Electrical Engineering ⇒ Topic : Leakage Reactance

LEAKAGE REACTANCE

In ideal transformer, we have assumed that all the flux linked with the primary winding also links with the secondary winding. For an actual transformer, the flux does not remain in magnetic core, i.e., all the flux linked with primary does not link with the secondary winding. As shown in Figure (a), a part of it, i.e., Φ_L1 completes its magnetic circuit by passing through air. This is called primary leakage flux. The Φ_L1  links only with primary turns and induces an e.m.f. e_L1 in the primary winding. Similarly, secondary ampere turns (m.m.f.) sets up leakage flux Φ_L2 which is linked with the secondary turns and induces an e.m.f. e_L2.

                                                          figure (a) Leakage flux

The leakage flux in each winding produces a self-induced e.m.f. in that winding. In other words, we can say that it is equivalent to an inductive coil in series with each winding. It can also be said that a transformer with magnetic leakage is equivalent to an ideal transformer only if the leakage is depicted by equivalent inductive coils both in primary and secondary windings. This is shown in Figure (b).

                                                              figure (b)   Winding reactance

In Figure (b), the parameters X₁ and X₂ represent leakage reactances of the primary and secondary windings