Phase failure is a fault condition that can cause damage to the three-phase motor. The Lovato motor protection circuit breakers, SM series, are sensitive to phase failure and therefore save the motor from damages caused by this condition. It is possible to have two situations: phase failure at motor starting and phase failure when the motor is running. In the first case the motor usually can’t start. Staying locked with only 2 phases, a very high current is reached so the thermal protection of the motor protection circuit breaker will trip in a very short time. In the second case the motor continues to operate, but the phases that remain powered will draw a current that will be around 2 times the motor rated current with consequent overheating and the risk of burning. Furthermore, the motor working with 2 phases only can generate mechanical vibrations and consequent mechanical damage on the machine. In these conditions, the motor protection circuit breakers trip in a few tens of seconds which is an adequate time to avoid damage.

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