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Motor thermal switch

DPittman

DPittman

Ultra Member
Newly acquired lathe and I am going through it thoroughly.....the motor will run for about 15 minutes and then it shuts down and won't start again u til it presumably cools. The motor just hardly gets warm. I am electrical challenged and so all I can do is guess and ask for help. Do bad capacitors act funny this way when they go bad? I'm guessing the problem is in the motor somewhere but is it likely it could be in the electrical panel (gosh I hope not).
See picture of panel.
20220525_171220.jpg
 

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Can you get a picture of the motor data plate? (Voltages, amps.) What voltage are you running the motor on? I would guess that dial marked "6.8 9 11" is the overload protection and the blue square post will reset it.

WAG: If the motor was changed from 230 to 115 volt supply, it will require twice the amperage to run. The overload protection may not have enough range to allow for the higher amperage.

Craig
 
trlvn said:
Can you get a picture of the motor data plate? (Voltages, amps.) What voltage are you running the motor on? I would guess that dial marked "6.8 9 11" is the overload protection and the blue square post will reset it.

WAG: If the motor was changed from 230 to 115 volt supply, it will require twice the amperage to run. The overload protection may not have enough range to allow for the higher amperage.

Craig
Click to expand...
I can't quite get at the data plate without dropping the motor. I believe the motor is the original and has always been 240.
 
Up the range a bit and see what happens.

Also if you have a clamp meter check the actual amps motor takes.

This does happen if someone played around with voltage - you really need that motor plate & you really need to make sure that all is at 240v 1ph.
 
I agree that you need to get at the motor plate and you need an amps reading.

What happens if you run it without the belt (ie no load at all)?
 
It would appear that the lathe is wired single phase? The controls are for a 3 phase. The blue “reset”. Would need to be pushed if the thermal tripped. If you are running single phase, is the the centrifugal switch working? If it is staying on- might explain your issues
 
Couple of other things, some one may have played with the little red knob (tech term ;)) this is resettable fuse link. These things also get tired and start tripping early.

My guess is not the motor but the something in the controller that a little tired.
 
So I'm pretty confident the motor and wiring has not been fiddled with since new other than the stop/on push button switch on the panel has been replaced with a keyed on/off.
Yes I am running single phase 220 volt.

I have a video of the control box when it kicks off after about 15 minutes of free running. Motor is just slightly warm. When the lathe kicks off you will see the gizmo (breaker?) in the top left corner pop and the gizmo in the top right corner (magnetic contactor?) do its' thing.

After a few minutes (maybe 5?) everything seems to reset itself and it will start up again.

I believe if im not mistaken the centrifugal switch is in the motor and is for starting? I have not had the motor appart yet.

What does the red dial adjust?

 
My you tube is not working but the red dial “should” adjust your thermal trip - so if you run the motor over the amp setting it will trip once the bimetal strip heats

If your lathe is running single phase - that chinesium transformer is ??? 220 v to 110v ?

Make sure the capacitors on the motor are connected and nothing is interfering with the centrifugal switch (need to open back of motor)
 
Brent H said:
My you tube is not working but the red dial “should” adjust your thermal trip - so if you run the motor over the amp setting it will trip once the bimetal strip heats
Click to expand...

Mine doesn't work either. Source NFG?
 
DPittman said:
Hmnn don't know what's up with that? It appears to be working from this end both in youtube and the thread for me.
Click to expand...

Might be a phone thing.

I hardly ever use a computer anymore. I just use Chrome on my phone.

When I click your video, I get all kinds of videos but not yours.
 
Well that's interesting. Does my video thumbnail of the control panel box show in your thread? It does on mine.

I can only imagine that it was likely something I did wrong, but I "thought" I did everything the same as other successful posts.
 
Brent H said:
My you tube is not working but the red dial “should” adjust your thermal trip - so if you run the motor over the amp setting it will trip once the bimetal strip heats

If your lathe is running single phase - that chinesium transformer is ??? 220 v to 110v ?

Make sure the capacitors on the motor are connected and nothing is interfering with the centrifugal switch (need to open back of motor)
Click to expand...
That is correct, but if they set at the limit, they tend to wear (not the best word) and start to trip earlier than required. Once this starts, it only gets worse with time and has nothing to do with the motor being the cause though it may seem like it.

Based on the fact that the motor starts without fail when cold and shuts off after a period of time. I'd bet that this is what needs replacing.
 
DPittman said:
Well that's interesting. Does my video thumbnail of the control panel box show in your thread? It does on mine.

I can only imagine that it was likely something I did wrong, but I "thought" I did everything the same as other successful posts.
Click to expand...

Yes, the thumbnail shows up.

But when I click on the video, I get a different video.

I doubt you did anything wrong. Browsers, webpages, and a bunch of other web access programs have to figure out what they are being asked to be displayed on and then have to modify themselves to play in that way. It's a big mess and getting worse as the number of possible combinations keep growing. I find it amazing that anything works!
 
I had a similar problem with a new BusyBee mill. It would shut down after about 20 minutes.
I let it cool down for a while and restarted it and it was good for another 10 minutes and shut down again.
A contacted BusyBee and was told to disconnect the power and remove the cover from the control and
tighten all the connector screws. Some of them were quite loose. 13 years later it has not missed a beat.
 
terry_g said:
I had a similar problem with a new BusyBee mill. It would shut down after about 20 minutes.
I let it cool down for a while and restarted it and it was good for another 10 minutes and shut down again.
A contacted BusyBee and was told to disconnect the power and remove the cover from the control and
tighten all the connector screws. Some of them were quite loose. 13 years later it has not missed a beat.
Click to expand...
Good idea thanks. That's electrical work I can do!
 
DPittman said:
Good idea thanks. That's electrical work I can do!
Click to expand...

It's great advice. I've said this here before.

After 35 years working on automotive and electrical/electronic systems, I came to understand that the number one electrical problem by a VERY WIDE margin has always been the connections. I have a saying "connections connections connections - check the connections!"
 
Well I decided to fiddle with the red dial thingy (thermal switch?) and I cranked it down to the 6.8 setting and it ran for maybe 5 minutes and it shut down. So I then tried turning the other way to "11" and it has ran for 40 minutes now and all seems good. There seems to be more adjustment room to go higher yet but I will leave it there as I suspect it will be fine now.

Thanks everyone for your input.
 
DPittman said:
So I then tried turning the other way to "11"
Click to expand...
Um, you really need to check the motor tag. The overload control exists to protect the motor from going up in smoke if it is...well...overloaded. I assume the "11" means that the overload control will pass up to 11 amps for an extended period of time. If your motor is rated for less than 11 amps, you risk overheating and destroying it. Even potentially causing a fire.

BTW, 11 amps at 230 volts is more than 1.5 horsepower for a typical AC induction motor. A motor could start pulling more than amps than it used to if, say, the motor bearings are shot. The extra draw would be because of increased friction. But there could be other problems, like poor connections* that were already pointed out, or even a combination of problems.

Craig
* The resulting arcing can also be a fire risk.
 
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