Give answers quickly
4. (a) What is the purpose of short circuit and open circuit test of a transformer? Briefly describe the procedure for short circuit test with necessary diagram. [3+5]
b) A 120-VA 130/13 V transformer is to be connected so as to form a step-up autotransformer. The conventional two-winding transformer has series resistance and reactance of 1% and 8% per unit respectively. A voltage of 120V is applied to the autotransformer's primary. Calculate i) secondary voltage of the transformer, ii) Rating advantage in autotransformer mode of operation. iii) Series impedance per unit in this mode of operation [2+3+2]