A single-phase induction motor operates on the principle of electromagnetic induction to produce rotational motion. When AC voltage is applied to the motor’s stator windings, it creates a rotating magnetic field. In a single-phase motor, this rotating magnetic field is not inherently present due to the single-phase supply, so auxiliary mechanisms are used to create it. Typically, this is achieved through the use of auxiliary windings or starting methods such as capacitors.
The operation of an induction motor can be explained step by step as follows: when AC voltage is applied to the stator windings, it creates a magnetic field that alternates in direction according to the frequency of the applied voltage. This alternating magnetic field induces a current in the rotor bars due to Faraday’s Law of electromagnetic induction. The interaction between the rotating magnetic field and the induced current in the rotor bars generates a torque, causing the rotor to turn.
In a single-phase induction motor, achieving self-starting capability is essential. This is typically accomplished by providing an auxiliary winding and a starting capacitor. The auxiliary winding is placed at an angle to the main winding, creating a phase difference that produces a rotating magnetic field during starting. The starting capacitor is used to shift the phase of the auxiliary winding current, enabling the motor to develop sufficient torque to overcome inertia and start rotating. Once the motor reaches near-synchronous speed, the starting capacitor is usually disconnected from the circuit by a centrifugal switch or other means.
The basic principle behind the operation of an induction motor involves the interaction between the rotating magnetic field produced by the stator windings and the induced current in the rotor. When AC voltage is applied to the stator windings, it creates a rotating magnetic field that induces currents in the rotor conductors. These currents in the rotor interact with the rotating magnetic field, producing a torque that causes the rotor to rotate. The motor continues to run at a speed slightly less than the synchronous speed of the rotating magnetic field, known as slip, which is necessary for the motor to develop torque and perform useful work.