CS238999B1 - Electrical contact for contact switching devices - Google Patents

Abstract

An electrical contact for contact switching devices, consisting of a contact body and an extinguishing insert, the material of which is at least partly from the group of oxides, sulfides, carbides, nitrides, borides or phosphides of metals and whose ionization voltage is higher than the ionization voltage of the material of the contact body. This results in an increase in the service life of the contact system.

Description

BACKGROUND OF THE INVENTION The present invention relates to an electrical contact for contact switching devices, comprising a contact body and a quencher.

The lifetime of the contact switchgear is largely determined by the lifetime of their contacts. Achieving a low vapor contact of the contact material under the influence of an arc, i.e. a high contact life, is difficult because good contact has to meet other requirements, in particular a low contact resistance in the closed state. In the case of one-component contact materials, the low contact resistance and the long service life are at the same time impossible to achieve. Although multi-component contact materials such as AgCdO can be improved, it is always a compromise still acceptable in terms of both properties. The problem can be solved by dividing the function into two contacts, the main ones with good electrical conductivity and tanning ones with higher resistance to arc burning. This solution, however, significantly complicates and makes the device more expensive. It is also known to provide contacts with a tanning insert, wherein the on-contact contact provides a base contact material with good electrical conductivity, e.g. After opening the contacts, the heel of the resulting arc is placed on a tanning insert made of a material more resistant to the burning of the arc, such as tungsten. In all these solutions, the electrical contact remains a passive element with respect to the arc burning, since arc extinguishing is achieved by means independent of the contact, e.g.

The described disadvantages are eliminated by the electrical contact according to the invention, consisting of the contact body and the quencher.

The essence of the invention is that the quencher material is at least partially selected from the group of oxides, carbides, nitrides, borides, or metal phosphides, and that its ionic stress is higher than the ionic stress of the contact body material.

238 999

The electrical contact according to the invention is particularly advantageous in that the quenching insert material affects the stability of the arc burning and increases its tendency to prematurely go out. This achieves an increase in the service life of both the contact itself and the switchgear in which the contact is built-in.

Embodiments of the electrical contact according to the invention are schematically illustrated in the accompanying drawings.

Fig. 1 is a cross-sectional view of a contact with an annuloid quencher and a permanent magnet. Fig. 2 is a view of an inch-type contact.

In the first exemplary embodiment (FIG. 1), the cylindrical electrical contact 10 with the slightly convex contact surface 101 is formed by a contact body 11 of good electrical conductivity, e.g. copper, and a flame-retardant insert 21 of ZnO, a material whose ionizing voltage is higher than that of the material of the contact body 11. The contact body 11 and the quencher 21 are mechanically rigidly and electrically conductively connected together. A permanent magnet 31 is inserted into the contact body 11. In the drawing (FIG. 1), the positions of the arc are plotted so that the arc at the time of its formation is indicated by 41, the arc at the time of its extinguishing is indicated by 42.

A second embodiment of the electrical contact according to the invention (FIG. 2) is a thumb-shaped contact. A quenching insert 22 is inserted into the contact body 12.

The function of the electrical contact will be explained according to the first exemplary embodiment (Fig. 1). It is assumed that the contact is formed by two identical contacts according to FIG. 1, so that in the switched-on state both contacts are contacted at the base of the arc 41. Upon opening, an arc 41 is formed which gradually moves to position 42 under the magnetic field. In doing so, its heel burns from the surface of the quench liner 21. Since the ionization stress of the quench liner 21 material is higher than the ionisation tension of the contact body material 11, the arc must correspondingly arc the voltage with which it burns. increase. The increased arc voltage contributes to the instability of the arc and without looking3

238 99!

for other means used to extinguish the arc (the shape of the arc chamber and the current path, the use of a magnetic field or the flow of air or other extinguishing medium etc.) contact actively contributes to arc extinguishing, reducing its burning time and thereby increasing the service life. but also the device in which the contact is built-in ·

Claims (1)

SUBJECT OF THE INVENTION 238 999 Electrical contact for contact switching devices, comprising a body of contacts and a flame-retardant liner, characterized in that the material of the flame-retardant liner is at least partially selected from the group of oxides, sulfides, carbides, nitrides, borides or phosphides of metals and its ionization voltage is higher than the ionization stress of the Jcontact body.