Starting Capacitor Motor

The electric motor with capacitor of starting is a motor similar to the one of split phase, having as difference the inclusion of a capacitor electrolytic in series with the auxiliary winding of start. The capacitor admits a larger angle of lag between the main and auxiliary winding currents, thus providing high starting torques. As in the split-phase motor, the auxiliary circuit will be switched off when the motor reaches 75% to 80% of the synchronous speed. In this range of speeds, the winding alone develops almost the same torque as the combined windings.

skf bearing 23024

For higher velocities between 80% and 90% of the synchronous speed, the torque curve with the combined windings crosses the torque curve of the main winding so that at speeds above this point the motor will develop less torque and for any slip, with the auxiliary circuit connected than without it. Because the curves do not always intersect at the same point, and the centrifugal breaker does not always open at exactly the same speed, it is a common technique to make the aperture occur, on average, just before the curves intersect.