Factors governing the severity of prestriking transients in motor systems

Computer studies have been carried out to examine what factors determine the severity of switch-closing transients in a cable-connected motor system supplied from a complex source. The studies were based on a single-phase system representation simulating first-pole-to-close conditions. Busbar lengths and configurations were found to be of fundamental importance in defining transient severity. Short-busbar lengths and parallel-busbar configurations gave rise to particularly severe transients. The effect of increasing the number of cables connected to the busbar was found to be not as severe as expected, due to the presence of the short-busbar subsections in between the cables. Stray capacitance local to the motor-controlling switch, although not usually taken into consideration in such studies, was found to be a factor of some importance. Motor cable length and motor parameters were found to be of lesser importance