We have the customer use MCEMax to measure and diagnosis the condition of wound rotor and they have a good condition for this wound rotor with RTG =5000Mohm and PI = 5.1 with smooth graphic, but after three months later when this motor running in normal condition the customer turn off this motor after that they start again and 2 minutes later the Rotor was burned and this rotor was destroyed ( You can see this in attached file). Could you give me some ideas for this problem to explain for customer? If have short turn in windings of this rotor so How long from they have signals to complete destroyed with your experience? Thanks

P/S: this ABB motor 6.6kV, 350kW

Huynh,
If you can send the file to my email address (cyung@easa.com), I can probably shed some light on this failure. With wound rotor machines, we occasionally see a failure in the rotor caused by the transformer effect between rotor and stator -- very similar to a Reclosure or rapid restrike: If the stator is energized while coasting down, before the magnetic field has fully diminished, restarting the motor can damage the rotor.
It would also be helpful to know the poles, as there are some specific combinations of circuits & poles that can contribute to the problem.
Chuck

Dear Charles.m
Please check email. I have already sent the picture for you. Please help me.

Hello Huynh (Charles, Members).

I also can't see the file you refer to in the post. Could you email it to me as well please? melaia@mweb.co.za
Thanks.
Robert.