Explain direct loading test on single phase transformer with neat circuit diagram.

Explain direct loading test on single phase transformer with neat circuit diagram. 
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1 Answer

Answer :

Direct loading test on single phase transformer with neat circuit diagram:  

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Direct loading test on transformer is carried out to calculate the losses, efficiency and voltage regulation of the transformer. The circuit diagram is as shown in figure above. Single phase supply is given to the primary of the transformer and load is connected to the secondary side. 

1) No load Operation: The rated voltage is supplied to primary winding and load is switched off. The secondary current & power is then zero. This is no load operation. The readings of voltmeter, ammeter and wattmeters are taken. The input power read by primary side wattmeter then represents the constant loss of the transformer. The secondary voltage under no-load will be the secondary emf E20. 

2) On-load operation: Few more sets of readings are taken for different loading conditions on secondary side keeping rated supply voltage. 

Efficiency and regulation can be calculated by using following formulae: 

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