Motor Overheat...HELP!

[inchoate]

Hi guys,

I'm troubleshooting an overheated single phase motor and I need some help here. The motor overheated and tripped at less than 1 hr. The capacitor is still in good condition, and the amp drawn by the motor is never higher than the rated current. I didn't see any fluctuation in voltage and current either. the motor just overheated and stopped.

Any advise as to how to figure out the problem?

 

[DASKAT]

Check the cooling channels to ensure proper airflow. Also check dirt and paint build up on the surface of the motor which can effect heat transfer. Since current is steady that generally disproves any mechanical binding but if possible disconnect the motor from the load and check the current again unloaded and also for any mechanical binding.
TTFN
THE KAT

 

[skiier]

Are we talking about and internal or external overload unit here?
An internal overload in a single phase motor is generally a thermal element of some type and these tend to degrade over time as the motor ages- particulary if the motor is run near or at full load. What enviroment is the motor in? A high ambient temperature can also cause this problem. A dirty motor doesn't help either. Check to see if you have proper air flow in the right direction. Some mechanical equipment, like recipricating compressors, have cooling fans on pulleys that aid in motor cooling.
If it is an external overload and all the voltage and curent readings r ok than check the setting of your overloads or replace the unit. Hope I helped.

 

[jbartos]

Suggestion: The motor shaft load needs to be checked. The motor may be disengaged and tested stand alone. Ask the motor manufacturer tech support for the motor parameters that the field test results should meet.

 

[skiier]

well.
What happened daskat?

 

[jbartos]

Suggestion: Check the centrifugal starting switch, if appliable, for its proper functioning.

 

[DASKAT]

Hey Skiier, good call on checking for overload degradation, I forgot that one. and PS I didn't do the original post.
TTFN
THE KAT

 

[skiier]

Jbartos;
Thanks for reminding me about a stuck centrifugal switch. The motor would overheat for sure. But in practise - and I have witnessed it - the motor will generally overheat in less than a few minutes. I watched a motor catch fire and keep running because of this. The house wouldn't have lasted an hour let alone the motor.

 

[Marke]

If this is a new installation, and you are in a 50Hz suply area, it is possible that the motor has been would for 60Hz and stamped 50Hz, and that the motor is effectively over fluxed. I have come across this on imported equipment. One motor ran for a couple of years before this became a problem.
The open shaft current would be high, but the motor will over heat without exceeding the nominal rating.

Best regards,

Mark Empson

http://www.lmphotonics.com

 

[jbartos]

Suggestion: Please notice that the stuck centrifugal switch is the ultimate malfunction of the switch. Less critical malfunctions are the switch improper switching with respect to the motor rpm, switch contacts are worn out, etc.