Electrical Engineering XYZ MCQ
A DC series motor is accidentally connected to single phase ac supply voltage. The torque produced will be:
- Steady and unidirectional
- Pulsating and unidirectional
- Oscillating
- None of above
Correct answer: 3. Pulsating and unidirectional
Explanation: The correct answer is “Pulsating and unidirectional.”
When a DC series motor is accidentally connected to a single-phase AC supply voltage, the torque produced will be pulsating and unidirectional. This is because a DC series motor is designed to operate on direct current (DC), and when connected to single-phase AC, the current flowing through the motor windings will be alternating.
The nature of the torque produced in this situation is pulsating because the direction of the current changes with each half-cycle of the AC waveform. However, the torque will predominantly be in one direction, resulting in unidirectional motion. This is due to the inherent design of the DC series motor, where the field winding and armature winding are connected in series, causing the torque to have a pulsating but predominantly unidirectional characteristic.
So, the correct option is “Pulsating and unidirectional.”