# transformer winding ratio question

• posted

I have a basic question about transformer ratios, if I have 3 windings, a pri, a sec and an aux, what's the voltage expression for each winding? My guess is

Vpri = Npri/Nsec

Vsec = Nsec/Npri

Vaux = Naux/Npri

is this right?

thanx!

• posted

I think you need to consider the voltages as well as the primaries. That is:

Vsec = Vpri * Nsec/Npri

That sort of thing. I don't think you normally calculate Vpri; I think it's what you choose (within limits of the transformer, of course). Then you use Vpri to calculate the other voltages, based on the winding ratios to Npri.

It seems to me that Vaux would be:

Vaux = Vpri * Naux/Npri

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• posted

V_pri/N_pri = V_sec/N_sec = V_aux/N_aux

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• posted

?

at

en

o catch

l.

sorry I forgot to include the voltages, I meant

Vpri =3D Vsec*Npri/Nsec

Vsec =3D Vpri*Nsec/Npri

Vaux =3D Vpri*Naux/Npri

which seems right after reading the responses, thanks

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