Craftsman 1/2HP motor, 5 wire field windings?

[jakes_66]

I've been slowly finishing up a restoration of a 12" Atlas QC54 and have hit a snag. The electric motor was tested before I started the restoration, but now trips the GFI. I did not disassemble the motor for the restoration, just a paint job since it seemed to work great. So now I disassembled it for diagnosis, but can't figure out why there are (5) wires leading to the field windings??? I understand that the (2) smaller yellow wires are for the start-up windings, but there are (3) larger wires for the run windings... Why (3)??!! It's a 115V single phase reversible 1/2HP Craftsman motor that I would bet was original to the lathe.

Why are there (5) wires??? Shouldn't there be just (4), (2) big wires and (2) small wires???

I have an impulsive need to understand before I can make a repair. Thanks for your help.

 

[CluelessNewB]

Did you keep track of the original wiring?

Do you have an ohmmeter?

 

[markba633csi]

Same questions I was going to ask- first rule is to label everything before/during disassembly
Can you re-create the original hookup? If not we will have to do some continuity tests; I see you have a meter there
Mark
ps I see a drum switch back there was that installed? Also, where is the start capacitor? I don't see it

 

[jakes_66]

Did you keep track of the original wiring?

Do you have an ohmmeter?

Wiring it back up is not a problem. I have a photo on my phone showing how it was originally wired, taken before I disassembled (see below). I do intend to install the drum switch and make it reversible by wiring the startup windings to switch polarity.



I just don't understand why there would be (3) leads for the main windings.

 

[jakes_66]

Same questions I was going to ask- first rule is to label everything before/during disassembly
Can you re-create the original hookup? If not we will have to do some continuity tests; I see you have a meter there
Mark
ps I see a drum switch back there was that installed? Also, where is the start capacitor? I don't see it

The capacitor is still wired in to the circuit. You can barely see the end of it peeking out under the motor base in the 2nd photo of the original post.

 

[markba633csi]

I see the cap it's a flat style. I think the 3 wire puzzle will become clear if you can make a diagram of the internal motor wiring-including the cap
So all you did (before disassembly) was to paint the motor and then it started tripping the breaker? If so then I would check resistance from all motor wires to the case. GFIs trip if there is leakage to ground or a direct short to ground.
Did you have a ground wire on the motor when you tested it?
Mark

 

[jakes_66]

I see the cap it's a flat style. I think the 3 wire puzzle will become clear if you can make a diagram of the internal motor wiring-including the cap
So all you did (before disassembly) was to paint the motor and then it started tripping the breaker? If so then I would check resistance from all motor wires to the case. GFIs trip if there is leakage to ground or a direct short to ground.
Did you have a ground wire on the motor when you tested it?
Mark

I'll see if I can make a sketch, good idea. Also, the original plug I used to test was ungrounded. The motor ran fine using that plug.

Now I've replaced the wiring from the plug to the motor and added a ground. I just put it under one of the screws that attaches the bottom cover to the case. Since it's tripping the GFI, I have voltage getting to the case somehow. I opened it up to test continuity from the windings to the case and found the extra wires...

 

[Blackjackjacques]

The circuit feeding the motor need not be a GFCI. Does it trip when you connect it to a non-GFCI circuit? Motors, especially old motors can cause an excess leak to ground - especially if you paint it, spray it with WD 40 etc. GFCIs trip time according to the following formula:
T=(20/i)^1.43 where T is in seconds and i = mA. So a 5 mA leak can take as long as 7 seconds to trip.

 

[markba633csi]

Jacque beat me to it- the motor may have enough "normal" leakage such that using it with a GFI is not possible.

 

[CluelessNewB]

Are two of the winding wires attached to the same terminal?