Difference between 1 phase & 3 phase motors: Phase shifting for obtaining torque in case of single phase motors is obtained by connecting capacitor in one winding. Other winding is connected to supply directly. In case of 3 phase motors, torque is automatically obtained by three sets of windings placed and connected 120 degree apart from each other. These motors are normally available from 2 poles to 10 poles. Speed is calculated by formula: N = 120 x frequency / no. Of poles.