MEDIUM VOLTAGE VACUUM INTERRUPTER CONTACT WITH IMPROVED ARC BREAKING PERFORMANCE AND ASSOCIATED VACUUM INTERRUPTER

Abstract

Electrical switching contact with radial magnetic field for a medium-voltage vacuum interrupter including a rod and a contact body, coaxial to the rod, which includes a disc and a circular element concentric with the disc and arranged protruding on a face of the disc, the other face of the disc being secured to the rod. The contact body has a spiral configuration; the disc includes slits in the thickness of the disc which extends from the periphery of the disc towards the centre of the disc; the circular element has an outer diameter smaller than the diameter of the disc. The disc and the circular element are made of a copper alloy with a refractory metal chosen from among chromium, tungsten and molybdenum, the alloy of the circular element including a proportion by weight of the refractory metal greater than that of the alloy of the disc.

Claims

1. An electrical switching contact with radial magnetic field for a medium-voltage vacuum interrupter extending on a longitudinal axis, the electrical switching contact comprising: a mechanical connection and current input rod which extends on the longitudinal axis; and a contact body which is coaxial to the rod and which comprises a disc and a circular element, concentric with the disc and arranged protruding on a face of the disc, the other face of the disc being secured to the rod; wherein the circular element is a ring and wherein the contact body has a spiral configuration, the disc comprising slits formed in the thickness of the disc and which extend from the periphery of the disc towards the centre of the disc, and the circular element having an outer diameter smaller than the diameter of the disc, and wherein the disc and the circular element are made of a copper alloy with a refractory metal chosen from among chromium, tungsten and molybdenum, the alloy of the circular element comprising a proportion by weight of the refractory metal greater than that of the alloy of the disc.

2. The electrical switching contact according to claim 1, wherein the disc and the circular element are made of a copper alloy and of chromium, the alloy of the circular element comprising a proportion by weight of chromium greater than that of the alloy of the disc, the proportions by weight of copper in the alloy of the disc being between 50 and 95%, the balance being made up with the chromium, and the proportions by weight of copper in the alloy of the circular element being between 40 and 80%, the balance being made up with the chromium.

3. The electrical switching contact according to claim 2, wherein the alloy of the circular element comprises at least 50% by weight of copper.

4. The electrical switching contact according to claim 3, wherein the alloy of the disc comprises 75% by weight of copper and 25% by weight of chromium, and the alloy of the circular element comprises between 50 and 60% by weight of copper, the balance being made up with chromium.

5. A medium-voltage vacuum interrupter comprising at least one electrical switching contact according to claim 1.

6. A medium-voltage vacuum interrupter, comprising a pair of electrical switching contacts with a moving contact and a fixed contact, wherein each of the moving contact and the fixed contact comprises the electrical switching contact according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be better understood on reading the following description, given in a purely indicative and nonlimiting manner, with reference to the attached drawings in which:

[0021] FIG. 1, already described, is a partial vertical cross-sectional view of a medium-voltage vacuum interrupter;

[0022] FIG. 2 is a perspective view of a pair of switching contacts according to a first embodiment of the invention;

[0023] FIG. 3 is a perspective view of a pair of switching contacts according to a second embodiment of the invention.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0024] According to the invention, the electrical switching contact is a contact with radial magnetic field and, more specifically, of the spiral type. Examples of this particular spiral configuration are represented in FIGS. 2 and 3. As is known, this spiral configuration is characterized by a contact body comprising a disc provided with slits and a circular element, protruding on a face of the disc having an outer diameter smaller than that of the disc. In FIGS. 2 and 3, four identical slits 11 are formed in spiral-fashion in the disc distributed at 90° from one another along the circumference of the disc and starting from an inner diameter (which can be less than, identical to or greater than the outer diameter of the circular element), to the periphery of the disc. It is perfectly possible to have a different number of slits, for example three slits distributed at 120° from one another along the circumference of the disc. The slits can be curved (as represented in FIGS. 2 and 3) or else rectilinear.

[0025] Referring to FIGS. 2 and 3 representing a pair of electrical switching contacts according to the invention, each contact 2, 3 comprises a rod 4, 5 at the end of which is arranged a contact body 6, 7, which is coaxial with the rod 4, 5. Each contact body 6, 7 has a spiral configuration and is provided with a disc 8, 9, one face of which is secured to a rod 4, 5, and with a circular element 10 (only a circular element is visible), arranged protruding on the other of the faces of the disc 8, 9.

[0026] As is known from F. Hauner et al., “CuCr for Vacuum Interrupters—Production, Properties and Application”, International Conference on Electrical Contacts, 2008, an electrical switching contact can be produced by different techniques: by sintering, by vacuum arc remelting (VAR method), by vacuum casting, by vacuum-induced melting, by vacuum infusion (the vacuum infusing process or VIP method).

[0027] The different parts of the contact are produced separately (rod, disc and circular element) and then assembled.

[0028] In the context of the present invention, we have for example produced a vacuum interrupter with two contacts each having a disc made of Cu.sub.75Cr.sub.25 alloy (% by weight) and a circular element (of pellet or ring type) made of Cu.sub.50Cr.sub.50 alloy (% by weight) and obtained by VAR. In another example, the circular element (of pellet or ring type) is made of Cu.sub.60Cr.sub.40 alloy (% by weight) and is obtained by sintering.