Motor winding dry out?

paramasivan4u; you could use low voltage direct current to warm the winding.perry

i want details about all my question,can u explain me details

paramasivan4u: usually motors are dipped & baked in varnish or an epoxy when they are manufactured, you could use a controlled oven to bake them again. were all the winding in the stator burnt or dis colored? the motor may have single phased which would burn out one winding, rather then all windings, perry

all phase winding are burnt

paramasivan4u; do you use motor overload protection? it sounds like it is undersized for the load, or the load was dragging the motor down, may be mis wired or wrong voltage. how long did the motor run before it smoked, was it under operating conditions? perry

I have previously posted this in another forum.

http://www.eng-tips.com/faqs.cfm?fid=1157

Hello..

How and what ...for.. Motor winding cleaning and dry out, has been discussed in this forum, please read the topic title as below, posted dtd Dec 24, 2008

Motor externally by spraying water?

Good luck

Rgds

Sis

Dear PAramasivan,

By your statement, It is saying that, motor burnt, because of moisture aberve while storage, But there are so many reasons behind motor burning after replacement of existing burnt motor. naturally you may have checked ohmic valve, megger value and free roatation of motor before installation.

there may be different reason behind this, may be over loading / wrong wiring / wrong voltage , this are the reason burnt all three windings. moisure observing may damge insulation failure not complete winding burning.

for better understanding, send photo's of defective motor.

bye

Keshavamurthy

To decide if a motor has absorbed moisture conduct a polarisation index test. Look up how to do this either in earlier threads I've subscribed to or google the topic. Moisture shows very plainly by this test. If you decide there is moisture to remove a DC welder adjusted to provide no more than full load current will warm it up gradually. Considering that DC will not excite all 3 windings equally swap connections as necessary.

Of course an oven is better but not always available.

As already stated, low voltage DC is a common option. I've seen people carefully use welding machines for this purpose.

Large motors and generators in most cases easily accept heaters (heat strips) that are simply plugged into a wall socket.

Please see recommended action before you replace yoour burnt motor:

1. if all phsaes of winding is burnt - you may have a lock rotor or your load side may have been stuck up, safety control enterlock suck us motor overload, timer had malfunction (XL, partwinding etc.)

2. as mentioned that unit, was put in long storage - possible cause is winding had been moistiorized, grease degreaded/moisturize and stuck up bearings.

3. to avoid such scenarios, please see list below prior to unit start up:

a. dry run controls

b. megged motor windings and resistance test

c. apply heat to motor winding (1000amps flood light at motor body) and monitor megger value for any improvments - you should achieve increasing megaohm value above 1000Mohs or infinity - if moto megger below <4Mohms

d. check motor sensors resistnace and connect to control enterlocks

e. if unit is installed with internal heaters, follow motor epcs concerning installation

f. run motor with out or with load and observed motor RLA

g. if motor megger is in doubts, monitor motor resistance say every 1hour or higher)

if above instruction will be followed accordingly, then i'm pretty sure that you will run the motor at normal operation .

Feel free to email: nlparedes2006@yahoo.com for more info if required.

nelson1; i sure you meant 1000 watts, not amps in answer "c" . perry

I was involved for twenty years in the manufacturing of electric motors for ABB in Australia.

The motors are dipped & baked in an epoxy varnish and baked until the epoxy goes hard.

We use to store motors in an open warehouse some time for more than two years.

No drying precaution was taken before shipping motors out.

All our motors were manufactured to be installed outdoor.

The baking was done by passing DC current through the windings.

I would suggest that the problem was not caused by moisture during storage.

To dry a motor out, you could pass DC current through the windings or in an oven.

The temperature will depend on the insulation class "F" or "H".

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