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Issue on Motor Vibration
2

Issue on Motor Vibration

Issue on Motor Vibration

(OP)
We're running the motor (300kW) and people have tried to get rid of vibration on it.

I've though that vibration is only about mechanical part and nothing to do with electric.

Somebody asked me if there is any elements in terms of electric that need to be considered.

Do you think there is any part we need to care as an electrical people?

please give me any advice.

RE: Issue on Motor Vibration

Often the electrical part creates torque pulsation that drives vibration and resonant responses, so yes, electrical can be involved.

Motors with open windings or partial failure issues can cause lots of vibration.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Issue on Motor Vibration

You need to care about all the parts.

The forces within the motor that originate from current flow are much larger than the forces with a strictly mechanical origin in any motor that hasn't suffered severe mechanical damage in some way.

If possible spin the motor with some external mechanical power source, with no electricity applied to the motor itself. If that reveals no serious vibration, then...

Start by looking for unbalances among currents that should be symmetrical.

... and that's pretty much the limit of my expertise in electric motors, but maybe one of our real experts will chime in soon.



Mike Halloran
Pembroke Pines, FL, USA

RE: Issue on Motor Vibration

Yes, there are electrical malfunctions that can produce vibration in a motor. In order to help you, we need more specific information about the motor and the vibration.

What speed is it running at?
Is the motor uncoupled or driving something?
Rolling element bearings?
Has the vibration been measured? Amplitudes? Frequency content?

Answering these questions would be a start to your investigation.

RE: Issue on Motor Vibration

Nice tip Mike Halloran.

Chuck

RE: Issue on Motor Vibration

There is a lot of information about motor electrical and mechanical vibration sources. A simple search will reveal a lot.
Google: motor electrical vibrations
The dominant vibration frequency from electrical dynamic force is 2x line frequency (either 100-Hertz or 120-Hertz) that is caused by magnetostriction. Some other important electrical frequencies are pole pass, rotor bar and stator slot pass frequencies.
"I've though that vibration is only about mechanical part and nothing to do with electric." Vibrations are the result of dynamic forces acting on the structure. Tip of the iceberg here!

Walt

RE: Issue on Motor Vibration

Vibrations are often caused by uneven air-gap.
In case of 300 kW motor always is desirable to apply a winding connection which will reduce vibrations caused by uneven air gap.

Motor Repair and Winding Design

RE: Issue on Motor Vibration

I haven't figured out what kind of motor it is. VSD or Constant Speed, DC, ASIM, PM, WRIM etc?

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Issue on Motor Vibration

You haven't told us what the motor is driving.
In many cases electrical vibration will cease the instant that the motor is disconnected.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Issue on Motor Vibration

There are a lot of good references on this topic, like this one the electrical influences on motor vibration,
http://www.bksv.com/doc/BO0269.pdf

This Siemens paper is an excellent resource, http://www.industry.usa.siemens.com/drives/us/en/e...

When I approach a vibration issue with an electric motor driven system,

I start with a discussion on the history of the problem, is it a new install? Did it start after a repair? Did it start out fine and slowly get worse or did it increase suddenly.

What is the motor driving? Is the driven equipment/process changed?

A walk around visual inspection, how is it mounted, coupled, shimmed? Are there signs of mechanical damage, like cracks in the sheet metal, guards or support brackets.

I usually do a vibration analysis and collect electrical data with a three phase power analyzer at the same time if possible. Collect and review the data, see where the dominant frequencies are, see if the electrical data shows any possible contribution factors, and then work forward with the information collected so far to determine root cause from there. A possible corrective action may be apparent at that point, or the need to do further testing.

Some problems are fairly easy to figure out, some require a large amount of effort to make proper corrective action, a lot of factors involved and not many "easy fixes", at least for the stuff I work on most of the time.

MikeL

RE: Issue on Motor Vibration

Other posters have answered OPs main question about the existence of "electrically" induced vibration.

Absolutely To make any significant progress the First step is detailed vibration analysis, also as pointed out by others.

Also as mentioned by others, MUCH more info (words and pictures) about the equipment is required by whomever is working to fix the problem, if there is a problem

RE: Issue on Motor Vibration

Hi yk052052,

any progress on the motor vibration?

RE: Issue on Motor Vibration

Are there any devices used in industry to isolate vibration caused by an electric motor?

RE: Issue on Motor Vibration

Broken rotor bar(s) are another possibility. Somewhere I have (had) an article I clipped showing a vibration spectrum analysis profile that could be used to indicate a broken rotor bar, because it was relatively consistent and repeating. I had that as a paper copy, which may have been recycled now, but I'll take a look. If I'm not mistaken though, this has come up in here before and Gunnar (skogsgura) had shown something similar.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

RE: Issue on Motor Vibration

Quote:

Broken rotor bar(s) are another possibility. Somewhere I have (had) an article I clipped showing a vibration spectrum analysis profile that could be used to indicate a broken rotor bar, because it was relatively consistent and repeating. I had that as a paper copy, which may have been recycled now, but I'll take a look. If I'm not mistaken though, this has come up in here before and Gunnar (skogsgura) had shown something similar.
http://www.pump-magazine.com/pump_magazine/pump_ar...
link on degraded rotor bar detection. Vibration signature and current signature are discussed... current is a more definitive indicator (and prefer to check near full load). We've had 3 large motors with damaged rotor bar joints and evaluating a fourth right now.

op has got plenty of general info to go on... the Siemens link by catserv is a good one.
still no specifics from op...





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