- 5. A 5 kVA, 1 transformer has a core loss of 40 W and full load ohmic losses of 100 W. The daily variation of load on the transformer is as follows 7 am to 1 pm 3 kW at 0.6 p.f. 1 pm to 6 pm 2 kW at 0.8 p.f. 6 pm to 1 am 1 am to 7 am 6 kW at 0.9 p.f. No load Determine the all day efficiency of the transformer. 6. A 2200/400 V, 1- transformer has the following resistances and leak- age reactances: r = 1.2 2, r2 = 0.3 2, x1 = 4.00 2, x2 = 1.00 2 A load of resistance 42 and inductive reactance 3 2 is connected across the secondary terminals. Calculate the load voltage, load power factor and power consumed by the load. 7. A 33 kVA, 2200/220 V, 50 Hz 1 - transformer has the following pa- rameters: Primary winding (HV side): r = 2.4 2, x = 6.00 2 Secondary winding (LV side): r2 = 0.03 2, x2 = 0.07 2 (a) Find the equivalent resistance and equivalent reactance referred to (i) primary winding and (ii) secondary. (b) calculate the total ohmic loss at full load. (c) Calculate the voltage to be applied to the HV side, in order to ob- tain a short circuit current of 160 A in the LV winding. under these conditions, find the power input also. 8. A 10 kVA, 2500/250 V, single phase transformer has resistances and leakage reactances as follows: T = 4.80, r2 = 0.048 2, x1 = 11.2, 2 = 0.112 Subscripts 1 and 2 denote high voltage and low voltage windings re- spectively. With primary supply voltage held constant at 2500 V, calculate the secondary terminal voltage, when (a) the LV winding is connected to a load impedance of 5+ j3.5 N (b) the transformer delivers its rated current at 0.8 p.f. lagging on the LV side. 9. A 20 kVA, 2500/250 V, 50 Hz, single phase transformer gave the fol- lowing test results: OC test (on LV side): 250 V, 1.4 A, 105 W SC test (on HV side): 104 V, 8 A, 320 W Compute the parameters of the approximate equivalent circuit referred to high-voltage and low-voltage sides. Also draw the exact equivalent circuit referred to the low-voltage side. 10. A 200 kVa, 11000/400 V, delta-star distribution transformer gave the following test results: OC test: 400 V, 9 A, 1.50 kW SC test: 350 V, rated current, 2.1 kW Calculate the equivalent circuit parameters referred to the HV side and its efficiency at half full load of unity power factor.