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Post by Travis on Jul 26, 2018 17:23:14 GMT
I wanted to create a thread that just deals with having a motor rewound. It's here under DR simply because I don't recall anyone having a CA or CK rebuilt to this level.
I reached out to Eurton and explained what we were doing. They've rewound motors for John Higdon, Kevin, me and soon for Garrett.
They suggested that 200 C was good and much higher than original, but gave me the option of 240 C at an additional cost. The additional cost is primarily due to special wire being ordered. It's roughly a 50% upcharge.
$365 vs $550
Maybe it's overkill, but we don't want to open these things again.
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Post by elec573 on Jul 27, 2018 5:45:16 GMT
Thanks for posting Travis! I think it’s a good topic to explore. Have any other company’s been used ?
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Post by Travis on Jul 27, 2018 6:22:15 GMT
Herb,
I haven’t felt the need to explore options on this. I don’t enjoy explaining to various companies what I’m wanting. I figure it’s easier for one company to be a bit familiar with the issue.
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Post by birkie on Jul 27, 2018 13:09:49 GMT
I suspect 200C would be OK as well. That's almost 400F. Mineral oil breaks down at 350F, so I suspect that if it ever actually got that hot, the dome would need to be opened anyway!
Psychologically, $365 seems low enough that it's almost worth it to re-wind without a second thought.
That being said, I don't know a lot about motor winding. The internets say that that there is a doubling of life for every 10C below the limit it operates below the rating, and the rating is designed for 20,000 hours of life. For the typical duty cycle of the DR of 30-33%, that's about 7 years if it truly ran at 392F with the cheaper wire. If it ran at 300F (which I still feel is high, but who knows - the DR windings seem to look crispy), then it's about 2^5 or 32x the rated life, or about 224 years of operation at a typical DR duty cycle. If it ran right around the mineral oil breakdown limit (who knows - maybe the black crud is cooked mineral oil), then that would reduce it to about 36 years. 240C rated wire would last 16x longer than however long the cheaper one lasts.
There's a place in Harrisonburg (just 15 minutes away) that was highly recommended by the folks who sold me the R124, so I'm going to chat with them ar some point about the possibility of re-winding.
The mention of re-wiring a CK (which nobody has done?) is interesting. I read in the GE archives that (I think in one of the "Ask Steenstrup" papers) that the oil cooling of the windings relies on the oil wicking through the cotton insulation of the windings. In a modern re-wind, that won't happen. So there's a chance that a CK would be thermally worse off with a rewind.
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Post by turbokinetic on Jul 27, 2018 13:20:56 GMT
I wanted to create a thread that just deals with having a motor rewound. It's here under DR simply because I don't recall anyone having a CA or CK rebuilt to this level. I reached out to Eurton and explained what we were doing. They've rewound motors for John Higdon, Kevin, me and soon for Garrett. They suggested that 200 C was good and much higher than original, but gave me the option of 240 C at an additional cost. The additional cost is primarily due to special wire being ordered. It's roughly a 50% upcharge. $365 vs $550 Maybe it's overkill, but we don't want to open these things again.
I don't pretend to be a motor rewinding expert but I do have a couple thoughts to add to this. Many of us Made in USA people have a hard time grasping how hot a temperature of 200 or 240°C really is.
200°C = 392°F 240°C = 464°F
If you've ever accidentally touched the racks in your oven while removing a cake, at 350°F, you know this is orders of magnitude hotter than a compressor motor would get.
It's hard to compare the performance of cotton insulation to a modern coating, when it's inside a compressor. Cotton supposedly ignites around 400°F, in a normal atmosphere. If there is a lack of oxygen, this would preclude actual flaming, but that's not to say the cotton would not become brittle, release vapors, or fail in some other manner.
In my educated opinion, there is more than likely some other reason a few rewinds have failed; other than generalized overheating of the winding insulation. It seems like there could be mechanical, or possibly chemical attack factors coming into play.
Once there is a short circuit (due to any reason) there will be localized overheating, so it's easy to see the results of this and jump to conclusions.
