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Member Since 29 Oct 2010
Offline Last Active Oct 31 2010 02:03 PM

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Motor Start Problem

31 October 2010 - 02:03 PM

We are having a really interesting problem!

We are commissioning two brand new 4160V Siemens motors 900HP and 1600HP. The plant has a 15kV/4160V transformer for just these two motors. The motors are soft started.

The motors are ramping up but then trip right away on voltage imbalance and ground fault. The interesting thing is that both motors are tripping on the same fault, voltage imbalance on the exact same phase. B is about 30% higher than A and C.

We just had the transformer tested, which is brand new too, and the transformer is OK! We also bypassed the starter by ramping up in 2s and we are getting the same fault.

Does anybody have an idea what the solution to this problem could be?