What does the short-circuit test reveal about a generator?

• A. The open-circuit emf and saturation.
• B. The generator’s synchronous reactance (Xs) and resistance (R) under short-circuit conditions.
• C. The temperature rise of windings.
• D. The short-circuit current and stator winding resistance.

Answer: (B)

When you short the generator’s terminals and apply a test voltage, the current that flows is determined by the machine’s internal impedance. That impedance is the combination of resistance and synchronous reactance, so the short-circuit test is used to determine R and Xs (the components of the synchronous impedance) under short-circuit conditions. By measuring the applied voltage and the resulting short-circuit current, you can compute Zs = V / I, and from its real and imaginary parts separate R and Xs. This is different from an open-circuit test, which reveals the generated emf and saturation effects, and it’s not a direct measure of winding temperature. The short-circuit test specifically provides the generator’s internal resistance and synchronous reactance that govern how it behaves during faults and heavy loading.