Multi Stand Wire in a Power transformer

[jonovid]

some youtubers are posting this mod for DIY power transformer secondary windings.
as I have difficulty in obtaining enameled copper wire over 3mm diameter. for a high current secondary.
so is it ok to use multi stand wire with insulation in a DIY 50Hz power transformer secondary?
transformer reliability?
 heating in the core?

[Andy Chee]

I would just use your existing small diameter enameled copper wire, and twist bundle it together to make DIY "Litz"wire with your required cross section.

Using conventional plastic insulated wire just isn't efficient with winding packing space, not to mention the hazards of melted insulation causing shorted turns.

[TizianoHV]

You can strip the insulation, put multiple cables in parallel, and use kapton tape to insulate the cable:


You can also use electrical tape, but it will melt at high temperatures (shorting out the transformer):

[EPAIII]

There is nothing wrong with using stranded wire in a transformer. I suspect the people who manufacturer transformers for a living mostly use solid wire due to cost and also the extra cross-sectional area that having insulation on each strand of stranded wire, which would make the transformer physically larger.

Someone probably makes some, but I have never seen a stranded wire that had the enamel applied AFTER winding the strands. There is Litz wire, but the individual strands are insulated so each one contributes to the cross sectional area.

So, if you are messing around and want to re-wind a transformer core with stranded wire, go for it. Have fun!

[coppercone2]

according to telsacoil the stranded wire has some litz like behavior despite not being insulated.


the reason is power density, stranded wire typically has thick insulation. THis means you can't get high density on a transformer. It makes sense for mass production since you can optimize materials use but for your one off so long you can reach the correct level its OK.


The other question might be insulation type. Some transformer require a very high temp insulation which is available in enamel, and PVC insulation could not meet this requirement. Teflon would, but its expensive in comparison.

The other problem might be how tight its wound, and creep with temperature. Enamel is rather hard while PVC is a sticky material. At high temp and when tightly wound the PVC insulation might kinda melt into each other and you could have some wire strands kinda creeping through the insulation to short out some turns. The thermal conductivity of PVC vs enamel also might mean that the core temperature of the transformer (i mean deep) might be higher and it could have poorer thermal dissipation.


But all these factors can be minimized and allow you to use stranded wire so long temperature is managed.


I would imagine that its maybe a single or only 2 layers of wire for this if its high current? IMO that would be fine. But if it has to be wound deep it might have issues. I am imagining rather low quality PVC insulation here.


this means power density (however you wanna call it) and peak dissipation are the most effected parameters.



Can you use teflon stranded wire ? Its available with fairly thin walls too. I think that might work a treat