How does induction happen at the single phase induction motor rotor?
Due to rotating magnetic field.
Due to rotating rotor.
Due to ac current provided to stator windings.
Due to dc current provided to rotor windings.
The correct answer and explanation is:
The correct answer is: Due to the rotating magnetic field.
In a single-phase induction motor, induction occurs due to the interaction between the rotating magnetic field generated by the stator and the rotor. Here’s how it works in more detail:
- Rotating Magnetic Field: When alternating current (AC) flows through the stator windings of the motor, it creates a magnetic field that changes direction continuously. This changing magnetic field rotates around the stator at a certain speed known as the synchronous speed. This rotating magnetic field is essential for the motor to work.
- Induced Current in Rotor: The rotor of the single-phase induction motor is typically made of laminated iron, and it is placed within the rotating magnetic field produced by the stator. According to Faraday’s Law of Induction, a changing magnetic flux (in this case, the rotating magnetic field) induces a current in the rotor. Since the rotor is not connected to any external power source (in the case of squirrel-cage rotors), the current induced in the rotor is due to the interaction with the rotating magnetic field.
- Interaction and Torque Production: The induced current in the rotor produces its own magnetic field, which interacts with the rotating magnetic field of the stator. This interaction results in a force that generates torque, causing the rotor to start rotating. The rotor will try to follow the stator’s magnetic field, but it will always lag behind due to the difference in speed between the rotating magnetic field and the rotor’s actual speed. This difference in speed is known as “slip,” and it is essential for the motor’s operation.
- Why Not Other Options?
- Rotating Rotor: The rotor does not initially rotate; it begins rotating only when the induced current interacts with the rotating magnetic field.
- AC Current to Stator Windings: While the AC current in the stator creates the rotating magnetic field, the induction in the rotor specifically occurs due to this rotating field.
- DC Current in Rotor: Single-phase induction motors do not use DC current in the rotor. DC current would not create a rotating magnetic field, and thus no induction would occur.
In summary, the induction in a single-phase induction motor’s rotor is caused by the rotating magnetic field created by the stator windings, which induces a current in the rotor and generates the necessary torque for rotation.