Interruption tests on high-voltage air-break contactor

HIGH-VOLTAGE air-break contactors are frequently used in controllers, both for starting motors and for interrupting short circuits. According to the National Electrical Manufacturers Association (NEMA) standards,1 2,300- to 4,600-volt contactors for this duty may be used in circuit locations where the available symmetrical short-circuit kilovolt-amperes (kva) are as high as 50,000 kva. In this paper new contactors designed for this service are described, and the tests made to prove the interrupting rating are discussed.