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Hi, profesional 

Do you have any experienced or standart "how to detect rotor damage" during running measurement inspection? Recently our old plant got burnt motor twice in rotor damage, how do you inspect before it happen so we can prevent damage?

based from our view, vibration analysis (FFT/Time series from velocity/acceleration and viewble temperature spot cant tell us the symptoms.




Original Post

Thanks mr kumar for reply, 

there are different motor, but same damage, i still refigure out how "source" problem and can affect the damage of rotor. 

For now we just use vibration analysis using accelerator sensor portable only, didnt have MCSA so cant be look far.

Our motor are 40 years old aging, and its didnt have any manufacturer guidelines, that the problem, because its customize motor as far i know from build factory. Maybe you have some guideline for typical motor, ? 




This site has a motor testing segment, see above link, you can search for "rotor bar testing" or "motor current signature analysis" or MCSA or MCE or PDMA, all should return a list of responses

Yes, vibration can see rotor bar problems, yes, motor current signature analysis online can see a bad rotor bar. Not knowing about access to your rotor, have used a strobe light, mirror, camera to record video and slow motion video while running to see cracked/bad rotor bar.

There are a lot of details missing from your "problem motors" story to aide you much further " we got burnt motor twice in rotor damage"?? Details....

Common things one would see/hear with bad rotor bars, loud beat frequency, motor runs hot, motor draws high amps, analog meter monitoring current will show continuous swing in motor amps but yet load is stable, 1x rpm will increase or machine will vibrate motor, pole pass frequency sidebands around 1,2,3,4,5x rpm, this is a short list, there are more tests than what is listed

I question why are the rotor/s failing?

Not all motor are built the same, there are 4 different "designs" of electric motors, the different designs have different torque curves for different applications, not ALL motors are built the same. Just based on what you have posted, I have to assume you have a large load to get started? This alone puts large stresses on rotor, mainly during startup. If the motor starts many times a day, this too will shorten rotor life

Yes, there are several technologies capable of identifying bad rotor bars, whether online tests or offline tests


Rotor damage can be detected through vibration analysis as it will reflect in a increase in rotor bar frequency.

Rotor bar frequency= no of rotor bar * running speed

Along with this I also try to inspect the presence of line frequency ( Supply electrical frequency) by limiting the Fmax to 10K & higher spectral resolution.

However the motor internal defects can be determined easily & much earlier in MCSA

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