The following test results were obtained for a 20 kVA, 50 Hz, 2400/240 V distribution transformer: Open-circuit test (LV): 240 V, 1.066 A, 126.6 W
Short-circuit test (HV): 57.5 V, 8.34 A, 284 W
(a) When the transformer is operated as a stepdown transformer with the output voltage equal to 240 V, supplying a load at unity power factor, determine the maximum efficiency and the unity power factor load at which it occurs.
(b) Determine the power-factor of the rated load, supplied at 240 V, such that the terminal voltage observed on reducing the load to zero is still 240 V.