A layperson is seeking help with issues related to motor starting via frequency conversion and soft starters. Thank you for following
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Thank you for your attention. There is a 110KW motor that has always been started using an inverter (for 5 years now). However, as a backup unit, it is hardly ever used. During attempts to start it, overcurrent errors occurred and the system shut down (the frequency cannot exceed 30HZ). When the load was removed and the motor was tested alone, overcurrent issues still arose (the system did not shut down until a frequency of 35HZ was reached). Later, a normal frequency converter was used; the motor tested fine with a megohmmeter; upon disassembly, the windings and bearings were all in good condition. After connecting it to a soft starter, it operated normally; switching it back to an inverter also resulted in normal operation. What could be the problem? I’m an amateur, so I’m not sure if my description is clear enough. Thank you for any corrections!
Have the parameters been adjusted? Is the acceleration time too short?； How far is the inverter from the motor, and is the capacitance to ground high? Are there reactors?
Have the parameters been adjusted? Is the acceleration time too short?； How far is the inverter from the motor, and is the capacitance to ground high? Are there reactors?
The motor and inverter are 30 meters apart; the key point is that by replacing the motor with another one at the same location and using the same inverter, normal operation can be achieved. After starting this motor using a soft starter several times, it worked normally again when connected back to that inverter
It is estimated that, as a backup pump, not being used for an extended period can cause slight sticking, which leads to overload during startup. When starting the pump with a soft starter, the starter’s overcurrent protection or the high protection current allows the pump to start. Once the pump is running, the stuck parts relax, and it can then be started normally using variable frequency control.