## Power Transfer in Transformer

## Power Transfer in Transformer

(OP)

I have a query -How the power is transferred from the primary winding to secondary winding in a transformer? General answer is through electromagnetic field, electric to magnetic and then to electric. But how? Can we explain this clearly so even a layman can grasp.

## RE: Power Transfer in Transformer

the secondary winding is loaded so current flows, the primary winding now sees a demand on the magnetic circuit to current flows in the primary winding as well in order to keep the working flux almost constant "it depends on the applied voltage, which is almost constant".

so, current in, current out, power in is equal to power out, preserving the energy flow.

The magnetic induction gives galvanic isolation, but two circuits are linked together, the reason is that the magnetic flux/field affects the electrons on metal atoms and give them energy to move and create electromotive force "e.m.f." then if the secondary winding is closed, a current flow.

## RE: Power Transfer in Transformer

https://en.wikipedia.org/wiki/Faraday%27s_law_of_i...

Auto-transformers operate without relying on induction. It is just one big winding with a tap or taps. They often though have a stabilizing delta, which relies on induction.

https://en.wikipedia.org/wiki/Autotransformer

## RE: Power Transfer in Transformer

## RE: Power Transfer in Transformer

Yeah, you are right. It is all self induction.

## RE: Power Transfer in Transformer

Gunnar Englund

www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

## RE: Power Transfer in Transformer

## RE: Power Transfer in Transformer

Then a question will be raised why the core size is increasing with transformer MVA? Consider 1, 10,100,1000 MVA 132/11 kV transformers. A few hundred kg for 1 MVA to 200 tons for 1000 MVA. The only difference (apart from more copper area to carry more current from extra MVA) in these units is number of turns provided for the same rated voltage. As MVA goes up, number of turns is reduced as square root of the ratio of MVA increase. So when number of turns is reduced, area has to be increased to remain with the flux density limit. E= 4.44 x frequency x flux x number of turns. The number of turns are reduced with increasing MVA to reduce the leakage flux ( that depends on NI, current x no of turns) so that leakage impedance can be reduced ( impedance varies as square of turn number) with in manageable limits(4-18 %) to avoid unacceptable voltage drops at full loading.

## RE: Power Transfer in Transformer