Hello, I have my All Test Pro 31 since a few months, and made some tests on 600V motor without any problem. Last week I began verifying a 300HP 4000V 1200RPM motor and the results on the Condition Calculator were in the red. The thing that I did not understand, is the wave form that I got. It look more like a pulse waveform. I’ve tried to change the frequency of the test, same result. Any idea?

If it is repetitive, then the rotor is OK, you are just seeing the number of rotor bars. If it is square wave, long space, square wave, then it may indicate a bad rotor.

Set the AT31 to impedance mode at 200 Hz, rotate the shaft to the lowest value. Note the value and begin to turn the shaft slowly. The value should increase and decrease for the number of poles of the motor (ie: 3600 = 2 poles = 2 increase and decrease). If the peaks and valleys (values) are not consistent, then you have rotor bar issues.

Sincerely,
Howard

Oh, and what were the values that put it in the red? Also, did you attempt rotor compensation?

Howard

Hello MotorDoc,
We send the motor for inspection at G.E. so i can't check the rotor for now. I join my report made with Condition calculator 3.0

As I understand this screen on the Condition Calculator 3.0, the rotor was compensated during the test. If so, then there is an issue with the winding.

In the future, one of the steps that I like to take with the AT31, when there is a separation of I/F and Fi, is change the test frequency a few times. If the range of 5 and 3, as in this test, does not change, then it is probably a rotor-related issue. Otherwise, it is a winding issue.

Howard