Hi guys,

Please have a look at this rotor spectrum data taken with a pdma unit. The sidebands have increased to 36 dB it was at an avg of around 38-40 dB since Jan 08. Motor is tested monthly. There is no audible noise when standing next to the motor. I suspect Rotor bar problems, what do you think. Also activity at the 5th harmonic. Offline testing is going to be performed asap.
Motor specs(NP) = 6,6 kV AC Induction motor, 300 FLA, 2900 kW, 1490 rpm.
Stroboscope rpm was taken 1491,1 when running at 249.59 avg. amps

Thanx

This appears to be a 4 pole motor operating on 50 Hz AC. Please confirm. Can you provide the sideband spacings. These appear to be more than poles X slip.