Effects of system parameters and circuit breaker characteristics on switching large synchronous motors

Interturn insulation breakdown in stator windings resulted in the failure of thirteen 21000 HP synchronous motors. To confirm if the failures were caused by steep-front voltage surges, field measurements were conducted during switching operation of one of the compressed air magnetic circuit breakers in one of the affected plants. The results indicate that the number of motors running in parallel with the one being switched affects the magnitude of the generated overvoltage. It is concluded that the failures occurred as a result of breaker tripping during aborted motor starts (while running-up to speed).<
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