Motor run capacitors: AC electrolytic capacitor or polypropylene, polyester capacitor used to start a single phase asynchronous motor. Single-phase motor through single-phase current cannot produce a rotating magnetic field,it need to take the motor run capacitors is used to phase, the purpose of which is to make two winding current produced nearly 90 Eve joy, phase difference, to produce a rotating magnetic field.
The capacitor induction motor has two windings, the motor run capacitors and running winding. Two windings differ by 90 degrees in space. At the start of the winding of the series has a large capacity capacitor. When the motor run capacitors running and start winding through the single-phase alternating current, due to the capacitor to start winding current in time than the running winding current advance angle of 90 degrees and arrived first at maximum. In time and space to form two same pulse magnetic field, so that a rotating magnetic field is generated in the air gap between the stator and rotor, under the effect of rotating magnetic field and rotor generate induced current, current and rotating magnetic field resulting from the interaction of electromagnetic torque, make electric machine rotate.
To make the single-phase motor can automatically rotate together.The motor run capacitors are connected in series with a suitable capacitor, with the main winding current the in phase difference of 90 degree of approximation, that is, the so-called separation theory. So the two time difference of 90 degrees of the current through the two in the space difference of 90 degrees of winding, will produce in space (two-phase) rotating magnetic field. Under the action of the rotating magnetic field, the rotor will start automatically, after the start, until the speed is raised, with a mounted on the rotor of the centrifugal switch or other automatic control device in the starting winding is disconnected,when it works normally it only has the main winding. As a result, the starting winding can be made in a short time. But there are a lot of time, the starting winding and constantly open, we call this kind of motor for a single phase motor, to change the steering of the motor can be achieved by changing the position of the capacitor.