Short Circuit Test of a 1 phase Transformer | How to perform | Learn as topper

Draw the connection diagram for the short circuit tests of a 1-φ transformer showing all the necessary instruments/meters. Describe how would you perform these tests. 

ANSWER:-

OPEN CIRCUIT TEST?

SHORT CIRCUIT TEST

The short circuit test is performed for determining the below mention parameter of the transformer.

· It determines the copper loss occur on the full load. The copper loss is used for finding the efficiency of the transformer.

· The equivalent resistance, impedance, and leakage reactance are known by the short circuit test.

The short circuit test is performed on the secondary or high voltage winding of the transformer. The measuring instrument like wattmeter, voltmeter and ammeter are connected to the high voltage winding of the transformer. Their primary winding is short-circuited by the help of thick strip or ammeter which is connected to its terminal.

The low voltage source is connected across the secondary winding because of which the full load current flows from both the secondary and the primary winding of the transformer. The full load current is measured by the ammeter connected across their secondary winding.

The circuit diagram of the short circuit test is shown below:

The low voltage source is applied across the secondary winding, which is approximately 5 to 10% of the normal rated voltage. The flux is set up in the core of the transformer. The magnitude of the flux is small as compared to the normal flux.

The iron loss of the transformer depends on the flux. It is less occur in the short circuit test because of the low value of flux. The reading of the wattmeter only determines the copper loss occurred, in their windings. The voltmeter measures the voltage applied to their high voltage winding. The secondary current induces in the transformer because of the applied voltage.

Let,

       · W_c – Wattmeter reading

       · V_2sc – voltmeter reading

       · I_2sc – ammeter reading

Then the full load copper loss of the transformer is given by

Equivalent resistance referred to the secondary side is

Equivalent impedance referred to the secondary side is given by
               

The equivalent reactance referred to the secondary side is given by

The voltage regulation of the transformer can be determined at any load and power factor after knowing the values of Z_es and R_es.

In the short circuit test the wattmeter record, the total losses, including core loss but the value of core loss are very small as compared to copper loss so the core loss can be neglected. 

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