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Overriding a Thermal Overload?

L

Lanse

Well-known Member
Quick question, folks...

I've got a neat little 9" Logan lathe, which I use to make bushings and such for my projects. At first it was didnt really have any issues with its thermal overload switch, then it started having some, and now it literally trips with the lathe spinning with no load on it, and while the motor is completely cool to the touch.

So, I'm guessing theres something up with the switch itself. The lathe has a 1HP 110V electric motor. Is it a good idea to override/disable/remove this thing? If so, how do I go about it?
 
Id consider repairing or replacing a faulty thermal overload device IF THATS REALLY THE PROBLEM?????????? but I wouldn't over ride it, its purpose is to protect the motor you know. I think I would place an ammeter in the circuit to see how many amps she's pulling, as the motor could have a problem and the thermal is actually doing its job and is NOT faulty!!! If its (thermal) good but still tripping out, then I suspect a motor problem, but of course, if the motors amps is within specs, the thermal could indeed be at fault.

Have you measured the voltage at the motor??? perhaps low voltage is the problem or the wiring is inadequate causing excess voltage drop???

If you measure amps and volts you have a better idea of the problem, then you can repair the motor or thermal if needed or work on the wiring if its the culprit.

John T
 
PS is it a dual voltage motor????????? If so I would try operating it at 240 instead of 120

John T
 
What is the voltage AT THE MOTOR? Voltage drop is a common cause of tripping motor circuit breakers. The greater the voltage drop, the more current the motor demands to compensate for the voltage drop, which leads to greater voltage drop and... well, you get the picture.
 
Hey lanse, do you have 3 phase power in your shop? I have a couple huge welders that are 3 phase i may be getting rid of. You in indiana or ohio? Shoot me an email glenn
 
My welder would trip the circuit breaker after about burning up half of a stick. I was going to replace the circuit breaker and found that the wires were not clamped tight enough. I tightened the screws and it has been running great since then. Check all your connections.
 
Lance,
take the motor apart and look for scratches on the rotor, which would indicate you have a bad bearing or bushing at the end where you see the scratches. Also put an amprobe on motor and see what it's drawing. Like JohnT said, if it's 110/220v the TO is a dual overload. So try 220v after you take motor apart. Sometimes motors have run and start capacitors. Check them out. Use amprobe to make sure start capacitor is being removed after a second or two.

What is the worst thing that can happen over riding thermal overload for a short time while you are there testing it will it with a probe?
 

The thermal overload was installed to prevent extended over current operation from burning out the motor.
Either the current is too high or the overload is failing and inaccurate .
 
For under $20 you can get a new HF digital probe. Mine is very accurate compaired to an old school analog. They are close enough for government work.
 
Sorry George , I know some deals are at H-F but I stick to things like rags and abrasives. Meters I buy at the electrical supply house and made in USA. Greenlee sells a nice cheap Amprobe.
 
HF digital amprobe and the free evoms are good. Been using them for years. Many other things I buy them, try to use them and return them. There are a few good things there, very few. I always save receipt and have no problem returning junk. Good thing it's close, 3 miles away and on my way in town too.
 
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