Motor Running Hot

Charles Spencer

Charles Spencer

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We had our Memorial Day cookout yesterday because rain was forecast for today. My son-in-law was over with my daughter and grandkids. He had asked me about a wood turning lathe before because I have one set up and about three or four more in various states of disassembly. So I showed him an old PowerKraft lathe and some chisels, centers, documentation, safety glasses, etc. Everything he needed besides a chuck and a motor. And I told him where to get the chuck and that I might have a motor for him.

My SB 9A has a 1/3 hp GE motor. I have a 1/2 hp GE motor that I was going to replace it with. So today I hauled the 1/2 hp motor out, lubricated it, and ran it for a bit. It seemed to be working fine. It also was connected to a drum switch and ran in reverse, which my current motor didn't do. Off came the old motor. Now I have finally learned to check things out if I can before I install them. So I ran the motor forwards and backwards for about 10 minutes. It started smoking but I knew that it was just burning oil. I figured I had gotten a little sloppy and it was just excess burning off.

Well it wasn't. After I ran it some more I decided to look in the gits. They were really hot. I got my non-contact thermometer out. The case of the motor was over 200F and the inside of the motor was over 400F.

Anyway, I left it on the work bench with a fan on it to cool off. It was too hot to mess with. I'm guessing it might be some kind of bearing problem. But I figured I'd have a beer and ask all you folks if you have any ideas.

The particulars from the data plate are:

Model: 5KC63AB776
Type: KC
PH: 1
HP: 1/2
CYC: 60
Amp: 7.0
Volts: 115
RPM: 1725
Temp Rise: 50 degrees C.
GEJ: 1404
Time Rating: Cont.
Locked KVA per HP: K

I'd appreciate any insights that you can give me.


PS: I found this thread on the Home Machinist forum:

http://www.chaski.org/homemachinist/viewtopic.php?f=42&t=93067
 
Pick a direction and direct connect without the drum switch. I'm guessing something is wrong in the switch. Maybe connected wrong or bad contacts.
 
could be a bad capacitor or starter contacts stuck on...
 
Give the end bell a tap with a hammer and it might knock the switch loose. I didn't think of the capacitor but I think it would have problems starting. Switch makes sense.
 
Most likely the starter contacts were stuck closed. Hopefully you shut it down before any more permanent damage was done.
 
Do a bit of deductive reasoning here, I suspect that this is a 110 VAC, 1 phase induction motor?

Ask yourself "what did I not do that could cause such a condition"?

Did I supply electricity, this is true because it actually rotated under power.

Is it a dual voltage motor? many small motors are 120/240 and must be wired accordingly. If the data label is unreadable or missing then a clue would be the number of existing wire connections, how many connections are needed to operate a 110 VAC single phase, single voltage, single direction induction motor? Four at most, if there are 6 or more leads it is likely dual voltage or has more then one speed.

Did the motor start when I turned on the switch? True, this rules out the start capacitor and switch, if either had failed it would never have started by itself.

Does the motor have a run capacitor? This may be difficult to detect by mere observation but the cover that protects these devices will be rather large often housing both start and run capacitors.

I received this motor from a friend/scrap pile/Ebay/ditch alongside the road? On occasion some proprietary equipment rears it's ugly head and is released into the wild.
As a very generic example if XYZ Giant Home Appliance Corporation contracts the ABC Enormous Electric Motor Company to make 1,000,000 1/2 HP motors this year for the newest model I-Dryer/I-Trash Compactor.

I have just Trademarked the name I-Trampactor™, I am way ahead of the curve, also Steve Jobs has the ability to file lawsuits from the grave. Have also Trademarked a device called The Abdicator™, this will give a 20 year old person the abdominal muscles of a 50 year old thereby saving 30 years of painstaking labor and beer.

I digress, sorry about that, this was about electric motors was it not?, These may look the same yet can be wildly different as the Ginormous Annoying Appliance Corporation Of America will only buy them for $9.00 each
 
Wreck™Wreck said:
Did the motor start when I turned on the switch? True, this rules out the start capacitor and switch, if either had failed it would never have started by itself.
Click to expand...

I agree about the capacitor but not about the switch. If the switch had failed open, the motor would not start but if it fails closed, the motor will start and run hot (eventually burning up the start winding).
 
a bad run capacitor will make it run hot...just like bad timing on a car
 
Do nothing...zip nada.

Wait until quiet and cool.

Turn switch on with it unplugged.

Now plug in while ear close to motor and LISTEN.

After it spins up unplug and let it slow down.

Yiu may not hear the starter switch on start but on power off it should click upon slowing down.

No noise means stuck switch or no switch but most have one.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk
 
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