Single phase induction motor is not self starting motor. Starting winding use for self start in single phase induction motor. Torque ∝ sin - phase angle difference between main winding and starting winding. In split phase induction motor starting winding is highly resistive. So current flowing in starting winding lag behind the applied voltage very small and main winding is highly inductive.
So phase difference between the main and starting winding is approx 30°. T ∝ sin 30 In capacitor start induction motor starting winding connected with capacitor so current flowing in starting winding lead behind applied voltage and main winding is highly inductive.
So phase difference between the main and starting winding is approx 30° T ∝ sin 30 So height starting torque in capacitor start induction motor.