Multi-winding transformers...?

Question

In an ideal, 100% efficient transformer with a single primary and a single secondary winding, the general relations are:
Vp*Ns = Vs*Np (voltage stepping relation)
Vp*Ip=Vs*Is, (power relation)
where V are voltages, I are currents, N are coil turns, and p and s are subscripts identifying the primary and secondary coils, respectively.

How are the general relations modified in the case of multiple secondary windings?

Answer 1

The same formulas apply. Treat each secondary winding like a separate transformer (with the primary) to determine voltage and power in the secondary.

The total power in the primary will be the sum of all the secondary powers (using your power relation formula).

As for efficiency, there is generally no major 'hit' to efficiency in a multi-secondary transformer.

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