Why is a three phase induction motor self starting?

Answer 1

A brushless DC motor is self-starting using only one magneto-sensitive element because the motor is of a two-phase type and is provided with a detection device which detects towards which of the two phases the rotor is mainly directed. A presetting circuit compares the detected rotor position with the state of an energizing circuit in order to set this circuit so that the energizing circuit energizes the stator phases for said specific rotor position in such a way that starting of the motor is guaranteed, although initially with an undefined direction of rotation. By presetting the commutating direction of the energizing circuit the rotor subsequently locks onto the field and rotates in the correct direction if it has started in the incorrect direction

Answer 2

first the induction motor is not a self starting because when induction motor compare to other motor the for one cycle it reaches 120 degree out of 180 degree so it is not star we need add external ressitive load so this is called self starting

Answer 3

The continually expanding and contracting magnetic fields set up in each of the three windings, which are 120 degrees apart, combine, to form a resultant field that rotates within the stator, sweeping around the air gap. This induces voltages into the rotor bars, and the magnetic fields set up by the resulting rotor currents combine with the rotating stator field, dragging the rotor around with them.

Answer 4

By adding an additional starting winding with a resistance in series at an angle of 90 degree from running winding we can made the motor self starter