Erosion dependency of 3-phase contactor contacts on configuration of loads

Following the concept of symmetrical components and trigonometry, derived expressions for the voltage across nonarcing open contacts of three phase contactors used with various load configurations are discussed. The validity of the derived relations is examined experimentally. A phase current of 20 A at a line to line voltage of 415 V and a gap-length of 2 mm on Ag-SnO/sub 2/ contacts are used for 5000 operations with loads arranged in delta and star configurations. An inspection of SEM photographs demonstrates the dependency of erosion upon load configurations.