Electrical Engineering XYZ MCQ
The leakage reactance of a 3-phase alternator is determined by performing:
- Open circuit and short circuit tests
- Short circuit and slip tests
- Open circuit and zero power factor tests
- Zero power factor and slip tests
Correct answer: 3. Open circuit and zero power factor tests
Explanation: The leakage reactance of a 3-phase alternator can indeed be determined by performing both open circuit and zero power factor tests. These tests are used to assess different aspects of the alternator’s performance.
- Open Circuit Test: This test is conducted with the alternator running at rated speed with all its terminals open-circuited. It helps determine the open-circuit voltage (no-load voltage) and provides information about the magnetizing reactance and the core loss.
- Zero Power Factor Test: In this test, the alternator is loaded to the rated current at zero power factor (lagging). The purpose is to determine the voltage drop and the synchronous impedance of the machine under loaded conditions. The synchronous impedance includes both the synchronous reactance and the leakage reactance.
By analyzing the data obtained from these tests, one can calculate and separate the components of the synchronous impedance, which includes the leakage reactance. Therefore, open circuit and zero power factor tests together contribute to the determination of the leakage reactance of a 3-phase alternator.