SU881888A1 - Device for arcles switching of ac circuits - Google Patents

Description

one

The invention relates to electrical engineering, in particular to electrical appliances.

A device for fast-arc switching of alternating current circuits is known, which contains power contacts and a shunt circuit of two oppositely connected thyristors 1.

The closest in technical essence and the achieved result is a device for arc-free switching of alternating current circuits containing a choke connected in series with the power contacts and a shunt contact circuit consisting of two parallel-connected thyristors 2.

The disadvantage of these devices is their low reliability.

The purpose of the invention is to increase the reliability of the device.

The goal is achieved by the fact that the device is equipped with a resistance connected to the shunt circuit in series with one of the thyristors.

FIG. 1 shows a diagram of the device; in fig. 2 is a diagram of current and induction in a reactor; the first is a high drop thyristor.

stress; in fig. 3 - the same, the thyristor is switched on first with a smaller voltage drop.

The device consists of a contact I, a reactor 2 connected in series and a shunt circuit 3 consisting of anti-parallel thyristors 4 and 5, in series with one of which includes a resistance, the role of which can be performed either by diode b or by a resistor.

The device is connected to the electrical network through clamps 7 and 8.

In the switched on position of the device (Fig. 1), contact 1 is closed, current flows through it and reactor 2, which each half-period reloads under the action of the supply voltage. When a trip command is applied, the control pulses are applied to the thyristors 4 and 5, thereby causing the shunt chain 3 to pass to the drive state. When the current passes through zero (time t, figs. 2 and 3), reactor 2 begins to re-magnetize under the action of the source voltage, a voltage appears at the reactor.2, under the action of which the current

switches to the shunt circuit 3 and depending on the polarity of the voltage on the terminals 7 and 8. flows through the thyristor 4 or the thyristor 5, after which the contact is de-energized. Let the polarity of the voltage at terminals 7 and 8 be such that the current of the thyristor 4 begins to flow. Under the action of the voltage drop across the thyristor 4, the reactor 2 is re-magnetized. Reactor 2 is selected so that by the end of the half-period it is re-magnetized by an amount less than double residual induction, therefore the contact is half-free all the time. Therefore, the thyristor 4 is closed and the thyristor 5 is opened. Reactor 2 begins to reversal under the effect of voltage drop on thyristor 5 in the direction opposite to the direction of magnetization reversal under the action of voltage drop on thyristor 4. Then two consecutive Depending on whether the voltage drop on thyristor 5 is greater than that on thyristor 4, or less, if the voltage drop on thyristor 5 is less than the voltage drop on thyristor 4, then by the end of the second half period (Fig. 2) the reactor 2. Remagnetized by a smaller value than in the first half-period, does not reach saturation and the contacts remain de-energized during the first and second half-periods. When the current passes through zero, the polarity of the terminals 7 and 8 changes, the thyristor 4 opens, the thyristor 5 closes and starting new cycle with magnetization reversal, but in each successive cycle of reactor 2 peremagnichivaets stronger than the previous. This process continues until, in the next cycle (time tn in Fig. 2), the induction in reactor 2 does not exceed the residual induction values. All this time (t-tn) contacts remain de-energized. The difference in the voltage drop in thyristors 4 and 5 is achieved by switching on resistance (diode 6 or a resistor). After breaking

contact 1, the current flows through the shunt circuit 3 and after the control pulses are removed from thyristors 4 and 5, the current is disconnected by the shunting circuit 3. The second half period (tg in FIG. 3), or towards its end, the reactor 2 is saturated and the current begins to flow through the contacts 1 until the beginning of the third half period, after which the cycle repeats. The opening of contact 1 can be started from the moment of time t (Fig. 3) and should be completed by the time tj (Fig. 3), then the opening of contact 1 occurs without the formation of an arc. If the polarity of the voltage at terminals 7 and 8 is such that current flows through the thyristor 5, the nature of the process and the principle of operation do not change. As a result, good conditions are created for the arcless opening of contact 1, which can be started from the time t and must be completed by the time t c.

The proposed device favorably differs from the known one, since it is more reliable and also has smaller dimensions and weight.

Claims (2)

1. USSR author's certificate number 292267, cl. H 01 H 9/54, 1967. 2. Author's certificate. USSR on application 2562122 / 24-07, cl. H 01 H 9/30, 1978. 7 fw.f