How do you measure the air gap?
How do you measure the air gap?
(OP)
We have a GE 32000 Hp synchronous motor and we would like to measure the rotor stator airgap. Is it best to use long feeler gauges or just do point measurements around the rotor?





RE: How do you measure the air gap?
Is it salient pole or smooth rotor?
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RE: How do you measure the air gap?
RE: How do you measure the air gap?
Respectfully.
RE: How do you measure the air gap?
Also, for salient poles, you have to make sure that you are measuring the air-gap at the center of the pole, where it is minimum. No need to turn the rotor unless you're measuring the rotor or stator run-out.
Muthu
www.edison.co.in
RE: How do you measure the air gap?
There is at least one that does. API 1068;
[QUOTE API 1068]Centering of the rotor within the stator should be checked, whenever permitted by the machine
construction, by both stationary gap and rotating gap feeler gage readings at both ends of the motor. Readings should be taken at not less than three points 90° apart around the rotor periphery. In the stationary check, feeler gages are inserted successively at the separate points and the values are recorded. In the rotating check, the gages are left at one location and the rotor is turned in 90°
steps, noting the reading at each step. This test can reveal an eccentric rotor that may go undetected
by the stationary test. Readings shall not exceed a 10% deviation from the average at each end.
(See API 541-1995, Section 2.4.7.16.)[QUOTE]
What I described imo accomplishes the intent of both tests.
From their discussion you see as we all know there is stationary eccentricity (basically lack of centering) or rotating eccentricity 9typically runout).
If rotor iron runout is small for example < 0.002", then probably the stationary test is good enough.
If rotor iron runout is 0.005" (as is common for our very large motors), then you see the rotor TIR is on the same order as the 10% airgap acceptance criteria... tough to ignore it imo.
At any rate, it was a good clarification. Certainly rotating rotor is not required for smaller motors and many standards. Some standards and customers (like me) prefer it for reasons discussed above
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RE: How do you measure the air gap?
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Eng-tips forums: The best place on the web for engineering discussions.
RE: How do you measure the air gap?
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