What happens to the rotor of a single-phase motor when voltage is applied to the stator windings?

What happens to the rotor of a single-phase motor when voltage is applied to the stator windings?

• A. It immediately rotates
• B. It remains stationary
• C. It moves up and down like a piston
• D. It begins to rotate after a brief delay

Answer: (A)

When voltage is applied to the stator windings of a single-phase motor, the correct process is for the rotor to begin to rotate after a brief delay. This phenomenon occurs because the alternating current creates a magnetic field in the stator that induces the rotor to start rotating. However, due to the nature of single-phase motors, particularly split-phase and capacitor types, the rotor does not experience a continuous starting torque that would cause it to rotate immediately upon voltage application. Instead, it needs some time to overcome inertia and start its motion after the magnetic field is established. This delay happens because the magnetic field produced by a single-phase supply is not rotating, but rather stationary. As a result, the rotor does not see a rotating magnetic field initially, which is necessary for it to start turning. Instead, the rotor will remain stationary until the motor reaches a threshold speed or the additional starting circuitry (if applicable) helps to establish the necessary torque for movement. In summary, while a single-phase motor's rotor may eventually begin to rotate, it does so only after a brief delay, not immediately. Understanding this delay is key when working with single-phase motor technologies and their operational characteristics.

When voltage is applied to the stator windings of a single-phase motor, the correct process is for the rotor to begin to rotate after a brief delay. This phenomenon occurs because the alternating current creates a magnetic field in the stator that induces the rotor to start rotating. However, due to the nature of single-phase motors, particularly split-phase and capacitor types, the rotor does not experience a continuous starting torque that would cause it to rotate immediately upon voltage application. Instead, it needs some time to overcome inertia and start its motion after the magnetic field is established.

This delay happens because the magnetic field produced by a single-phase supply is not rotating, but rather stationary. As a result, the rotor does not see a rotating magnetic field initially, which is necessary for it to start turning. Instead, the rotor will remain stationary until the motor reaches a threshold speed or the additional starting circuitry (if applicable) helps to establish the necessary torque for movement.

In summary, while a single-phase motor's rotor may eventually begin to rotate, it does so only after a brief delay, not immediately. Understanding this delay is key when working with single-phase motor technologies and their operational characteristics.