Normally Supply voltage is applied on ___________ side during Short Circuit test on the transformer.
A
LV
B
HV
C
both side (one by one)
D
None of these

Question

Normally Supply voltage is applied on ___________ side during Short Circuit test on the transformer.

Examoogle · Accepted Answer

HV

Explanation: In the Short Circuit (SC) test, the low-voltage (LV) winding is short-circuited, and a reduced voltage is applied to the high-voltage (HV) winding to circulate the full-load rated current. Applying voltage to the HV side is preferred because it requires a more manageable, lower value of current for the same power rating of the supply equipment.

Working Principle: The SC test is conducted to determine the full-load copper losses and equivalent impedance parameters ($R_{eq}$, $X_{eq}$) of the transformer. By shorting the LV side, the core flux becomes very small (since $V_{applied} \approx 0.05$ to $0.1$ of rated voltage), meaning core losses are negligible and the total power measured by the wattmeter represents almost entirely copper losses.

Key Formulas: $P_{sc} = I_{rated}^2 \cdot R_{eq}$ — Copper loss calculated from SC test; $Z_{eq} = \frac{V_{sc}}{I_{sc}}$ — Equivalent impedance referred to HV side

Key Points: LV winding is always short-circuited to avoid extremely high currents during testing.; The applied voltage is typically 5-10% of the rated voltage.; Wattmeter reading at SC test is treated as Full Load Copper Loss.; Core losses are neglected due to low flux density at reduced applied voltage.

Advantages: Requires low power source capacity.; Accurately measures transformer leakage impedance.

Disadvantages: Does not determine core losses.; Requires precise measurement of low voltage levels.

Applications: Calculation of efficiency at any load.; Determining voltage regulation of the transformer.

Additional Info: The test is performed on the HV side because the rated current $I_{HV} = \frac{S}{V_{HV}}$ is smaller than $I_{LV}$, making it easier to control with standard laboratory equipment.. If the test were performed on the LV side, the supply source would need to provide a very high current at a very low voltage, which is practically difficult.

Answer: B is correct — The HV side is used for applying voltage during a short-circuit test to allow for lower current handling and higher measurement accuracy.

Exam Tip: Always remember: SC test measures Copper loss (variable loss) and OC test measures Iron loss (constant loss).

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