On the phase sequence identification issue of soft starters
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One of our facilities is powered by a low-voltage 380-volt power supply system. Once, after the soft starter was installed and tested, a few days later the phase sequence of the power supply changed due to maintenance work carried out in the upper-level power distribution room. After power was restored, motors that used other starting methods operated normally； However, the soft starter cannot start, and a fault signal is continuously generated (the fault code is incorrect phase sequence). I hope those with more experience can advise me on why this is happening .
Whether the phase sequence is correct – here, this refers to whether the phase sequence required by the soft starter matches the phase sequence of the power supply.
The solution is to simply pour the two phases in arbitrarily. The reason may be related to the phase shift of the thyristors connected in anti-parallel in the soft starter device. It is better to consult the manufacturer for the specific reasons.
The issue mentioned above relates to the phase sequence of the power supply; for conventional starting methods, the three phase sequences of ABC, BCA, and CAB can be considered equivalent, and the direction of rotation of the motor will not change. For soft starters, operation in the ABC phase sequence may be allowed only; all other phase sequences are considered incorrect ； The question is how it distinguishes between the above three situations.
Whether the phase sequence is correct – by phase sequence here, it is meant whether the phase sequence required by the soft starter matches that of the power supply; in other words, whether the phase sequence of the soft starter corresponds to the A, B, C phases of the power supply
Refer to the manual to find out the cause; it may be due to a change in the phase sequence of the control circuit. Generally, a change in phase sequence should not affect operation.
Generally, a change in phase sequence does not affect operation, but the motor will rotate in the opposite direction, which may not be acceptable in certain processes. Some medium and high voltage soft starters have requirements regarding phase order, but American Mototronic can automatically adapt to it.