Voltage Data Loggers

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I've been burning up compressor motors and suspect I might have a voltage problem, although it is OK every time I check it. Does anyone have any recommendations for single phase voltage/ amperage data loggers? I saw one by Extech for around $300. Thanks
 

G._S._Ohm

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Monitor the compressor case temperature also. It can serve as a crosscheck on your other readings.
It can't hurt and you might as well get as much data as you can before the next motor burns up.

You can check the compressor supply source resistance with a 10 A or 20 A resistive load and voltmeter. You know the wire length and gauge so you can figure how much conductor drop you should have. If there is an excess I'd look for a bad connection.
 
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hurk27

Senior Member
I've been burning up compressor motors and suspect I might have a voltage problem, although it is OK every time I check it. Does anyone have any recommendations for single phase voltage/ amperage data loggers? I saw one by Extech for around $300. Thanks

While a data logger is a must for serious trouble shooting, there are some things that can be checked that might save having to buy one right away.

Common problem I have found are:

If reciprocal type:
Bad contact causing single phasing with wrong selection of over load.
Loose connection same as above.
Pressure set above the rating of compressor, again overloads should be protecting against this.
Wrong voltage motor, I.E. a 230 volt motor being used on 208, For high torque applications like in reciprocal type compressors you must used the correct voltage motor, 200 volt motor for 208v.

Rotary compressors:
Same as above for single phasing, and pressure setting.
If VFD is used, look to see if dynamic breaking was turned on, could be back feeding to much, or motor is not inverter rated, or line filters or chokes not installed.

Most common for compressors that have been in service for a while is the single phasing issue, but if the correct over loads are installed then this should not be a problem.
The only other thing is to use a clamp on amp meter and watch the current as the compressor get close to cut off setting, and compare to the FLA on the motor, do this for a few cycles to see if it over shoots the FLA.

Also a bad pressure switch can cause a compressor to over shoot the rated pressure which will cause the motor to over load, but again proper overloads should open for this condition.

If any work was done recently like some one change the pulley size, then make sure the correct size pulley was used.

Also make sure the motor cooling fan is intact, but as you said, the motor was replaced so this shouldn't be an issue.
 
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