SOLUTION

• In order to self-start a single-phase induction motor one must create a rotating magnetic field on the stator. Therefore split phase motor has two winding one is starting winding and the other is main winding or running winding.
• The starting winding has fewer turns and a small diameter, therefore, it has high resistance and low inductance.
• The running winding has a heavier wire of more turns, therefore, it has low resistance and high inductance.
• As we know that for high inductance current lags behind voltage by a large angle and for high resistance, the current is almost in phase with the voltage.
• Therefore for starting winding the current lags behind the supply voltage by an angle of 15 degrees while for running winding the current lags behind voltage about an angle of 40 degrees.
• This difference in phase angle creates a phase delay in the rotating magnetic field that allows the motor to start otherwise without the phase difference the motor will oscillate in the standstill position.