Tungsten Copper Arcing Contacts for SF6 Circuit Breakers

Introduction

Tungsten copper materials are used for arcing contacts in SF6 circuit breakers for high and medium voltage applications. At the heart of the switching chamber, tungsten copper arcing contacts are exposed to extreme mechanical and thermal stresses. During arcing, the temperature can reach levels ≥ 20,000 K, for instance.

Tungsten copper has unique material properties. A high level of temperature resistance is one of the most important advantages of tungsten, while the copper content increases the electrical and thermal conductivity.

Advantages

Excellent arc resistance

Outstanding electrical conductivity

High strength

Good machinability

Very good thermal conductivity

Low thermal expansion

General Content

By choosing the right proportions of tungsten and copper, we are able to optimize the product's arc erosion properties. We obtain the lowest arc erosion rates at a tungsten content of 80 % by weight. Depending on the voltage and current intensity as well as on economic considerations, we can vary the tungsten content between 60 and 90 % by weight to meet your exact requirements.

Application

The arc erosion behavior of tungsten copper is also affected by the grain size of the tungsten, depending on whether it is used as the cathode (C) or anode (A) and in an SF6 or air atmosphere. The higher the applied voltage and current, the more resistant to arc erosion the contact material must be. We are able to modify the arc erosion resistance of WCu by, among other things, choosing the right grain size for the tungsten.