Transformer Winding Convention - Dual Primary?

[Adipocere]

What is the typical way to wind dual primaries for 120v/240v operation?
First part in several layers and then second part?
Alternating layers of first and second parts?
Bifilar?
Something else?

 

[AndrewT]

I think they are bi-fillar. Hopefully Tony, or some other Member sees this.
That puts the full 120Vac across the two layers of insulating enamel.
You really must be sure that the enamel is not damaged by your handling and winding procedures.

For a home wound primary I would be tempted to go for two separate windings with each layer insulated from the lower layer to give some confidence in holidays not shorting out your primary.

But, I would never attempt to wind a mains primary, simply because I can't accept the risks involved. Would my insurance company pay out if my house burnt down?

 

[DF96]

Definitely not bifilar or alternating, as you need to maintain good insulation between the two primaries. Either first part, then insulation, then second part, or side-by-side with insulation between.

Just my guess as I am not a transformer expert! I would personally never attempt to wind a mains primary as I know I don't know enough to do it safely and reliably.

 

[TonyTecson]

i would not recommend bifillar, although i have done an isolation type 230volt ac transformer using #16 magnet wire on a 1.75 inch core stacked to 3inches and still in service to this day after more than 5 years, i am still using it......this is one of those, don't do this at home thingy....

one after the other and with proper insulation is the way to go.....

 

[Adipocere]

Thanks guys.