SGKent
Banned
As to my general background I was highly schooled in electronics. repaired TV's, radios. many items from tube to transistor. Repair computers software and hardware for a living in an Enterprise. I no longer have test equipment beyond good VOM's at my house - but used to use many high end products scopes, wave form and RF generators etc. Only have several good high end VOM's left and maybe a DC power supply, and know how to use them. Am 61. When In highschool I built and placed well on a GE motor contest where I built a fully functional 2hp GE motor from making the windings to fully assembling it. It ran well. This motor I am working on is somewhat similar in construction having a starter switch and no brushes.
This compressor motor I am working on just sounds like it starts hard every few 1 out of 5 tries. It is not the unloader etc on the compressor. It is supposed to pull 15 amps and even on a 20 amp circuit one can tell it has a slight lag to the start and the switch sounds louder sometimes when it has that bad start. The starting cap has been replaced which helped it to start a little smoother. Motor is about 5 years old.
I took it to a local 60 year in business electric motor shop and got it back yesterday after a week. They were supposed to clean it up and then test it as it came from a cabinet shop and had sawdust in it. Cost $65 to have them check it. When I went in it had a note on it "shorted winding." I accept that might be true. I tried to ask the GM how they determined that but he was annoyed because he had been fighting with his wife on the phone before and after I dropped in to pick it up. The office staff was helpful but the arguing with his wife, probably common, had them all uncomfortable. His answer to me was very short and quite frankly poor customer service. "The oscilloscope shows it was bad." I asked how the wave form was different and all he said was "the waves are supposed to cancel out and yours didn't."
When I got home with it I pulled it apart figuring well lets see if we can see any discolored or damaged windings I have nothing to loose now. It will cost $300 - $450 to replace as it has a special base welded on it that no one but the compressor manufacture makes. The inside still was packed with some shavings, it is filthy, and the switch has some debris around it so the motor was never opened and the spade lugs are all oxidized but the motor windings all look the same clean copper varnish color with no discoloration or swelling. I know what overheated wire looks like. There also appears to be a spot where one spade lug rubbed on another insulated wire and it has left a mark so it may be arcing through the vinyl insulation there - I haven't cleaned that area yet. The armature is a laminated steel armature and there are a couple spots where the coating is bad, no rust - and one spot at the end where I can see the armature may have rubbed on the end plate or something occasionally and just lightly. Today I thought I would clean it with electronic motor cleaner, polish the switch points and regrease the bearings plus make sure nothing is rubbing. I have the special red varnish to paint any spots in the windings or armature where the varnish is bad.
The problem is that after 3 hours of reading I cannot find a reasonable article on how to test the windings with a VOM to see if there is a short to ground or between windings - and after 43 years since I built a motor I can't remember how we tested the windings back in those days. I think I can figure out a test(s) that will work but someone here must know of a really standard way to test with a VOM. I do not have a 500 - 1000 volt source to test the insulation and I am not going back to that shop to listen to him argue with his wife instead of work with a customer. For all I know I may find a staple or something - charcoalized sawdust that is someplace it should not be. They were supposed to clean it for the $65 then test but frankly I am really not even sure they wasted more than 1 minute on it to see what might be wrong. The guy's attention is not on a one time customer. Can anyone make some suggestions here to test the motor windings? It is a 120/240 motor with a running and start cap, about 15 amps. Shows up as a 1.9 and 3 hp motor in different specs. Part is Z-D20620 Marathon motor.
This compressor motor I am working on just sounds like it starts hard every few 1 out of 5 tries. It is not the unloader etc on the compressor. It is supposed to pull 15 amps and even on a 20 amp circuit one can tell it has a slight lag to the start and the switch sounds louder sometimes when it has that bad start. The starting cap has been replaced which helped it to start a little smoother. Motor is about 5 years old.
I took it to a local 60 year in business electric motor shop and got it back yesterday after a week. They were supposed to clean it up and then test it as it came from a cabinet shop and had sawdust in it. Cost $65 to have them check it. When I went in it had a note on it "shorted winding." I accept that might be true. I tried to ask the GM how they determined that but he was annoyed because he had been fighting with his wife on the phone before and after I dropped in to pick it up. The office staff was helpful but the arguing with his wife, probably common, had them all uncomfortable. His answer to me was very short and quite frankly poor customer service. "The oscilloscope shows it was bad." I asked how the wave form was different and all he said was "the waves are supposed to cancel out and yours didn't."
When I got home with it I pulled it apart figuring well lets see if we can see any discolored or damaged windings I have nothing to loose now. It will cost $300 - $450 to replace as it has a special base welded on it that no one but the compressor manufacture makes. The inside still was packed with some shavings, it is filthy, and the switch has some debris around it so the motor was never opened and the spade lugs are all oxidized but the motor windings all look the same clean copper varnish color with no discoloration or swelling. I know what overheated wire looks like. There also appears to be a spot where one spade lug rubbed on another insulated wire and it has left a mark so it may be arcing through the vinyl insulation there - I haven't cleaned that area yet. The armature is a laminated steel armature and there are a couple spots where the coating is bad, no rust - and one spot at the end where I can see the armature may have rubbed on the end plate or something occasionally and just lightly. Today I thought I would clean it with electronic motor cleaner, polish the switch points and regrease the bearings plus make sure nothing is rubbing. I have the special red varnish to paint any spots in the windings or armature where the varnish is bad.
The problem is that after 3 hours of reading I cannot find a reasonable article on how to test the windings with a VOM to see if there is a short to ground or between windings - and after 43 years since I built a motor I can't remember how we tested the windings back in those days. I think I can figure out a test(s) that will work but someone here must know of a really standard way to test with a VOM. I do not have a 500 - 1000 volt source to test the insulation and I am not going back to that shop to listen to him argue with his wife instead of work with a customer. For all I know I may find a staple or something - charcoalized sawdust that is someplace it should not be. They were supposed to clean it for the $65 then test but frankly I am really not even sure they wasted more than 1 minute on it to see what might be wrong. The guy's attention is not on a one time customer. Can anyone make some suggestions here to test the motor windings? It is a 120/240 motor with a running and start cap, about 15 amps. Shows up as a 1.9 and 3 hp motor in different specs. Part is Z-D20620 Marathon motor.
