Motors with Space Heaters Disconnected

[pattimelt]

I have two 30 HP motors that require heaters (due to job specifications) Because of a communication breakdown, they were brought to the job for installation which didn't take place; the temp power crew forgot to rehook the heaters up How long can they go without heat without this becoming an issue? Nite temps will be in the high teens, low 20's and it will be Monday at the earliest before connection can take place

 

[dpc]

The concern is mostly moisture, not the temperature. The motor windings should be meggered and a polarization index done to determine how much moisture the windings have picked up. If they do not test high enough, there are various methods of drying them out.



David Castor

http://www.cvoes.com

 

[jraef]

You can add Motor Winding Heaters that use the motor's power wiring to heat it from the inside by applying controlled DC current to one set of windings, turning them into heaters. They may be less expensive than a retrofit at this point.

Motortronics MWH Series
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[7anoter4]

I agree with jraef. But you can use AC voltage also. In the following article the anti-condensation heating consists of an AC voltage applied via terminals [U1 and V1]. See:

http://pdf.directindustry.com/pdf/s...exd-e-frame-size-63-450/13859-103178-_27.html

p.27

 

[waross]

My suggestion would be to do a megger test and possibly a Polarization Index test on Monday before the heaters are hooked up. Then at least 24 hours later do a second megger test and possibly a PI test. Repeat the tests on Wednesday and decide whether the motors are dry enough to be energized.
You may be good to go on Monday or Tuesday. It may take several days or a week to dry the motors.
It depends on the ambient conditions at your job site. There is quite a thermal lag in the stator and rotor when the ambient temperature is rising. If the ambient temperature rises quickly on a morning when the relative humidity is high, the dew point may rise above the temperature of the interior of the motor. When that happens condensation forms in the motor. This may happen at any temperature and may be worse in Central America than in Many locations in Canada.
It depends. If the motors stayed dry, they may even be good to go on Monday.
If ambient conditions have been unfavorable the motors may be damp or wet internally and you may have to dry them out for several days.
Let us know how it goes. We thrive on feedback.

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

 

[electricpete]

As long as you've got a day or 2 between when the motor space heaters will be hooked up and when you need to fire up the motor, I'd go with Bill's recommendation. There won't likely be any long-lasting adverse effects of a few days outdoors that won't be cured by a few days on space heaters and check of IR/PI for good measure.

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