split phase induction motor

SPLIT PHASE INDUCTION MOTOR

 

In this type there will be two windings.
  • main winding
  • auxiliary winding or starting winding
The circuit diagram is show in below fig which consist of main winding and auxiliary winding, where the starting winding has more resistive in nature and the main winding has more inductive in nature.



 This is because to start this motor the currents of main winding(Im) and starting winding (Is) should maintain a phase angle less than 90o and both windings produces Φm and Φs fluxes .By this rotating magnetic field is produced and induction motor will starts rotating in one direction.The direction of rotor can be changed by changing the terminal of main winding or starting winding.This makes change in the direction of rotating magnetic field and rotor rotates in opposite direction.
Due to high inductive nature of main winding its current Im lags voltage V by an angle less than 90o and highly resistive nature of starting winding ,the current in it Is will be in phase with voltage V, but practically it is not in phase with V.



The auxiliary winding is disconnected from circuit when the speed of rotor reaches 75 to 80% of synchronous speed by the help of centrifugal switch.At 75 to 80% of synchronous speed the slip is minimum, so the rotor won't stop rotating at that time and it catches the RMF(rotating magnetic field).But the main reason for removing or disconnecting of auxiliary winding is that after 75 to 80 % of synchronous speed the starting winding starts producing heat because it is highly resistive so, this make damage to auxiliary winding and it cannot be used for future purpose.

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