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



## jakes_66 (Jan 4, 2018)

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.


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## CluelessNewB (Jan 4, 2018)

Did you keep track of the original wiring?   

Do you have an ohmmeter?


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## markba633csi (Jan 4, 2018)

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


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## jakes_66 (Jan 4, 2018)

CluelessNewB said:


> 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.


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## jakes_66 (Jan 4, 2018)

markba633csi said:


> 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.


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## markba633csi (Jan 4, 2018)

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


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## jakes_66 (Jan 4, 2018)

markba633csi said:


> 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...


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## Blackjackjacques (Jan 4, 2018)

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.


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## markba633csi (Jan 4, 2018)

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


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## CluelessNewB (Jan 4, 2018)

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


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## jakes_66 (Jan 4, 2018)

markba633csi said:


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


Hmm, well the GFI is tripping immediately.  The rotor doesn't budge at all, just 'bam' and the GFI faults as soon as I plug it in.

Here's a sketch of the wiring.  It's crude, but should work as a sounding board.


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## markba633csi (Jan 4, 2018)

Ok well if it runs with the case grounded but no GFI then it's probably OK to use for as long as it lasts.  It may fail soon if the leakage is high, more than 30-50 milliamp or so. If your meter measures AC amps/milliamps you could take a reading from the motor case to a good earth ground (like a water pipe)
The leakage is caused by either the windings and/or the start capacitor. There may also be a small amount from particles built up around the centrifugal switch (clean the area).  You might have a hard time trying to find a replacement cap of that style, but you could mount an external cap instead.
Your sketch looks OK , the mystery connection is probably hidden in the windings somewhere by the factory.
Mark
ps the overload switch could also be leaky but not likely


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## CluelessNewB (Jan 5, 2018)

I don't understand.   You say you have *5* wires coming from the windings but your diagram doesn't show that and your note says you don't know where the "mystery connection" is.   Does that mean you really only have 3 wires actually coming from the windings?   

I would *NOT* use the motor unless you can definitively determine there is no short to ground.  The short may be internal to the flat metal capacitor in the base.   Although these capacitors were relatively reliable they are now about 60 years old.


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## jakes_66 (Jan 5, 2018)

CluelessNewB said:


> I don't understand.   You say you have *5* wires coming from the windings but your diagram doesn't show that and your note says you don't know where the "mystery connection" is.   Does that mean you really only have 3 wires actually coming from the windings?
> 
> I would *NOT* use the motor unless you can definitively determine there is no short to ground.  The short may be internal to the flat metal capacitor in the base.   Although these capacitors were relatively reliable they are now about 60 years old.



I added numbers to the diagram to show which ones lead to the stator windings.


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## Blackjackjacques (Jan 5, 2018)

jakes_66 said:


> I added numbers to the diagram to show which ones lead to the stator windings.
> 
> 
> 
> ...




What happens if you reverse the Black (Hot) with the White (Neutral?


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## CluelessNewB (Jan 5, 2018)

All of these style motors that I have seen originally had a toggle switch mounted in the base.  Could the extra wire be a remnant of the original switch?  Is it maybe running into the base and not actually into the windings? It's been a while since I worked on one of these but if I remember correctly the run winding leads were colored red & green.  Your ohmmeter is your friend.


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## jakes_66 (Jan 8, 2018)

I retested the start capacitor and it is clearly wasted.  It's reading around 3 nanofarads.    It was working before, so I tried to be very gentle with it during cleanup and painting.

I ordered a new capacitor, but now need to come up with a way to mount it.  I couldn't find anything with the right specs that would fit in the base casting like the original.  It's going to be a round 'can' type with spade connectors on one end.


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## Blackjackjacques (Jan 8, 2018)

Use the universal fastener - GE RTV clear silicone.  This method has served me more times than I can mention.


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## CluelessNewB (Jan 8, 2018)

McMaster Carr has end caps and mounting straps for the starting capacitors they sell, look to the right hand columns.  

https://www.mcmaster.com/#capacitors/=1b1gyx1


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## Blackjackjacques (Jan 8, 2018)

jakes_66 said:


> I retested the start capacitor and it is clearly wasted.  It's reading around 3 nanofarads.    It was working before, so I tried to be very gentle with it during cleanup and painting.
> 
> I ordered a new capacitor, but now need to come up with a way to mount it.  I couldn't find anything with the right specs that would fit in the base casting like the original.  It's going to be a round 'can' type with spade connectors on one end.



That sounds strange.  A reliable test I use for electrolytic capacitors is with an analog ohm meter set to Rx1K.  I first connect the leads across the cap terminals to see the meter kick up towards infinite ohms and then reduce slowly, and then reverse the leads to do the same.  If it performs as such in both directions - the cap is good.  I do not trust some of the digital handheld cap measuring devices - although my Fluke seems to be reliable.


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## Blackjackjacques (Jan 9, 2018)

jakes_66 said:


> I added numbers to the diagram to show which ones lead to the stator windings.
> 
> 
> 
> ...



Normally, the hot is fed to the protective devices like your overload switch, while the neutral is connected to the common node. But it appears from your drawing that this is reversed.  This may possibly explain why your GFCI is now tripping when before it did not - that is, if the white / black conductors have since been reversed.