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Post by Travis on Jul 27, 2018 18:17:34 GMT
I took the liberty of sending a picture of Kevin's new DRA2 stator to Eurton to ask about it. I think the green stuff is epoxy holding the insulation. I am not sure if it was dipped. My DR3 was rewound twice. The local shop in town tackled it and made a mess out of the dipping. They also left me with four leads so that I could change the rotation. I was concerned that the dipping would plug the system and sent it to Eurton. I think all Eurton did was to clip the fourth lead and clean it up more. Kevin got a nicer looking stator. I am attempting to learn what we want and how to request it. I have three units that have failed and are special. The original windings fail due to heat, movement and general deterioration of the cotton. It just gets rotten. It would just take a little wear in one area and you've got a failure. I suspect that by using modern materials, even 200 C with R124 and living in a conditioned space, even a problematic DR would last a long time. I would likely go the 240 C wire for the DR3 and use the 200 C wire for the DR2. It's quite obvious to me that the larger units work harder. Attachments:
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Post by joneske on Jul 27, 2018 19:16:13 GMT
Thanks for posting that Travis. They did 200 C and charged me $395 plus about 70 bucks for shipping both ways. That seems reasonable to me for quality work.
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Post by birkie on Jul 28, 2018 14:20:47 GMT
My DR3 was rewound twice. The local shop in town tackled it and made a mess out of the dipping. They also left me with four leads so that I could change the rotation. Do you happen to have any pictures of that messy rewind job, for educational purposes?
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Post by elec573 on Jul 29, 2018 5:02:47 GMT
That doesn’t look like it was dipped, just rewound to me . But they should have said how or what they did . Hopefully there ‘s no problems with it . Temperature is going to be the make or break point over time.
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Post by Travis on Aug 4, 2018 2:48:56 GMT
I spoke to another MT buff in PA today. He suggested I speak to a local shop about rewinding motors. It seems he's got a shop that is knowledgeable and does care.
I am not trying to be fussy, but I'm very interested in getting a better understanding about the best materials for this application.
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Post by elec573 on Aug 4, 2018 3:54:26 GMT
Well this is a good subject. It would be nice to have one place to send our motors to get rewound , that knows and understands our special needs. There are some motor shops in my area perhaps I we’ll inquire and see what they say .
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Post by Travis on Aug 21, 2018 14:13:14 GMT
Huntingdon electric has received the stators from Gill. I just called them to explain what they have. I also followed up with a detailed email about what we think we know. They will evaluate them and give me a quote.
I suggested that these fail because of age, deterioration of the insulation, exposure to so2 and heat. I am suspecting that heat is the biggest issue, but the other three play a part.
I sent the winding specs, pictures of the motor assembled and a picture of a DR refrigerator for reference.
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Post by joneske on Aug 21, 2018 15:12:40 GMT
Huntingdon electric has received the stators from Gill. I just called them to explain what they have. I also followed up with a detailed email about what we think we know. They will evaluate them and give me a quote. I suggested that these fail because of age, deterioration of the insulation, exposure to so2 and heat. I am suspecting that heat is the biggest issue, but the other three play a part. I sent the winding specs, pictures of the motor assembled and a picture of a DR refrigerator for reference. What made you decide to not use Euroton?
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Post by Travis on Aug 21, 2018 15:33:39 GMT
I am open to using Eurton, but the recommendation of Huntingdon by someone that had a 100 yr old armature rewound got my attention. I would like a good understanding of the wire class, dipping and lead wire composition. I get frustrated with tradesmen that say "we got it" but maybe they don't. I have to admit, the only two people I trust to make that claim are Gill and Doug. They got it!
I figured this would be a good second opinion, if nothing else. I am very impressed with the DRA2 stator they did for you.
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Post by Travis on Aug 30, 2018 19:21:34 GMT
I received the quote from Huntingdon, $438 to rewind, dip and clean each stator. I asked what wire class and they said H, rated for 180C(356F) it seems. Birkie felt that would be ok. Garrett said ok, if we did. God, it's a great thing to have a mini DR team in your phone. None of this would be possible without the contributions of many, most importantly the guy with two stink bombs in his garage.
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