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When the soft starter switches to the bypass contactor after starting, the circuit breaker trips instantaneously, and the contacts of the contactor start arcing and stick. Ah, what is the reason?
This is a question that a customer asked me recently. He checked this question for a long time. He checked all the lines and soft starters in the cabinet, but found no problem. But as soon as the soft starter is started and switched to bypass, then there is a trip.
It can be judged from the fault phenomenon that there is a phase-to-phase short circuit in this line. Since it has checked all the control parts, it means that there is no problem with the control part. As I can see from this wiring diagram, the phase sequence of the contactor and the soft starter are inconsistent. When the customer was debugging, he found that when the soft starter started, the motor reversed, and he dropped the two wire pairs at the lower end of the contactor. That's the crux of the issue.
We know that at the moment when the soft starter is switched, its contacts have not been completely separated, and once the bypass is connected, if your phase sequence is inconsistent, it must be a sudden short circuit. Therefore, everyone must pay attention after wiring the soft starter. As for the phase sequence of the input and output, your wiring must correspond one-to-one. For specific wiring, please refer to the instruction manual.