Author Topic: Is insulated wire a good solution?  (Read 417 times)

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Offline lighthunter

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Is insulated wire a good solution?
« on: August 02, 2021, 02:03:21 pm »
Hi all!  I am helping a friend build a complete solar power system from ground up. He is choosing to go with a homebuilt inverter. Of course will need a toroidal transformer to convert low volt DC to 120/240 AC.  When i built mine, i used multi strands of 14awg magnet wire. Some of you used conventional wire like in this photo.   

I went the magnet wire route because i didnt believe plastic coated wire would cool. Was i wrong? How is it working in real life? Has the plastic melted together and shorted out burning up your fets? Please let me know if you have any experience or thoughts on this.

(Im just talking about the low voltage winding on the outside exactly as this photo shows) courtesy of Oztules
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LH

Offline Pete

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Re: Is insulated wire a good solution?
« Reply #1 on: August 02, 2021, 05:47:38 pm »
Hi LH, I don't know about the heat of the windings, I would think that the PVC insulation would definitely keep heat in, but then it will depend on how long the inverter is being run at high power levels.
Of course magnet wire would be much easier to work with but getting it in such heavy guages would require many wires in parallel.
When I wound large electric motors and generators the wire we used was often solid fibreglass covered rectangular section.
If you were to find a motor rewinding shop nearby that did large motors they may have some on the end of a roll that you could get.
Using just one wire is probably easier to do a neat job than lots of wires in parallel, but then you are only doing a few turns if Oz's core is anything to go by.
If you work out the current capacity you want, then you can substitute any wire guages that come up to that.
I used to look up a chart that gave the sizes of the wire, and also the area in "circular mms)
So if the wire size you want is a certain area, then whatever adds up to that size in circular mm's is the go.
Often if we did not have enough rolls of the right guage I would use different guages as long as they added up to the same area.
Pete

Offline noneyabussiness

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Re: Is insulated wire a good solution?
« Reply #2 on: August 02, 2021, 09:13:36 pm »
pm Warpspeed , he the resident transformer " expert ", but he stated in the past for the " secondary " ( a few turns , 20 or so on a 48v transformer)  it is fine to run pvc insulated wire, however the " primary " he clearly stated no good for pvc insulated stuff...

Offline Pete

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Re: Is insulated wire a good solution?
« Reply #3 on: August 03, 2021, 12:49:55 am »
If you can't find anty magnet wire then you could just up the temperature rating of the PVC cable by going for
either V105 rated cable or XLPE cable.
XLPE is used a lot for mains in house electrics, it has two layers of insulation, a clear cover and a black sheath.
You could strip the black sheathing off and just use the single insulated core.
If the transformer runs up to around 100 degrees C , I would think that other components would be more likely to fail first.
Cheers
Pete

Offline noneyabussiness

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Re: Is insulated wire a good solution?
« Reply #4 on: August 03, 2021, 06:56:57 am »
i would be incredibly careful using any type of pvc based wire for a transformer... the surface of a transformer will get to say 50-60 degrees under heavy load, however if it wound tight like it needs  the centre can be well over 100 degrees , please see the reference website..

https://testguy.net/content/282-Transformer-Insulation-Classes

pvc based , waste of space aside, is unsuitable..  the temperature ratings are not sufficient,  even dangerous...

some people have used it and been successful,  but again be super careful...

Offline lighthunter

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Re: Is insulated wire a good solution?
« Reply #5 on: August 03, 2021, 08:00:19 am »
Wow, thanks for the advice guys. I have magnet wire on the shelf, i just thought i might save the guy some money as i have some 8AWG (53.4mmsq) pvc that i could use. I certainly dont want it to fail though, like Pete mentioned a while back, " usually over build, I only want to do a job once if possible.
So that settles it, magnet wire it is.  I really appreciate your experience guys!
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LH

Offline lighthunter

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Re: Is insulated wire a good solution?
« Reply #6 on: August 03, 2021, 01:23:19 pm »
The max temp of the wire is one thing but its ability to transfer heat for cooling is really the one i was worried about. I think pvc insulation would inhibit that greatly. Most 200degree wire i found is $140 for 10lbs but i found some red 150C for $100/10lbs. Or $50 for 5lbs, of 53.5mmmsq. That should do the job. Unless i find a motor to salvage. Thanks again for the advice! Thats not something id wanna learn the hard way.😁
Health Warning: May contain traces of nut!
LH