Equivalent Reactance
MAGNETIC LEAKAGE
Till now we have assumed that all the flux linked with the primary also links with the secondary. But in practice, the permeability of the core of the transformer is finite. All the flux linked with the primary do not link with the secondary. As shown in Figure 1.29(a), ΦL1 and ΦL2 induce emf eL1 and eL2 in primary and secondary windings respectively. Therefore, in effect, we can consider it as an equivalent inductive coil in phase with the winding shown in Figure 1.29(b).
EQUIVALENT REACTANCE
If X2 be transferred to primary, let its referred value be X2′. We have
I22X2=I12X2′
i.e.,
If X1 be transferred to secondary, let the referred value be X1′ We have
I12X1=I22X1′
i.e., 
The total reactance referred to as primary (X01) is Xl + a2X2 and that of referred to as secondary (X02) is X2+. The total reactance is known as equivalent reactance. It is denoted by
X01=X1+a2X2 (1.18)
