Electrical Engineering XYZ MCQs
As compared to DOL starting, a cage induction motor with star-delta starting shall have:
- More starting time
- Smoother acceleration
- Reduced starting current
- More starting torque
Correct answer: 3. Reduced starting current
Explanation: Star-delta starting method reduces the starting current by connecting the motor windings in star configuration during the start phase, which effectively applies only 1/√3 (about 58%) of the line voltage to each winding. This results in a substantial reduction in the starting current compared to Direct-On-Line (DOL) starting, where the full line voltage is applied, resulting in higher starting currents. Star-delta starting does not inherently affect the starting time, provide smoother acceleration, nor increase the starting torque; it specifically aims to mitigate the initial current draw.