SU540301A1 - Spark extinguisher - Google Patents

Description

(54) DEVICE FOR CLIPPING

one

The invention relates to electrical engineering and can be used in automation and remote control devices.

A spark suppressor device containing a relay, 1J diodes is known.

However, the use of spark-extinguishing devices with a diode is limited by the fact that there are no high-power high-frequency diodes, and in most cases the spark-extinguishing device operates with a relay that commits relatively high power, and the transient process that occurs after opening the contact parts proceeds from high by speed.

Closest to the invention is a spark suppression device, where a capacitor and a resistor connected in series are connected in parallel with the load (2j.

This makes it possible to reduce the erosion of the contacting surfaces when the contact parts open.

However, in such a device, contradictory requirements are imposed on the magnitude of the resistance. On the one hand, the magnitude must be as small as possible so that

after the contact parts were opened, the recoverable voltage U did not exceed the breakdown voltage U, i.e.

U

 7 U

(i)

Bn

etc

where T 0,5-0,8 - the safety factor

On the other hand, it must be large so that the sum of the load current Y | and the charge current of the capacitor 3 d-after closing the contact details did not exceed the maximum allowable value 3

max.dop (2)

Zar max-ext.

Ensuring that these two conditions are met is not always possible. Taking into account that the breakdown voltage immediately after opening the contact parts is determined by the voltage of a short arc, which for most contact materials is U, (8-10) V, and also that a critical or oscillatory mode is used for the spark damping, it is possible together expressions (1) and (2), determine the maximum load current C ("above

N M A KO "

conditions (1) and (2) are not simultaneously fulfilled:

(3)

Ki. Ao; t,

not

Ku

where is unp

E is the power supply voltage. It can be seen that the maximum load current, to which a turnip can work with a known spark-ignition device, is significantly less than the maximum allowable current, since m 0.5-0.8 and Ki 1.

Using relays with currents exceeding. Deg leads to a sharp decrease in reliability.

The purpose of the invention is to improve the reliability of the relay.

In the proposed device, this is achieved by shunting the resistor with an electronic switch made on the transistor and controlled synchronously with the relay. The drawing is a diagram of the proposed

devices.

In series with the contact details 1 of the relay, an inductive load 2 is connected, in parallel with which a capacitor 3 and a resistor 4 are connected in series.

In the initial state, before the supply of the control pulse, the contact parts 1 are open, the capacitor 3 is discharged, and there are no voltages on the electrodes of the transistor 5. With the arrival of a positive-polarity control pulse, a differentiated positive-polarity pulse arises at the base of transistor 5, which closes transistor 5 for the entire duration of the transient after closing contact parts 1. At the same time, the capacitor 3 is charged through 4 parts from the power source. The resistance value (resistor 4) is chosen such that during the entire transition time the sum of the capacitor charge current and load current does not exceed the maximum permissible value.

After the termination of the control pulse, a negative differentiated pulse appears at the base of transistor 5, which opens transistor 5 and transforms it into a saturated state. their opening.

5Communication of expressions (1)

and (2) for the proposed device in the most adverse conditions gives the maximum load current t), above which these conditions are simultaneously

not performed:

H

. (hMM

.Aon

eh max

The gain in the maximum load current at which it is still possible to use the relay with the spark-arrester device given by the proposed device is equal to;

Y N WQKC

Ki

) (five)

H

+ 1

and chg ku

and

With 11 0.8 and K U 2 the gain is equal. and when Ki 10 - 3.64, i.e. The application of the proposed device is especially advantageous for large values of K and. The indicated gain means that with the same load current with the proposed spark-extinguishing device a less powerful relay can be used than with a known device, while maintaining the same reliability, or using the same relay to obtain greater reliability. . ness All this leads to an economic gain.

Formulas

arr

and 3

et e and

A spark-ignition device containing a series of series-connected resistors and a capacitor connected in parallel to the load, a relay with a control coil, characterized in that, in order to increase reliability, it is additionally equipped with a capacitor and a transistor connected in parallel to the resistor, the base-emitter junction through which An additional capacitor is connected parallel to the relay control coil.

Sources of information taken into account in the examination:

1.Furmanov B. M, Scientific basis, methods of assessment. And ensuring the intrinsic safety of mining low-voltage electrical equipment. Science, 1970, p. 99-102, fig. 29.31.

2.Voronov A. A. To the calculation of spark-suppressing circuits for contacts operating

in the atmosphere. In the collection of articles on automation and electrical engineering, ed., Academy of Sciences of the USSR, 1956, (prototype)

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