To ascertain / determine the followings

1. Copper loss at desired load (PC)

2. Equivalent Circuit parameters

 Equivalent Resistance R01, Reactance X01 & Impedance Z01 referred to the side in

which instruments are being connected.


Short circuit test is generally carried out by energizing the HV side with LV side shorted. Voltage

applied is such that the rated current flows in the windings. The circuit diagram is shown in the

figure. Here also voltmeter, ammeter and the wattmeter readings are noted corresponding to the

rated current of the windings.



Suppose the readings are V

noted that voltage required to be applied

for rated short circuit current is quite small (typically about 6-8%). Therefore flux level in the

core of the transformer will be also very small. Hence core loss is negligibly small compared to

the winding copper losses as rated current now flows in the windings. Magnetizing current too,

will be pretty small. In other words, under the condition of the experiment, the parallel branch

impedance comprising of R

0(HV)

and X

m(LV)

can be considered to be absent. The equivalent circuit


and the corresponding phasor diagram during circuit test are shown in figures.



Therefore from the test data series equivalent impedance namely r

e(HV)

and x

e(HV)

can easily be


computed as follows:

Wattmeter Reading =Pc =WSC = Full load Copper loss [Neglecting Iron Loss, due to reduced

voltage]