICE

I

This invention relates to the protection of power supplies against short circuits and overcurrent during a slow rise of the monitored current.

A current protection device is known, which contains a constant voltage to pulse converter, a reference pulse generator, a shunt current sensor and an actuator 1.

However, the galvanic coupling between the monitored circuit and the protection circuit protects the high voltage power sources from short circuits and current overloads when the monitored current slowly increases.

The closest in technical essence and the achieved result to the invention is a current protection device containing a pulse transformer, the primary winding of which is connected to the controlled current circuit, and the secondary through a control unit is connected to the control electrode of the thyristor connected to the protection executive body 2.

A disadvantage of this device is its narrow functionality due to

the absence of regulation of the limits of protection with a slow increase in the controlled current.

The purpose of the invention is to expand the functionality.

The goal is achieved by the fact that the device is equipped with a pulse generator, an electronic key, a diode and a resistor, and the pulse transformer is supplied with an additional winding connected in opposite with the secondary winding, and the generator output is connected to the additional winding through an electronic key, and through the diode to the secondary winding of the transformer resistor-locked.

The drawing shows a block diagram of the device.

five

The device contains a current-sensitive circuit 1, including a pulse generator 2, an electronic switch 3, a decoupling diode 4 and a pulse voltage transformer 5, a terminating resistor 6, a control unit 7 O including a thyristor 8, an actuator 9 and a power supply 10 of the protection circuit.

The primary winding of the transformer 5. Is included in the controlled current circuit. One

from the ends of the secondary winding of the transformer 5 is connected to the input of the control unit 7, the output of which is connected to the control electrode of the thyristor 8, to the anode of which the actuator 9 is connected. The output of the generator 2 through the diode 4 is connected to the other end of the secondary winding of the transformer 5 and through the key 3 to additional winding, and these windings are included opposite. Parallel to the input of block 7 is included matching resistor 6.

The device works as follows.

The generator 2 generates pulses that arrive simultaneously at the input of the key 3 and through diode 4 to the secondary winding of the transformer 5. With the arrival of the pulse, the key 3 opens, and in the additional winding of the transformer 5 a current pulse is formed, which is transformed in antiphase into the secondary winding, as a result a voltage difference arises at resistor b. One of the latter comes from the generator 2 minus the voltage drop on diode 4, and the other occurs in the secondary winding of the transformer 5 when the switch 3 is closed. In the absence of a controlled current in the primary winding, the voltage on the resistor 6 is insufficient to turn on the control unit 7. When a controlled current flows through the primary winding, the core of the transformer is magnetized, as a result of which the voltage across the secondary winding decreases and increases at the resistor 6. At a certain current value, the voltage reaches a critical level, at which the control unit 7 switches on the thyristor 8, which outputs a signal to the actuator 9.

The use of this device allows to extend the functionality of the current protection by providing control of the protection limits with a slow increase of the controlled current. In addition, the exclusion of galvanic communication provides the ability to protect high-voltage power sources and increases the efficiency of the device, as well as creates conditions for unified current protection circuits, power sources.

Claims (2)

1. USSR Author's Certificate No. 353307, cl. H 02 H 3/08, 1968. 2.Silkin N.P., Smirnov A.V. Improving the effectiveness of relay protection of electronic devices. “Electronic equipment, series 1, -“ Electrical Engineering microwave, 1975, vol. 10, s. 91 -93.