Cleaning oil contamination from older electric motor

[Dranreb]

Some pics of what I found..

Dissolved insulation, I disconnected these two wires they come from the starter.
I'll be fitting new ones which shouldn't be affected by oil unlike these rubber ones.



Megger test showed a dead short on all four wires to the windings.

I then stripped off the outer sleeve of insulation from each one in turn, which were full of oil, just wiped the inner insulation clean,
then got a much better reading on three of them which was very encouraging.



The fourth one still showed a dead short, but I spotted the cause under some crud, broken insulation and bare wire.



So I will have to remove rest of the insulation from the wires and re-insulate them.
The oil will have to be removed and I'm still wary as to what to use as if it's shellac alcohol will harm that.

I'm thinking if I get a good reading when the wires are fixed I might just give it all a wipe over and leave it at that, I've seen pictures of motors still running that are clogged right up with grease and this one ran OK until a couple of days ago.

All this is new territory for me and I know almost nothing about the workings of these electrickery things but hopefully I will succeeded as I'd hate to loose this original motor, a modern lightweight one in my shaper would hurt my eyes!

Bernard

 

[John Hasler]

Some pics of what I found..

Dissolved insulation, I disconnected these two wires they come from the starter.
I'll be fitting new ones which shouldn't be affected by oil unlike these rubber ones.

View attachment 88707

Megger test showed a dead short on all four wires to the windings.

I then stripped off the outer sleeve of insulation from each one in turn, which were full of oil, just wiped the inner insulation clean,
then got a much better reading on three of them which was very encouraging.



The fourth one still showed a dead short, but I spotted the cause under some crud, broken insulation and bare wire.



So I will have to remove rest of the insulation from the wires and re-insulate them.
The oil will have to be removed and I'm still wary as to what to use as if it's shellac alcohol will harm that.

I'm thinking if I get a good reading when the wires are fixed I might just give it all a wipe over and leave it at that, I've seen pictures of motors still running that are clogged right up with grease and this one ran OK until a couple of days ago.

All this is new territory for me and I know almost nothing about the workings of these electrickery things but hopefully I will succeeded as I'd hate to loose this original motor, a modern lightweight one in my shaper would hurt my eyes!

Bernard

I think you are on the right track just wiping off the loose oil and leaving the windings alone. The only thing it does is reduce cooling efficiency a bit. You could remove the armature, wash it with soap and water, and bake it dry, but you might do more harm than good.

This sort of problem is usually caused by over-lubrication.

 

[Dranreb]

This sort of problem is usually caused by over-lubrication.

I my case it was caused by the lube oil from the drive gears dripping into the motor, which being mounted on it's side left the cooling vents in just the wrong position, if the motor had been mounted as it was designed to be oil wouldn't have got in.

This oiling (and inaccessibility) must have upset a few owners because later versions of this shaper have the motor mounted the right way up outside at the rear above the base.

Bernard

 

[hermetic]

If you clean the tails off you can slip glassfibre sleeving over them, or shrink tubing, no need to remove the tails if they are mechanically and electrically sound. Oil plays havoc with the TRS insulation on this type of motor. We used to wash motors in Carbon Tetrachloride (dry cleaning fluid) but coshh has knocked that on the head, and the recomended solvent is anhydrous alcohol. (although the comments made about it above are all correct!) the trick is to get it in there fast then blow it out before it evaporates, or it will leave the oil behind. I have done oil contaminated motors with white spirit, which does soften the varnish IF you leave it on for a long time, get it on quick and liberally, or even immerse the stator, then get it out, drain it off for a few minutes then blow dry with compressed air. then dry it out somwhere warm overnight, and megger it tomorrow. the varnish is actually oil resistant, whereas the trs tail wires don't stand a chance!
Phil
UK

 

[Dranreb]

Well it's getting a thorough warm through overnight,



the readings are slowly getting better



I stripped off the inner insulation from one wire and it was soft and crumbly don't know how far to chase this, I'll decide in the morning after testing...



Bernard

 

[hermetic]

Hi Dranreb,
that is (or looks like from your pic) VIR (Vulcanised India Rubber) with a woven cotton sheath If there is no moisture in it, and we can bet that after a night spent on the Aga there won't be, there is no point in removing the insulation, just cover it with glassfibre sleeving or shrink tubing, and tie it back to the windings in the same places it was tied before. If you test each winding with one probe on the winding wire and one on the body of the stator(I assume this is what you are testing) 50 MOhm will do for me!
Phil

 

[hermetic]

I used to have a megger like that in the 1970's, it lasted about ten years, and due to the ridiculously expensive bits of kit they are trying to sell today, which do exactly the same job, I have gone back to the Wee (windey) Megger tester. I assume you are using the Mohm setting for your test?
Phil

 

[hermetic]

OH NO! I have committed a cooker Faux Pas, its a Rayburn!!! I was looking closely to see if I could recognise the motor make, I think I can see the jigsaw joint where the stator case has been rolled round and joined, Is it an AEI or a Newman? AC Delco used that type of stator case as well, Put me out of my misery, what make of motor is it!

 

[Dranreb]

OH NO! I have committed a cooker Faux Pas, its a Rayburn!!! I was looking closely to see if I could recognise the motor make, I think I can see the jigsaw joint where the stator case has been rolled round and joined, Is it an AEI or a Newman? AC Delco used that type of stator case as well, Put me out of my misery, what make of motor is it!

Faux Pas forgiven, at least you knew the difference..

Motor make, none of the above,
here's a clue...




sorry about where it was made

I used to have a megger like that in the 1970's, it lasted about ten years, and due to the ridiculously expensive bits of kit they are trying to sell today, which do exactly the same job, I have gone back to the Wee (windey) Megger tester. I assume you are using the Mohm setting for your test?
Phil

Yep the Meg ohm setting but I noticed it was reading the same even if I pressed the button while it was unconnected! The glass is missing so I suspect a bent needle, damp or just old age...tried my dads old Baketite windey one and that was inconsistent too.

Borrowed a moderner one and got this reading



Don't like the digital, get confused by too many zeros, I like to see a needle but I hope that's OK.

Bernard

 

[Dranreb]

Chased the bad wires into the pack far as I dared and put on a couple of layers of heat shrink on everything that looked dodgy.



Got in back in the shaper, this 3/4 hp thing weighs quite a bit more than the 56 pounds my scale reads!

Must have got seasonsally confused at some point as I seem to have gift wrapped the starter thingy...



Plugged it in, apprehensively pressed the green button and :allgood:

Thanks again for your guidance on this guys, I was very nervous in case I completely messed it up and I probably would have done just that without your help.

Bernard