Notes on Short Circuit Test

Summary of Previous Lecture

• The previous lecture discussed the no-load test.
• Importance of rated voltage and rated frequency.
• Impact of frequency reduction and its effect on magnetizing current.

Introduction to Short Circuit Test

• Importance of short circuit test.
• This test has two sides: LV (Low Voltage) and HV (High Voltage).
• The test can be conducted on either side, but it is preferable to do it on the HV side.

Test Procedure

• The short circuit test is primarily conducted on HV.
• Voltmeter, ammeter, and wattmeter are used.
• Voltage is high and current is low on the HV side, while voltage is low and current is high on the LV side.

Equations under Short Circuit Condition

• Calculation of voltage and current readings.
• Total impedance in the short circuit is denoted by Z equivalent.
• Power factor calculation: WSC = VSC * ISC * cos(phi SC).

Power Factor and Impedance Triangle

• Importance of Z equivalent, R equivalent, and X equivalent.
• Explanation of the impedance triangle.
• Calculation of power factor angle (theta z).

Impact of Frequency

• Frequency changes have no effect on R equivalent.
• However, there will be a change in X equivalent.
• Power factor will improve with stable voltage.

Current Under Short Circuit Condition

• Calculation of ISC: ISC = VSC / Z equivalent.
• Difference between rated current and steady-state current.
• Per unit value of rated current will always be 1.

Conclusion

• It is necessary to understand the procedure of the short circuit test and its importance.
• The next lecture will discuss the efficiency of transformers.

Note: These notes will be helpful in understanding the short circuit test and its significance.