Induction Motor Rotor Dynamics Explained
In a 3-phase induction motor, the stator winding produces a rotating magnetic field. This field rotates at synchronous speed and sweeps across the rotor conductors.
Electromagnetic Induction in the Rotor
According to the principles of electromagnetic induction, whenever a conductor cuts magnetic flux, a voltage is induced across it. In the induction motor:
- The relative motion between the rotating magnetic field and the stationary (or rotating slower than the field) rotor conductors causes voltage induction.
- This induced voltage drives currents within the rotor conductors, assuming the rotor circuit is closed.
- These circulating currents within the rotor are specifically termed eddy currents.
The interaction between the stator's rotating magnetic field and the magnetic field produced by these eddy currents in the rotor generates the torque that makes the motor rotate.
Therefore, the direct phenomenon developed in the 3-phase induction motor rotor due to the rotating magnetic field is eddy currents.
Important Questions from Three Phase Induction Motor
For a slip 's' and supply frequency 'f', the frequency of current in rotor will be-
The rotating magnetic field in a three-phase, 6-poles, 50 Hz slip ring induction motor will rotate at-
The synchronous speed of a three phase induction motor having 20 poles and connected to a 50 Hz source is-
The rotor current frequency in a slip-ring induction motor depends on-
The power factor of an induction motor operating at no load is around:
