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What are root causes for higher starting current in HT motor (500 kW, 3.3 kV)

I have replaced all stator coils of the 500 kW 3.3 kV motor. The winding phase resistances are exactely equal to the designed one, also the insulation is tested (HV Test & Tan Delta- Capacitance test) and is OK. But during No Load trial of the motor, the no load current has exceeds the limits and hence, the breaker got tripped off. Other motor works satisfactorily with the same breaker. Let me know about the reasons/ root causes for such high starting current in HT motor, Please.

Reply to
sunilkeluskar
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The winding is not the same as the original. It sounds like some coils are connected backwards or otherwise out of the proper sequence.

Reply to
Fred Lotte

Thus spake snipped-for-privacy@gmail.com:

Sunil, I know nothing about 3.3 kV equipment, but if my math is right, that motor should draw about 150 A.

What size is the breaker?

Is this a 3 phase motor?

Are windings connected correctly?

What does the manufacturer's support rep have to say? (If replacement windings are available, I presume support is also available...)

Sparky

Reply to
SparkyGuy

The resistance of the windings is of very little importance!!! The most important issue is the number of turns in each coil!! because it is the number of turns that create most of the "impedance", which determines the current the motor draw with or without load!!!

Reply to
AL BENSER

As the others have mentioned, it is the number of turns and proper connections that come to mind (especially since it was just rewound??).

Another item is check the air gap for the rotor. If the rotor is off-set in the stator iron (unlikely, but possible), then the wider air gap can cause higher current surge.

But my money's on the coils are not connected correctly. (worked in a rewind shop for a few years, seen it before, it happens).

daestrom

Reply to
daestrom

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