Custom transformer design parameters

[inbuninbu]

Custom transformer

I'm (slowly) getting into building a chipamp, so I'm after a toroidal transformer, 100v@50Hz to 25v, so winding ratio of 4:1.

Unfortunately, I can't seem to find any here in Japan (at least not affordable). But I figure it will be more interesting to build my own anyway!

So I've started learning more and more about transformers.

Vs/Vp = Ns/Np

This is an equation that is quite easy for me to understand. But there are so many other questions. How will the gauge of the wire affect it's characteristics? The size of the core? The material of the core? Silicon steel and enameled copper wire seem standard, but should I consider something else?

What determines heat and amperage issues?

But I can't seem to find a good resource to expound on these issues, especially in the form of equations. Any suggestions?

 

[blackice504]

Custom transformer

what current do you need?

 

[inbuninbu]

Re: Custom transformer

I'm not entirely sure yet...

I'm going to use the LM3875, which can support 55W.

So if I use 25 volts, if I'm understanding the equation

P = I * V

correctly, then I'd want around 2A for each channel, assuming I don't use more than one chip per channel.

So I guess that would make me want 5A to be on the safe side.