The motors that have the starting capacitor are very similar to the split phase motors. It can be said that among the main differences, the inclusion of a series electrolytic capacitor should be highlighted, in the same way as the starting auxiliary winding. In the range of speeds occurring, the main winding alone can develop practically the same torque as the combined windings. In the case of high speeds, which may vary from about 80% to 90% of the synchronous speed, the curve find more here of the conjugate with the combined windings will cross the conjugate curve of the main winding so that, for speeds above this point, the motor it can develop smaller torque, for any slip, with the auxiliary circuit connected than without it.
The capacitor allows a greater angle of lag between the main and auxiliary winding currents, thus allowing high starting torque. As in the split-phase motor, the auxiliary circuit is disconnected when the motor reaches, on average, between 75% and 80% of the synchronous speed. Due to the fact that the curves do not always intersect at the same point and the centrifugal circuit breaker does not open at the same speed, it is common to make the opening take place just before the curves intersect.