Polarization testing of MV drives

[Ithaca]

Gents,

I have a 3 phase 60hz 11kV syncronous induction motor, 15 years old in the North Sea.

Insulation class B
Hazardous rated Exd

I intend to do a PI test PI= R10/R1, have you any information on what DC voltage I should use for this test.

The rule of thumb appears to be 2.5kV and I note IEEE 43-2000 refers to 1kV DC for machines post 1974.

Any help/advice appreciated on what the voltage should be?

 

[GTstartup]

I believe that would be 5kV per IEEE 43-2000

 

[glendale]

I would allways recommend using a 5kV megger, and you should be looking for a PI ratio of better than 2:1 ie the 10 minute reading should be better than twice the one minute reading.