A: As the single-phase motor contains the starting capacitor, the start-up capacitor is designed to generate a 90-degree phase difference between the primary and secondary windings of the single-phase motor, resulting in a rotating magnetic field to rotate the motor. The size of the starting capacitor is generally designed according to the frequency 50Hz, but when the single-phase motor frequency control, the frequency will not always work at 50Hz, it is difficult to produce rotating magnetic field, the common method is to remove the single-phase motor start and run Capacitor, the use of two-phase control method.

After adopt the method of removing the capacitor, the software algorithm improvements, it is necessary to ensure that limit the starting current, but also to ensure that the starting torque, so the final output voltage than the direct start voltage amplitude is low, resulting in load capacity decreased.