SU922902A1 - Vacuum arc blow-out chamber vacuum arc blow-out chamber with double breaking - Google Patents

Description

The invention relates to electrical engineering, namely to vacuum switching devices.

Known designs of vacuum 5

arcing chambers (VDK) with double break, consisting of a shell of one movable, fixed and intermediate contacts. The presence of a double break provides an increase in voltage, switching capacity and wear resistance of VDK [1] and [2}.

The disadvantage of these VDK - the need for synchronous opening of contacts. In this case, the opening arc occurs in two gaps, which contributes to a decrease in the arc burning time, an increase in the limiting switching capacity and wear resistance. ·, · ΖΙ)

In the case of an asynchronous shutdown, the arc that occurred in the first discontinuity may have time to go out before the second rupture occurs.

In this case the different contacts of the first discontinuity ^ 5 will be subjected to severe destruction, ^ζ which may lead to nerabotosposdbnosti WEC.

The closest in technical essence to the present invention is 30

2

A device is a device in which an intermediate contact is connected to a bellows, which allows it to reciprocate. Bellows fortified. On the screen, which protects the dielectric part of the shell VDK from contact erosion products. When switched on, the first to be closed without current is a moving contact with an intermediate contact, and then an intermediate contact with a fixed contact. Consequently, the last pair of contacts perceives the effect of a short circuit arc, the energy of which can be especially great when the VDK switches on at the moment of short circuit [3].

However, this pair of contacts can also be strongly affected by the opening arc, if the non-synchronization of the contact opening is commensurate with the time of the opening arc. To reduce this non-synchronization, it is necessary to increase the speed of opening of the moving contact, and this causes certain difficulties in designing a switching device with such VDK.

3

922902

four

In addition, the well-known VDK has the inability to switch small currents without the appearance of significant switching overvoltages exceeding the electrical strength of the insulation of low-voltage electrical equipment. This is due to the fact that their contacts are made of a material with a high cutoff current. ·

The purpose of the invention is to reduce switching voltage to values that are not dangerous for isolating low-voltage electrical equipment.

This goal is achieved by the fact that in a VDK with a double break, the fixed contact and the part 5 of the intermediate contact facing it are made of a material ₍ different from the material of the moving contact and the part of the intermediate contact facing it, and the gap between the moving and intermediate contacts is no less 1.2 times more than the contact gap between the fixed and intermediate contacts.

The stationary contact and the part of the intermediate contact facing it can be made of a material with high electrical conductivity] arc resistance and resistance to welding, for example, metal-ceramic tungsten impregnated with a copper-bismuth alloy.

The movable contact and the part of the intermediate contact facing it are made of a material with a low cut-off current, for example, molybdenum, containing an alloy based on antimony.

In addition, the fixed and intermediate contacts can have an additional electrical connection in the form of a resistor, the resistance of which is not less than 1.5 times higher than the contact resistance of these contacts.

The use of dissimilar materials 45 contacts allows you to stabilize the limiting switching capacity and wear resistance when switching short-circuit currents and significantly reduce overvoltage to values not dangerous for electrical equipment insulation when switching small currents. The latter is achieved by using materials with a low cut-off current, and the first two parameters — by using highly electrically conductive, arc-resistant, and welding-resistant materials.

20

25

thirty

50

55

In the case of the use of an additional electrical connection with a resistor between the fixed and intermediate contacts, the requirement of synchronous opening of the VDK contacts with two breaks is completely eliminated. 65

FIG. 1 shows a VDC section with two breaks a and b, movable 1, intermediate 2 and fixed 2 contacts and sheath 4; in fig. 2 - section VDK with. two breaks a, b and an additional electrical connection 5 with a resistor 6 between the fixed 3 and intermediate

2 pins.

VDK with two breaks works as follows.

When turned on, contacts 1 and 2 of the gap a first close, and then contacts 2 and 3 of the gap b. Since the last manufacturing contacts are made of a material with high electrical conductivity and resistance to welding, there is no significant destruction and strong welding of contacts 2 and 3 even when they are closed at the moment of short circuit. If, however, a resistor is connected between contacts ** 2 and 3, a short-circuit arc occurs between contacts 1 and 2. Since the resistor limits the current of the power circuit, there is also no significant destruction of contacts 1 and 2 when they close at the moment of short circuit. '

When VDK is disconnected, pins 2 and 3 and 1 and 2 open either simultaneously, i.e. synchronously or non-simultaneously (asynchronously). When synchronous opening of contacts occurs, the greatest instability of the arc between contacts 2 and 3 takes place, but since the distance between them is small, due to overvoltages, there is a breakdown of this gap and the recurrence of the arc. In the future, the arc will go out between contacts 1 and 2 only at low currents, when overvoltage is already small, and the distance between the contacts is large.

If between pins 2 and

3 a resistor is turned on, the arc stability is ensured by the choice of the material of the contacts 1 and 2. Thus, the presence of contacts with a low cut-off current ensures the stability of the arc when small currents are turned off, and thus the reduction of the switching overvoltage to values not dangerous for the isolation of low-voltage electrical equipment is achieved.

The present invention can be used in vacuum switching devices for voltages up to 1140 V, which are subject to increased requirements for limiting switching capacity, switching overvoltage, developed by the institute VNIIelektroapparat. VDK with a double rupture, having a different 5.

922902

6

Native contacts, allows switching small currents without the occurrence of overvoltages dangerous to low-voltage electrical equipment and provides a stable high switching capacity and wear resistance.

Claims (4)

Claim 1. A double-gap vacuum interrupter chamber containing a shell, a screen, a moving and a fixed contact and an intermediate contact between them, in order to reduce the switching overvoltages, the fixed contact and the part of the intermediate contact facing it material other than the material of the movable contact and the part of the intermediate contact facing it, and the intercontact gap between the movable and intermediate contacts is no less than 1.2 times greater than the intercontact ny gap between the fixed and intermediate contacts. 2, the camera pop. 1, characterized by the fact that the fixed contact and the part of the intermediate contact facing it are made of a material with high electrical conductivity, arc resistance and resistance to welding, for example, metal-ceramic tungsten impregnated with a copper-bismuth alloy. 3. Camera pop. 1, characterized in that the movable contact and the part of intermediate contact contacting it are made of a material with a low cut current, for example, molybdenum, containing an alloy based on antimony. 4. Camera on π. 1, distinguishes 15 i am with that motionless and intermediate contacts are supplied with an additional electrical connection in the form of a resistor whose resistance is not less than 1.5 times higher 20 contact resistance of these contacts'.