Electric motor surging and popping the breaker

[MushCreek]

Did I kill the motor in my stationary belt sander? It's 120V, single phase. I was working it hard the other day when it stopped. I turned it off, then back on. It ran, but was surging and soon popped the breaker. Tried it again a couple hours later and it was the same. I've never heard a motor surge before. Did I kill it? Maybe just a blown cap?

 

[FrankLee]

Did I kill the motor in my stationary belt sander? It's 120V, single phase. I was working it hard the other day when it stopped. I turned it off, then back on. It ran, but was surging and soon popped the breaker. Tried it again a couple hours later and it was the same. I've never heard a motor surge before. Did I kill it? Maybe just a blown cap?

If the breaker tripped, my swag is that the windings overheated and burned out. Any burning smell or smoke? Is there a manual thermal switch?
It's not the capacitor. The start cap is removed from the run circuit at start-up.
What brand of motor?
Does the rotor turn freely by hand?

 

[PCustoms]

Did I kill the motor in my stationary belt sander? It's 120V, single phase. I was working it hard the other day when it stopped. I turned it off, then back on. It ran, but was surging and soon popped the breaker. Tried it again a couple hours later and it was the same. I've never heard a motor surge before. Did I kill it? Maybe just a blown cap?

What were you sanding?

What do you mean by surging? Does it spin free when it's off?

 

[BillK]

Is it full of wood or metal dust ? I have a smaller belt sander at my business and every one in a while it starts slowing down and I have to take the air hose and blow out the motor real good. That usually revives it

 

[PCustoms]

Is it full of wood or metal dust ? I have a smaller belt sander at my business and every one in a while it starts slowing down and I have to take the air hose and blow out the motor real good. That usually revives it

This has got mine more then once.

 

[MushCreek]

I'll have to take the covers off to get a better look. No burning smell or magic smoke. I was grinding some welds down on steel.

 

[WillyBoy]

Did you slow the motor down enough to have the centrifugal switch energize the start winding?
Opening and closing that switch multiple times while the motor is trying to maintain speed can cause the capacitor to fail.
It's also possible to overheat the start winding to the point that it fails.

The surging could be the start winding being de-energized at close to full speed and the run winding not keeping the motor running. Then it slows down and the start winding gets energized again. Maybe.

 

[PCustoms]

I'll have to take the covers off to get a better look. No burning smell or magic smoke. I was grinding some welds down on steel.

Blow it out!

 

[MushCreek]

Okay, the motor is a 1-1/2 hp 'compressor duty', which to me says it's a cheapo. I removed the sanding belt, and it ran fine. A 6X48 sander has a pretty good load on it just driving the sanding belt. I put the belt back on and tightened it gently. Seems to work OK; I haven't tried actually sanding anything yet.

 

[WillyBoy]

I hope it's OK. A long time ago I killed a bench grinder with a wire wheel mounted by trying to work it too hard, bogging down the motor repeatedly until one of the windings "gave up".

 

[MushCreek]

I used it today, and it ran, but it seems like it's not as powerful (or I'm being more cautious).

 

[fitter30]

Might want to pull the end bells blow out windings and centrifuge switch could be packed with saw dust.

 

[MushCreek]

Yeah, I'm wondering if running it for a few minutes with no load blew out whatever was in there. My belt sander is missing the cover for the base, so a propped a piece of plywood against it. Sure enough, when I was grinding steel, it covered the plywood panel with dust. I imagine a lot of it was going in there. Next time I have a few hours to kill I'll take the motor out and clean it up. I'll make a proper cover, too! I also feel that a 1-1/2 hp compressor duty motor is barely enough for a 6 X 48 sander, especially grinding steel. It should have had a full 2 hp motor. It's an old Powermatic, and I know that the motor isn't factory.