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QUESTION 1 A single phase step down transformer, rated 320 KVA, 4800/240 V is tested for its internal parameters. During short circuit (SC) test, secondary terminals are short circuited and a test voltage applied on primary terminals. When 200 V is applied rated primary current is measured on primary terminals and power input is measured to be 3,2 kW. During open circuit (OC) test, both terminals are open circuited and a test voltage is applied on secondary terminals. When rated voltage of 240 V is applied to the secondary terminal, current and power inputs are recorded at secondary side are 12 A and 1,6 kW, respectively. a) Using SC test, calculate equivalent series R and X of the TR referred to primary side (neglect shunt elements) (10p) b) Using OC test, calculate equivalent shunt Rand X of the TR referred to primary side (neglect series elements) (10p) c) What is the efficiency of the transformer for a load of 256 kW at 0,8 pf lagging at rated voltage? (10p) 21 = R1 +jX1 th wwm 10 In Iet Im И RAjXm3 22 = R2 + jX2 wwm 12 E E2 V2 Equivalent circuit of a transformer Zel = Rel + Xel France VSC SC test cct - ref. to primary lo Ict Rai སོ། Io Im 3jXml E Vi E2 V2 OC test cct-ref. to primary