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# Short notes on voltage regulation, short and open circuit, transformer efficiency | EEC 213 Electrical machine

1. Write short notes on the following electrical tests
I. Short circuit test
II. Open circuit test
III. Efficiency of a transformer
IV. Voltage regulation

A. SHORT CIRCUIT TEST: The secondary is short-circuited through a suitable ammeter, A2, While a lot voltage is applied to the primary and adjusted to circulate full-load current in the primary and secondary circuit iron losses is negligible and wattmeter reading is that of copper losses in the windings [ iron loss a (flux)² applied voltage which is small about 1/30 of V1]Constant Losses: The iron loss due to hysteresis and Eddy currents are constant at all loads because Flux variation between no load and full load is 2%-5%

B. OPEN-CIRCUIT TEST: The transformer is run at the rated voltage and frequency. The ammeter (A) gives the No-load current while the wattmeter in the primary circuit reads No-load losses i.e the iron losses [ I²R or copper loss is negligible on no load since it depends on primary current which is less than 5% of full load current at no load]The ratio of the voltmeter reading V1/V2 gives the ratio of the number of turns

C. EFFICIENCY OF A TRANSFORMER: Efficiency of a transformer is the ratio of output power to the input power.
Efficiency = output power/input power
Output power/(output power+losses) = input-losses/input power

D. VOLTAGE REGULATION: is defined as change in secondary terminal voltage from No-load to Full-load and is expressed as percentage of either No-load or the Full-load value.