One Half of a Part Wound Compressor Motor is Burnt

Hello,
I read an article about "Reciprocating Compressor Failure Modes" in "www//fridgetech.com". I have some questions about this article and also i want to give some information about my problem...

In article followings was writen:

If there is "Burning of One Half of a Part Wound Compressor Motor" problem, check for the following causes:
1. Faulty control circuit.
2. No interlocks.
3. Blown contactor

Could you please give me detail informations about the folowings:

system information:
There is a cooling unit in one of our customers. It has three compressors and two circuit. One circuit has two compressor. First compressor of the circuit is always running, second compressor is running only when the capacity is not enough.

Problem:
This second compressor was burnt. We checked it and We saw that only one of the winding of compressor was burnt. (compressor has two winding)
And the rest of the compressors were working very well. If there is a problem on control circuit i think the other winding of second compressor was burnt. Could you please tell me how can i understand There is an interlock problem or contactor problem?
Can you give me some informations about "interlock problem", "contactor problem" or the other reasons you thought?

I am waiting for your comments urgently.
Best regards

marc is currently with a british manufacturer doing 'stuff'

carrier were big fans of partwind compressors..


the first stage should have an interlock on the contactor which will prevent it from pulling in unless the contactor is energised.

however there is usually no interlock on the power thus if the fuses have blown it will sense that the contactor has pulled in and will energise and run on one set of windings

fualty control circuit could include rapid cycling of the contactor, not energising at all ,too long a delay between stages

i feel that you should first find out which set of windings burnt out then report back..

not much -but it's a start ;-)

cheers

richard

Hi!
A part winding motor has two windings that must start separately with a certain interval or timed gap from each other.

This timed gap is either controlled by a timing device or simply they just start one after the other in sequence.

Timed gap with a timing device is achieve by interlocking a timer to energize the second contactor on a preset delay after the first one. Common preset delays are 1sec to 6sec.

Sequence start is achieve by energizing the contactors one after the other in interlocking sequence. This does not requires a timer

Common probs of partwindings are:
1. faulty timer- The timer fails to start the second contactor. If the overload relay on the first winding is not set properly, then it cannot stop a burnout.
2. wrong phasing - one turns to the left and the other to the right, the weak will give up first.
3. Spot Burn is not related to controls. It may be cause by some abrasive materials that come in contact to the winding and scratches its insulation. If it is a refrigerant cooled compressor, then the abrasive materials may comes from the mechanical parts that wears off.

I hope these help.