Fridge compressor probs...

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I picked up a small fridge compressor with the idea of playing around using
it for a SMD vacuum parts pick up tool, but it behaves strangely.

On initial power up it runs fine, very quietly. It quickly/easily pulls down
to 20kpa (-80kPa).

However if I disconnect the power and reconnect there is a quiet hum but the
motor is stalled. If I disconnect again then wait a minute or two before
reconnecting it powers on fine and will run fine - I've let it run for 5
minutes continuously with no problems.

As part of the terminals to the motor there appears to be a thermal overload
switch, it gets warm but not hot (guess ~30 Celius)

Heres a link to the data sheet:


http://www.transtech-co.jp/electronics/en/Library/compressor7.pdf

I vaguely recall something about fridges having protection against rapid
cycling of the power for some reason - but that could be rubbish.


Any ideas?



PS: neat home SMD vac pickup video:

http://www.youtube.com/user/mikeselectricstuff#p/u/8/pdGSFc7VjBE




Re: Fridge compressor probs...
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When used in  a fridge as designed if the power is removed then
reapplied quickly, the pressure of the gas will cause the motor to
stall. By waiting for a period of time for the pressure to disperse into
the pipework, the compressor will restart. this usually takes a few minutes.

The thermal overload device on the input terminals will sense when the
motor is stalled and results in the compressor cycling on for a short
time (about 20-30 seconds), then goes off for about 3-5 minutes.
Eventually the compressor will overcome the gas pressure and restart
normally.

Re: Fridge compressor probs...

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Thanks for the reply Art. Yep, I found a PTC thermistor under a cover on the
compressor. Google led me to more infor on how it works.

Now to play with making my SMD pickup.....

Thanks.



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