EROSION MECHANISM OF W-Ag CONTACT MATERIAL IN THE AIR-BLAST CIRCUIT BREAKER UNDER THE SHORT-CIRCUIT CONDITIONS

摘要

The paper discusses the erosion phenomena that occur in the W-Ag contact material applied in a Compact type low voltage air-blast circuit breaker (rated a.c. parameters: 30A, 500V, 50Hz). The breaking capability was tested under the conditions that simulated the short-circuit action of the breaker. In the test cycle, a short-circuit current of 19kA peak (cosΦ=O.3) was interrupted. After 3 min, it was turned on and then interrupted again. After the short-circuit test, changes in the contact surface and the structure of the contact material were examined. Based on the discussion of the results obtained and on an analysis of the physico-chemical processes involved, the paper discusses, in metallurgical terms, the possible mechanism of erosion that occur in the W-Ag contact material under the short-circuit conditions.