Question

Short circuit MVA of a 3-phase alternator is ______

• A. Directly proportional to \( Z_{pu} \)
• B. Inversely proportional to square of \( Z_{pu} \)
• C. Inversely proportional to \( Z_{pu} \)
• D. Directly proportional to square of \( Z_{pu} \)

Hint:

Lower per-unit impedance \( Z_{pu} \) means higher fault MVA – important for circuit breaker selection.

Answer 1

The Correct Option is C

The short circuit MVA is given by: \[ \text{Short Circuit MVA} = \frac{\text{Rated MVA}}{Z_{pu}} \] So, it is inversely proportional to the per-unit impedance \( Z_{pu} \) of the alternator.