Help Needed - Electric Motor Problem

[countrysquire]

A while back I bought an old ACRA brand 6"X48" belt / 12" disk sander from a guy who said that it wouldn't keep running. I thought maybe it had a bad run capacitor, but it was so cheap that I'm OK even if it needs the motor repaired/replaced.

The motor is 1 HP, single phase and can be wired for 110 or 220. Turns out that it doesn't have a run cap, just a starter cap, which was bad. Also, someone had been 'working' on it and all the wires were disconnected except for those on the start capacitor. To top it off, none of the wires are marked and they don't match the colors on the wiring diagram.

I replaced the start capacitor and checked resistance of the wires to see what was the start and run coils. Connected one wire from the start and run coils to the 110v hot wire and the others to the neutral. Plugged it in, pressed the start button and it hummed but didn't turn (like you would see with a bad start cap) for about a second, then started and ran well for about three or four seconds then started 'surging' as if the phases were fighting each other. The 20 amp breaker then tripped about 10 seconds in. After double checking connections, I tried again and it started immediately, but then began to surge about five seconds in before tripping the breaker.

The only other thing that I know to check is the centrifugal switch, which looks like it might be new (hard to tell since it is enclosed). The circuit opens and closes when the switch is moved, but the springs are much stronger than I thought they would be, but that might be normal. Since it does have trouble getting started sometimes, I'm inclined to think the centrifigul switch is not the issue.

It might be that the motor itself is bad, but would like to get the opinion of others before spending money at a repair shop.

Thanks,
Bobby

 

[wyliesdiesels]

Does it spin freely with no load on it?

 

[countrysquire]

I have removed the sanding parts from both ends so that it's just the motor and there is no change. The last few times that I have started it, it has started instantly, then starts the 'surging' after three or four seconds.

 

[DeeKay]

If you're sure you have it wired correctly for 120v then I wonder if that centrifugal switch is dropping out when it's supposed to. If the start winding is staying energized it will draw a bunch of current and eventually burn up. It may already be damaged which could explain the surging and hard starting.
You can test it by disconnecting the start winding, cap and centrifugal switch. Then try to run the motor, you'll have to help it get spinning by hand. If the motor runs fine then you have a problem somewhere in the start winding, switch cap or wiring in between all that.

Post up a pic of the motor nameplate and wiring so we know what we're looking at.

 

[My Old Tools]

Sounds like its wired for 230 and running on 115.

 

[countrysquire]

Here are some photos of the nameplate, wiring diagram, and current wiring configuration.

 

[Lightning rod]

can you please check the color of the wires on the motor side to the right of the two white heat shrink pieces just above the capacitor ?

looks like someone put an extension (black wires) onto those wires (probably yellow and red)

its hard to see from the pic, what is connected to the white wire , lower right marrette?

 

[countrysquire]

Ah, it hadn't occurred to me that the two black wires might be extensions that had been added since they are in woven fiberglass sleeves (not typical heat shrink), but that's exactly what they are. One is connected to a grey wire, the other a red.

 

[nadogail]

You might want to visit a local electric motor shop with a large box of doughnuts in one hand and your motor in the other.

 

[Dagny]

turn it on and as soon as it starts remove one of the wires off the capacitor . this is what the switch does. be careful. if it works normal switch is not opening or is not wired into the start winding.

 

[Lightning rod]

so based on the connection label, the black wire that comes in from the power cord, and goes up to the top out of screen (assume to the on-off switch) and then comes down to the left upper marrette should have a grey and yellow and the white wire from the power cord should have black and red for 110v operation

it can also be flipped. white to grey and yellow and black to black and red.

I'm a little color blind and can't see the colours that great in the pic
is it connected in one of these two ways?

 

[countrysquire]

Yes, it is connected as you described in the first paragraph, and the switch is configured as you assumed. Sometimes it starts and runs for a few seconds before surging, other times it hums for a few seconds before starting to turn and ramp up speed. At this point I’m thinking that the motor does indeed have a problem so it’s time to take it to the shop.

Thanks for all the help.

 

[DeeKay]

Yes, it is connected as you described in the first paragraph, and the switch is configured as you assumed. Sometimes it starts and runs for a few seconds before surging, other times it hums for a few seconds before starting to turn and ramp up speed. At this point I’m thinking that the motor does indeed have a problem so it’s time to take it to the shop.

Thanks for all the help.

Post up what you end up finding out, I'm curious. Are there any smells from the motor?

 

[countrysquire]

No smells and doesn’t get hot, though it might not run long enough to get hot. It is puzzling that I get different symptoms on different run attempts.

 

[DeeKay]

Yeah that's kind of what's making me wonder about that centrifugal switch not dropping out every time.

 

[countrysquire]

UPDATE- I took the motor in to a shop and they found an issue with the wiring at the windings, apparently the results of the previous owner's repair attempt. Runs like a champ now.

 

[pancho400cid]

Cool! Thanks for "the REST of the story".

 

[DeeKay]

Nice! glad you got it going