Closed-Loop Solution of Transient Recovery Voltage for Interrupted Induction Motor Starting

When the starting of a large (>1000 HP) induction motor is aborted and a circuit breaker interrupts the current, a transient overvoltage is observed. The magnitude of this transient is greatest for the first interrupted phase; hence the behavior of only this phase is studied. The motor at standstill is modeled as a three-phase reactor with an isolated neutral. Analysis of the transient phenomenon is intended to extend and complement Greenwood´s and Glinkowski´s work which are based on empirical and circuit analyses. The object is to arrive at an exact closed-loop expression that completely describes the transient recovery voltage resulting from such a transient event. An example of the application of this expression is supplied, and a simplified expression that may be used for quick calculations is also provided. Two quantities of importance, the rate of rise of recovery voltage and the peak voltage of the transient, are obtained, and a method to limit them is discussed.