SU1621113A2 - Overcurrent and shorting protection device for three-phase loads - Google Patents

Abstract

The invention relates to electrical engineering. The purpose of the invention is to increase reliability by limiting switching overvoltages when disconnecting an inductive load. The introduction of three key ele

Description

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Copies 18-20, a pulse transformer 13 and a differentiating chain 12 with corresponding connections provide a short circuit for the current arising under the action of the EMF self-induction (the invention relates to electrical engineering and can be used mainly to power general-purpose radio electronic equipment.

The aim of the invention is to increase reliability by limiting switching overvoltages when disconnecting an inductive load.

Fig, 1 shows a functional diagram of the device; figure 2 -diagram work.

The device for protection against current overloads and short circuits of three-phase loads contains a three-phase power transformer 1, a three-phase rectifier 2, a protective switching unit 3, an indicator unit 4, the first galvanic isolation unit 5, a matching unit 6 with a threshold element, a control unit 7, a second galvanic isolation unit 8, remote control-9 with switching 10 and indicator 11, differentiating chain 12, pulse transformer 13 with primary winding 14 and secondary windings 15-17, three key elements 1 8-20, each of which contains transistors 21 and 22 and diodes 23 and 24, in addition, the device contains a load 25.

The device works as follows.

If a current overload occurs at the time ti, the load current h by the time t2 exceeds the specified maximum permissible value. In, is triggered protective switching unit 3 (figure 2, a). At the same time, the voltage drop Ez on the block 3 sharply increases (Fig. 2, b), when triggered in the windings of the transformer 1, a self-induced EMF difference occurs, which through the diodes of the rectifier 2 is applied to the differentiating chain 12 with a positive polarity. This voltage difference Ei2 is differentiated by the chain 12 and through the windings 14-17 of the pulse transformer 13 is fed to the control inputs of the key elements 18-17 as a positive pulse. This provides

power transformer

1 when the protection switching unit 3 is triggered. As a result, switching overvoltages are eliminated.

2il.

unlocking transistors 21 and 22 key elements 15-17. They shunt the primary windings of the power transformer 1, as a result of which the short-circuiting of the circuits for current flow under the action of self-induced EMF is achieved. This eliminates the possibility of switching overvoltages on unit 3 and on load 25 if it has an inductive response.

After the current overload ceases at time ta, the protection switching unit 3 returns to its initial closed state, as a result of which the primary windings of the transformer 1 are closed again. In this case, the voltage drop on unit 3 vanishes and the differentiating chain 12 is applied in this way negative voltage drop. This differential after differentiation in the chain 12 is transmitted through the transformer 13 to the control inputs of the key elements 18-20 in the form of a negative pulse. This provides a forced locking of the transistors 21 and 22 and the aforementioned key elements.

Claims (1)

The invention The device for protection against current overloads and short circuits of three-phase loads on auth.St. Isfc 1181037, characterized in that, in order to increase reliability by limiting switching overvoltages when disconnecting an inductive load, it additionally introduces a differentiating circuit, a pulse transformer primary and three secondary windings, three key elements, while a differentiating circuit is connected parallel to the output of the rectifier , to the output of which the primary winding of the pulse transformer is connected, is connected in accordance with the secondary windings, each of which is connected to a control input with the corresponding key element, the outputs of each of which are intended for parallel connection of the corresponding primary winding of the transformer. one but t, tt t, J / F : “J five i f No. t