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Line Frequency or rotational Speed?

Line Frequency or rotational Speed?

Line Frequency or rotational Speed?

(OP)
Hello,
making vibration on 2 pole generator (3000RPM) often the 1X can be confused with line frequency.
Keeping apart both are linked togheter, sometimes there are necessity to understand if 50 Hz vibrations coming from mechanical 3000 RPM of generator or phase unbalance (or any other electrical source problem).

What type of test you suggest in order to identify the source of the problem? it is mechanical or electric?

Regards

RE: Line Frequency or rotational Speed?

You could:
Measure vibration spectrum (FFT) with high resolution for accurate vibration frequency. It should be less that 50-Hz for induction motor with load.

Measure vibrations and shut power off. Mechanical vibrations will remain momentarily until speed drops.

Usually electrically induced vibrations are at 2x line frequency, and 1x line frequency vibration is rare.

Walt

RE: Line Frequency or rotational Speed?

(OP)
THank you strong but i think all you suggested is useful for a asynchronous motor and not for 40MW generator

Effectively:

-Measure vibration spectrum (FFT) with high resolution for accurate vibration frequency. It should be less that 50-Hz for induction motor with load.

Generator have to be connected with line frequency so have to be exactly as the power line frequency

-Measure vibrations and shut power off. Mechanical vibrations will remain momentarily until speed drops.

This should be usefull but it is not so simple disconnect Generator from line and restart again more complicated than a normal asynchronous motor

Anyway thank you for your support

RE: Line Frequency or rotational Speed?

You did not say synchronous generator or 40-MW size in your OP.
You could run to full speed no-load for mechanical vibrations
Excitation on for electrical fault (I did find a rotor fault this way)
Load versus to time for thermal issues

Yes, these are more complicated than for asynchronous motor, so you need a good reason for doing the tests!

Walt

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