Transformer on Load
The transformer is said to be loaded, when its secondary circuit is completed through an impedance or load. The magnitu de and phase of secondary current (i.e. current flowing through secondary) I2 with respect to secondary terminals depends upon the characteristic of the load i.e. current I2 will be in phase, lag behind and lead the terminal voltage V2 respectively when the load is non-inductive, inductive and capacitive. The net flux passing through the core remains almost constant from no-load to full load irrespective of load conditions and so core losses remain almost constant from n o-load to full load. Vector diagram for an ideal transformer supplying inductive load which is shown below.
In actual practice, both of the primary and have got some ohmic resistance causing voltage drops and copper losses in the windings. In actual practice, the total flux created does not link both of the primary and secondary windings but is divided into three components namely the main or mutual flux linking both of the primary and secondary windings, primary leakage flux linking with primary winding only and secondary leakage flux linking with secondary winding only.
The primary leakage flux is produced by primary ampere-turns and is proportional to primary current, number of primary turns being fixed. The primary leakage flux is in phase with and produces self induced emf is in phase with and produces self induced emf E given as 2f in the primary winding.
The self induced emf divided by the primary current gives the reactance of primary and is denoted by
E = 2fπ