I've seen 2 similar cases:
a) harmonic distortion (pulp and paper).
Back of the envelope calculation on the nameplate suggest that the pf at full load should be about 0.5.
Overloading should cause the pf of the motor to rise above nameplate, and not drop below it. Lower pf can be caused by...
To RalphChristie,
I agree with your quotes; but [COLOR=red]CAUTION[/color red] with the a) alternative (manual push), because:
1) until it is being pushed on, the motor sees short circuit currents of 6-10 times rated current levels in the energized windings (it will burn about as fast as a...
I agree with electricpete. The best way is to look for the sidebands around 60Hz in the current spectrum.
WARNING! There is a chance to identify something as rotor bar problems, yet it really was an oscillation of the load. The rotor bar signature is on one very definite spot (as a function...