Starting Capacitor Motor

As in the split-phase electric motor the auxiliary circuit is disconnected when the motor reaches between 75% and 80% of the synchronous speed. In this range of speeds, the main winding alone develops almost the same torque as the combining windings. For higher velocities, between 80% and 90% of the synchronous speed, the curve of the conjugate with the combined windings crosses the curve of the conjugate of the main winding so that, for speeds above this target, the motor develops smaller torque 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 the same speed, it is very common to make the aperture occur on the average, just before the curves intersect. After disconnection of the auxiliary circuit, its operation is the same as that of the split-phase motor. With its high starting torque between 200% and 350% of the rated torque, the starter capacitor motor can be used in a wide range of applications and is manufactured in capacities ranging from 1/4 hp to 1,5 hp.