A new test apparatus was introduced to evaluate the welding characteristics of contacts used in circuit breakers and contactors. This apparatus, which consisted of Silicon Controlled Rectifier units in a test circuit, was able to simulate the switching operations of actual no fuse breakers and contactors under short circuit or overload conditions. The effect of the contact force and current on the weld tendency of several silver - base contact materials was examined under different switching conditions. Differences in the welding characteristics of contact materials can be easily distinguished from these experiments. A few weld test results using actual switching devices are presented and compared with those of the above mentioned test apparatus.
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