These are of different types based on their way of starting since these are of not self starting. Those are split phase, shaded pole and capacitor motors. When the supply voltage is applied, current in the main winding lags the supply voltage because of the main winding impedance. The angel between the two windings is sufficient phase difference to provide a rotating magnitude field to produce a starting torque.
Applications of Single Phase Induction Motor These are used in low power applications and widely used in domestic applications as well as industrial. We arrange the three-phase winding in such a manner in the slots that they produce one rotating magnetic field when we switch on the three-phase AC supply source. The stator of the motor consists of overlapping winding offset by an electrical angle of o. When we connect the primary winding, or the stator to a 3 phase AC source, it establishes rotating magnetic field which rotates at the synchronous speed.
Slip, which varies from zero at synchronous speed and 1 when the rotor is at rest, determines the motor's torque. Since the short-circuited rotor windings have small resistance, even a small slip induces a large current in the rotor and produces significant torque. These speed variations can cause load-sharing problems when differently sized motors are mechanically connected. Various methods are available to reduce slip, VFDs often offering the best solution The rotor of three phase induction motor consists of a cylindrical laminated core with parallel slots that can carry conductors.
The conductors are heavy copper or aluminium bars fitted in each slot and short-circuited by the end rings. The slots are not exactly made parallel to the axis of the shaft but are slotted a little skewed because this arrangement reduces magnetic humming noise and can avoid stalling of the motor. As the rotor winding in an induction motor are either closed through an external resistance or directly shorted by end ring, and cut the stator rotating magnetic field, an Emf is induced in the rotor copper bar and due to this Emf a current flows through the rotor conductor.
The working principle of three phase induction motor, it may be observed that the rotor speed should not reach the synchronous speed produced by the stator. If the speeds become equal, there would be no such relative speed, so no Emf induced in the rotor, and no current would be flowing, and therefore no torque would be generated.
Consequently, the rotor cannot reach the synchronous speed. The difference between the stator synchronous speed and rotor speeds is called the slip. The rotation of the magnetic field in an induction motor has the advantage that no electrical connections need to be made to the rotor. Advantages of Induction Motor 1. The most important advantage of an induction motor is that its construction is quite simple in nature.
The working of the motor is independent of the environmental condition. This is because the induction motor is Robust and mechanically strong. A Squirrel cage induction motor does not contain Brushes, Slip rings and Commutators. Due to this reason, the cost of the motor is quite low. The stator carries a 3-phase winding called as stator winding while the rotor carries a short circuited winding called as rotor winding. The stator winding is fed from 3-phase supply and the rotor winding derives its voltage and power from the stator winding through electromagnetic induction.
Therefore, the working principle of a 3-phase induction motor is fundamentally based on electromagnetic induction. Consider a portion of a three phase induction motor see the figure. When the stator winding is connected to a balanced three phase supply, a rotating magnetic field RMF is setup which rotates around the stator at synchronous speed N s.
The RMF passes through air gap and cuts the rotor conductors, which are stationary at start. Since the rotor circuit is short-circuited, a current starts flowing in the rotor conductors. Now, the current carrying rotor conductors are in a magnetic field created by the stator.
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