Electrical Engineering ⇒ Topic : Transformer On-Load

TRANSFORMER ON LOAD

The transformer is said to be loaded when the secondary circuit of a transformer is completed through an impedance or load. The magnitude and phase of secondary current /₂ with respect to secondary terminal voltage will depend upon the characteristic of load, i.e., current /₂ will be in phase,lag behind and lead the terminal voltage V₂ respectively when the load is purely resistive, inductive and capacitive.

Whatever be the load conditions, the net flux passing through the core is approximately the same as at no-load.Since the core flux remains constant at all loads, the core loss almost remains constant under different loading conditions

TRANSFORMER ON-LOAD

Figure 1 (a) shows the transformer during no-load condition. The flux (Φ) is set up in the core.When the secondary is loaded [refer to [Figure 1 (b)], the secondary current will set up its own flux (Φ) which opposes Φ. The resultant flux becomes Φ -  Φ₂. The value of e₁ will decrease because magnitude of Φ decreases. Hence ν₁ becomes greater than e₁ and primary winding draws more current from the source. Let the additional current drawn by primary be "I₂. This current I"₂ will set up its own flux (Φ₂) in the same direction of Φ and it will oppose Φ ₂ shown in Figure 1(c). The resultant flux will be Φ  shown in Figure 1(d) at any load condition if and only if

                                                             Figure (1) Transformer on load.