Contact material and arc current effect on post-current zero contact surface temperature

Optical radiation measurements of contact surfaces were made after current-zero of a high-current (>10kA_p) arc, to determine how much the contact surface temperature at and after current zero was affected by a change in contact material and arc current. Contact surface temperature was measured for different types of "typical" contact materials (AgW and AgC) commonly used in molded case circuit breakers (MCCBs). The average temperature at the contact surface was measured by using photodiodes in conjunction with a narrow band filters and long-range microscope. A 250-A rated MCCB was modified, with renewable chamber walls and contacts, and used as a test bed to insure that these results can be directly applied to MCCBs in the 125 to 250-A range. Uniform and repeatable arcing conditions were maintained by using an electronically timed capacitor bank source, timed contact part, and a well-maintained arc chamber. Along with other important engineering properties of the contacts (arc erosion, temperature rise), this data can be useful for selecting contacts for circuit breaker applications