Exam Question

(a) Describe the different type of losses occurring in the Power Transformers. (4)

(b) A single phase power transformer supplied a load of 20 KVA at a P.F. of 0.81 (lagging). The iron loss of the transformer is 200 kW and the copper loss at this load is 180kW. Calculate

(i) the efficiency (6)

(ii) if the load is now changed to 30 KVA at a p.f of 0.91 (lagging), calculate the new efficiency (6)