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## CluelessNewB (Jan 9, 2018)

Blackjackjacques said:


> Normally, the hot is fed to the protective devices like your overload switch, while the neutral is connected to the common node. But it appears from your drawing that this is reversed.  This may possibly explain why your GFCI is now tripping when before it did not - that is, if the white / black conductors have since been reversed.



I agree with you that the hot side should feed the protection device.  I would argue that both the hot and neutral should be completely isolated from ground. If reversing the wires stops the GFCI from tripping I believe there is still an underlying problem that needed fixing.   (The problem may have been the starting cap.)


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## markba633csi (Jan 9, 2018)

Keep in mind that testing a capacitor for it's microfarad value doesn't tell you if the cap is electrically leaky to the case.  For that you do a resistance measurement from the cap terminals to the case.  Should be 0.5 to 1.5 megohm or more
Mark S.
ps didn't you say the motor would start and run without the GFI?  If so then your capacitor is OK, although it might be leaky enough to trip the GFI.  You could prove that by letting the cap dangle free from the motor and see if the GFI still trips. 
BTW,  what is the printed microfarad value of the flat cap?


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## Blackjackjacques (Jan 9, 2018)

CluelessNewB said:


> I agree with you that the hot side should feed the protection device.  I would argue that both the hot and neutral should be completely isolated from ground. If reversing the wires stops the GFCI from tripping I believe there is still an underlying problem that needed fixing.   (The problem may have been the starting cap.)


We are on the same page, and I concur, the neutral and ground should be isolated at the appliance.  However, older appliances do not always adhere to such a protocol, where the grounding conductor is also the neutral such as in the older 2-prong plug days. I have a number of such appliances, including some older vacuum tube test equipment that I have to energize through an isolation transformer because the branch circuit device is a GFCI.  The problem may very well still be the cap - but I thought that the neutral conductor feeding the thermal trip element to be a flag - especially given the report that all worked well before re-wiring, etc.


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## jakes_66 (Jan 10, 2018)

Blackjackjacques said:


> That sounds strange.  A reliable test I use for electrolytic capacitors is with an analog ohm meter set to Rx1K.  I first connect the leads across the cap terminals to see the meter kick up towards infinite ohms and then reduce slowly, and then reverse the leads to do the same.  If it performs as such in both directions - the cap is good.  I do not trust some of the digital handheld cap measuring devices - although my Fluke seems to be reliable.


The old capacitor is a flat 'sardine can' type shown in the photos.  A gentle shake yields a rattling sound... not good.  I suspect that it's internally shorted.  I wish I had an old analog meter to watch the trends as you described, but I only have this cheap DMM.  At least it has a Capacitor setting...  I should have checked for a short to the cap housing, but after getting the low capacitance measurement I went ahead and ordered a new one.






	

		
			
		

		
	
I 

The old capacitor is made by Aerovox, part number 5205028 and 124-165 MFD rating at 125VAC.  I suspect it is quite old.  I searched for a good 20 minutes online before I concluded that this style is no longer available.  The new one is the round 'can' style.



Blackjackjacques said:


> We are on the same page, and I concur, the neutral and ground should be isolated at the appliance. However, older appliances do not always adhere to such a protocol, where the grounding conductor is also the neutral such as in the older 2-prong plug days. I have a number of such appliances, including some older vacuum tube test equipment that I have to energize through an isolation transformer because the branch circuit device is a GFCI. The problem may very well still be the cap - but I thought that the neutral conductor feeding the thermal trip element to be a flag - especially given the report that all worked well before re-wiring, etc.



Thank you for the direction here.  I will reverse the black and white leads when the new capacitor arrives.  This kind of info is invaluable to me.


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## Blackjackjacques (Jan 10, 2018)

jakes_66 said:


> The old capacitor is a flat 'sardine can' type shown in the photos.  A gentle shake yields a rattling sound... not good.  I suspect that it's internally shorted.  I wish I had an old analog meter to watch the trends as you described, but I only have this cheap DMM.  At least it has a Capacitor setting...  I should have checked for a short to the cap housing, but after getting the low capacitance measurement I went ahead and ordered a new one.
> 
> View attachment 254059
> View attachment 254060
> ...



Gotcha -  and I agree, it can't be too good if you hear something rattling.   I have seen many capacitors in my life, maybe not as many as some of the more wiser folks herein, but I have never seen a cap as you show here - and your sardine can analogy is on target.  It should not make any difference if your replacement is round vice any other shape - Good luck and let us know what you learn.


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## jakes_66 (Feb 5, 2018)

Success!!!   

After some delay I was able to get the new capacitor wired up to the motor and presto.  The motor hums nicely and no more tripping the GFI.  I never did resolve why there are (5) wires going to the field windings...  However it did occur to me that these windings may have been designed for dual voltage, just wired this way for my application.

Now on to drum switch.  It's an older Dayton model 440X I think...  I bought it used and just pulled the cover to find that only (4) of the (6) contact fingers are in place.  I'll have to dig up some more.

Thanks for all your input.  Looking forward to finishing this restoration!

-Jake


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