# Assumptions in a ideal transformer [closed]

In a ideal transformer we assumed that there is no resistance in windings. Then why there is no infinite current in windings?

## closed as unclear what you're asking by winny, Lior Bilia, TonyM, Daniel Grillo, ChupacabrasDec 14 '17 at 7:59

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

## 1 Answer

In an ideal transformer, the winding is a pure inductor and this inductor does not have a DC component (i.e. zero winding resistance).

If you apply DC voltage (f = 0) to the windings, the reactance of the winding (inductor) will be zero due to $X_L = 2 \pi \ f \ L$ and thus the current will be infinite.

However, if you apply AC voltage (f ≠ 0), the source will see a non-zero reactance (again, $X_L = 2 \pi \ f \ L$) thus a finite-current of $i_p = V_s / X_L$ will flow through the winding.

• Furthermore, in an ideal transformer, the winding inductance is infinite, so the magnetizing current is zero for any nonzero frequency. – Dave Tweed Dec 6 '17 at 12:40