Which parameter does the short-circuit test determine?

• A. It measures open-circuit voltage.
• B. It determines the generator’s synchronous reactance (Xs) and resistance (R) under short-circuit conditions.
• C. It measures phase angle during standstill.
• D. It determines maximum cooling capacity.

Answer: (B)

When you run a short-circuit test on a generator, you lock the rotor (standstill) and apply a reduced stator voltage until the full-load current flows. The goal is to measure the impedance the machine presents under a short circuit. You compute Zs as the applied voltage divided by the short-circuit current (Zs = Vsc / Is). That impedance is made up of winding resistance and synchronous reactance, so from Zs you can determine the resistance (R) and the synchronous reactance (Xs) under short-circuit conditions. This information is essential for predicting short-circuit current and voltage regulation in the system. The others aren’t what this test provides: open-circuit voltage comes from a no-load test, phase angle during standstill isn’t the primary parameter obtained here, and maximum cooling capacity is a thermal property, not an electrical one.