MV motor dropped

[antonino]

hello
a MV 450hp 4.16kv motor was dropped at the client,
site. Both endshields were broken, sleeve bearings too.
Rotor and shaft look good.

Do you think that the motor shop could just replace the damaged parts, makes tests and the motor will run fine.?

I apologize if this is a trivial question, but I am just asking for opinions

rgds

 

[davidbeach]

I'm not a motor expert, but if it was dropped that hard there are all sorts of things that might have happened that wouldn't show up in a visual inspection.

Did the coils shift in the slots?
was there any change in the lamination stacking of either the rotor or the stator?
Was there any deflection of the shaft?

Hopefully someone has good insurance.

 

[DaveScott]

Shaft could be slightly bent: check balance, air gap.

 

[Skogsgurra]

Test run it at low speed (an LV VFD can be used for this) and see if there are any mechanical problems like run-out, balancing problems etcetera. Also, do a hipot test and perhaps a ring test to see if the stator iron got damaged. Check bearings for indentations (often detected if you do an SPM measurement).

Gunnar Englund

http://www.gke.org

 

[MikeHalloran]

Someone should be talking to the insurance carrier about this incident. Broken bearings bode ill.



Mike Halloran
Pembroke Pines, FL, USA

 

[electricpete]

Some other things to think about in terms of inspections/tests to make yourself comfortable before you finally accept the motor.

Inspect stator for broken welds between core and frame.

Visual inspection of rotor.

Inspect end-turns for any signs of cracking (not likely).

Do core loss test for signs of core damage (not likely).

Check shaft T.I.R. Check airgap both static and dynamic after assembled.

Specify electrical tests. (megger, surge, hi-pot).

No-load run and check for normal vibrations, temperatures and currents.

Even with all the above tests, I'd still rather have a new one but you do what you can do.

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[ScottyUK]

Check core laminations for signs of smearing due to mechanical impact. If inter-lamination insulation is breached, core losses will rise in that area leading to localised hotspots. A motor of that size is probably a little small for an El-CID test or even a core loss test, but if sufficient factory data is available both might reveal useful information. Both are techniques which are normally used on much bigger machines, but the principles are applicable to smaller machines too.

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[macmil]

You do not specify if this is / was a new motor. If it was, the client should ask for a new, undropped, motor. It may be possible to repair the motor to as new but it isn't new. If I was the client i would push hard for a new motor, or else guiarantees that would make a new motor seem inexpensive. And yes if an insurance company is involved, get them into the picture.