The open circuit and short circuit tests on a 4 kVA, 200 V/400 V, 50 Hz, 1-phase transformer give the following readings:
OC Test: 200 V, 1A, 100 W (with secondary open-circuited)
SC Test: 20 V, 12 A, 85 W (with primary short circuited)
a) Calculate the regulation of the transformer at full load with (i) a power factor of 0.8 lagging (ii) a power factor of 0.6 leading.
b) Calculate the efficiency at (i) half load with a power factor of 0.8 lagging (ii) 3/4th load with a power factor of 0.6 lagging (iii) the power output at maximum efficiency with a power factor of 0.7 lagging.