For application of split winding, it is necessary for the electric motor to have two circuits in parallel per phase. Two steps are used to connect the motor to the mains, where a contactor connects part of the winding to the mains (usually half the winding) for a short time, approximately 4 seconds and another contactor connects the remainder of the winding to the mains, completing the call. This method can be used when the engine starts at a vacuum, and only after reaching the nominal speed does the other part of the winding connect, and then the load is applied and the load gradually increases with the rotation. Example: Fans, centrifugal pumps, etc.
The curves represent the conjugate x velocity of the split winding start method. The starting conjugate developed by the split winding method is admirably smaller than the direct starting conjugate, and is even smaller than the full charge conjugate. This should be an advantage when you want a soft match. In this method, the motor will accelerate the load until it is close to the rated speed, ie the load resistant torque must always be lower than the torque developed with the split winding. https://www.mrosupply.com/brands/reelcraft/