Defected 200kw Motor rotor

[Emad Shaaban]

Is there any method to detect failure in the rotor of a 200 kW motor that produces a humming noise? In a previous experience, a similar motor exhibited a similar noise, and upon disassembly, we found that its rotor had elimination gaps.

I am wondering which technique could help determine whether the motor has the same issue without taking it to the workshop. Please note that the motor is controlled by a Sepam M20, and all bearing readings are sufficient.and what is the reasons behide this issue ?
please see Pictures

 

[panter]

There is probably a problem with breaking some rod on the rotor. This can be detected reliably when motor is running under load using the Motor Current Signature Analysis method or vibrodiagnostics .

 

[Emad Shaaban]

thank you Panter.
Is there any space to tell me more about these methods

 

[waross]

You may try energizing one winding with DC and then turning the rotor.
You may be able to detect a cogging or a variation in the torque required to turn the rotor by hand.
And then, maybe not.
It depends.
It is a quick and easy test, but not always conclusive.

 

[panter]

thank you Panter.
Is there any space to tell me more about these methods

I used this technique 20 years ago with old SKF CMVA 60 instrument. Today there are many others that offer current analysis in one or all three phases of AC motor , so you have to do a little research. I am attaching a document of SKF on how it work and how vibration diagnostics can together provide signals and a reliable assessment that something is wrong with rotor cage.