Short-Circuit Testing of Combination Starters with Inverse-Time Characteristics to UL High Available Fault Standards

Short circuit tests at 18, 25, and 65000 A on combination motor starters with circuit breaker protection are discussed. The appropriate failure criteria from Underwriters´ Laboratories (UL) high available fault standards are referenced. The specialized test equipment required to do these tests are mentioned. Characteristics of the combination starters are described as they relate to short-circuit performance. Finally, the portion of short-circuit energy dissipated in the current arc, arc chutes, circuit elements, contacts, heating of the air, and pressure in the enclosure are measured or calculated where possible.