SU1345284A1 - Apparatus for protecting three-phase electric units - Google Patents

Abstract

The invention relates to electrical engineering, in particular to the protection and automation of semiconductor converters and motors. The aim of the invention is to increase the reliability with a non-sinusoidal form of the supply current. The device works as follows. In the symmetric mode of power supply of the protected electrical installation, current pulses occur in the windings of the cores located around the current-carrying wires of the phases, which arrive at the control windings of the magnetic core. In this case, in its output winding, opposite-polarized pulses appear, which arrive at the pulse selector. The pulse selector matches them in duration and does not generate a signal to turn off the electrical installation. When one of the phases breaks, one of the cores, located around the current-carrying wires of the phases, is saturated with unipolar current pulses. As a result, no pulses are generated in the output winding of the magnetic core. The pulse selector generates a trip signal. 1 il. but (/)

Description

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The invention relates to electrical engineering and can be used in devices for the protection and automation of semiconductor energy converters and in devices for the protection of electric motors.

The aim of the invention is to increase the reliability of its action in the non-sinusoidal form of the supply current of the protected electrical installation.

FIG. 1 shows a functional diagram of the proposed device; in fig. 2 - graphs that show the work of its nodes.

The device contains the first magnetic core 1 with a rectangular hysteresis loop with two windings 2 and 3, the second and third cores 4 and 5 with a rectangular hysteresis loop, with the beginning of the winding 6 through diode 7 connected to the end of the control winding 2, and the beginning of the control winding 3 through the diode 8 - to the end of the winding 9. To the output winding 10 located on the core 1, a pulse selector 11 is connected.

The device works as follows.

In the symmetric mode of power supply of the protected electrical installation in windings 6 and 9 on cores 4 and 5 with current hysteresis loop located around current-carrying wires of phases A and C or their parts, current pulses appear, which through diodes 7 and 8 arrive at control windings 2 and 3 magnetic cores 1. As a result of the sequential connection of the windings 6, 2 and 9, 3 and the multidirectional series connection of the diodes 7 and 8 in these circuits, current pulses of different polarity are formed (Fig. 2). In a symmetric mode of operation Installation on the input of the pulse selector 11 pulses of a certain duration arrive at intervals of time depending on the frequency of the power supply network. The pulse selector matches the pulses according to their duration and does not produce a signal to turn off the protected electrical installation.

When one of the phases A or C is broken, the magnitude of the primary current, which remagnetizes the core 4 or 5 with the square hysteresis loop, takes a zero value. At the same time, one of the cores 4 or 5 is

It is supplied with unipolar current pulses. As a result, no pulses are generated in the output winding 10. Pulse selector 11 generates a signal to turn off the protected electrical installation. I

In the event of a phase break in the winding B (not shown), in which a core with a rectangular hysteresis loop is not installed, the API, in a two-phase short circuit between phases A and B, the current vectors of phases A and B have opposite directions. The current pulses supplied to the control windings 2 and 3 of the magnetic core 1 have approximately the same amplitude values. The resulting magnetic flux generated by these pulses is close to zero. The pulse selector generates a signal to disable the protected electrical installation or to activate the alarm.

The technical and economic efficiency of the proposed device consists in increasing the reliability by ensuring the protection of electrical installations from all types of asymmetrical modes of operation. Distortion of the primary current form does not disrupt the formation of pulses. In general, the device is simplified due to the decrease in

the number of items used. I

Claims (1)

Invention Formula A device for protection of three-phase electrical installations from asymmetrical operating modes, comprising a magnetic core with first and second control windings and an output winding connected to a pulse selector, characterized in that, in order to improve the reliability of a non-sinusoidal supply current, two magnetic cores are added to it with windings through which the conductive wires of the two phases or their part feed the electrical installation, with the end of the output winding of the first magnetic core discharge phase is connected through the diode raspolozhennsh anode to the output winding of the core-sequentially according to the first control winding and the start vyhod3134528 i winding the second magnetic ser- to the output winding of the second core of the other phase of the other phase is connected through another diode located by the cathode ka, according to, consistently with the second control winding. ka, according to, consistently with the second control winding. FI.1 fiv.2 Editor A. Lezhnin Compiled by, Zimakov Tehred A. Kravchuk Proofreader M. Maksimishinets Order 4928/52 Circulation 617 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, Projecto st., 4