Tungsten Copper Vacuum Contacts
Introduction
Tungsten copper contacts are used in the vacuum arc-quenching chambers (VACs) of highly dependable, quick-acting vacuum circuit breakers capable of breaking large currents in high-voltage 6-35 kW electrical networks. Tungsten copper vacuum contact is a key element in commutation switches (circuit breakers). Currently, the most common material used in contact pairs in VACs are W-(50-90%)Cu composites.
Tungsten copper vacuum contacts are subjected to the effects of short-circuits currents and fusing metals in various points of the surface due to the high density of the current in them; as a result, welding joints form in these zones. This problem was one reason that delayed the development of vacuum commutation technology for more than twenty years. The resistance of a VAC's contacts to welding is one of its key characteristics. The problem of welding was solved by developing special contact plates made from tungsten copper composites, which provided a high breaking capacity for circuit breakers in commutation networks, wear-resistance and resistance of contact pairs to welding.
Application
Tungsten copper contacts are used in VACs of vacuum contactors with a nominal voltage of 1.14 kW and higher in systems for remote control of electric drivers. Tungsten copper vacuum contacts are a long-lasting means of switching contactors in electric circuits on and off and ensure a low cut-off current in the system.
Characteristics
Two types of products are manufactured: disks made from a composite tungsten copper material and complex parts consisting of a contact tungsten copper layer and a copper substratum. High-quality POLEMA-produced electrolytic refined ERC99.95 chromium is used in making these parts. Tungsten copper vacuum contact material is distinguished by high purity in terms of gas-forming and metallic impurity content, outstanding phsyical and mechanical characteristics.
Contract parts consist of two heterogeneous layers (bimetallic structure): a contact layer made from a tungsten copper material and a substratum made from copper.