The distribution transformer is supplying a load at 240 V and 0.8 power factor lagging. The open-circuit and short-circuit test data are given in Example.

(a) Determine the fraction of full load at which the maximum efficiency of the transformer occurs, and compute the efficiency at that load.

(b) The load cycle of the transformer operating at a constant 0.8 lagging power factor is 90% full load for 8 hours, 50% (half) full load for 12 hours, and no load for 4 hours. Compute the all-day energy efficiency of the transformer.