Dingfeng Capacitor -- Single-phase motor starting capacitor

Oct 12,2019

Some household appliances used in our daily life, such as air conditioners, refrigerators, washing machines, electric fans, etc., are widely used in single-phase asynchronous motors, which use start-up capacitors.

For single-phase motors, there is one running winding (main winding) and one starting winding (secondary winding). Running the winding is the working winding of the motor, also called the main winding. The main task is to ensure the normal operation of the motor. The start winding is also called the secondary winding, which mainly provides a different phase (90 degrees) current from the main winding at start-up, generating a rotating magnetic field for the motor to start smoothly.


Single-phase electricity does not produce a rotating magnetic field and requires another set of start windings to match. Since there is only a single phase 220 VAC, a capacitor is connected in series with the start winding. The characteristic of the capacitor is that the voltage cannot be abrupt, so the current of the starting coil is advanced by 90° from the running coil. This creates a rotating magnetic field in the stator space, and the rotor cuts the magnetic lines of force to generate an induced current to form an induced magnetic field. The two magnetic fields of the stator and the rotor interact. The magnetic field induced by the rotor interacts with the magnetic field of the stator, causing the rotor to follow the magnetic field of the stator. The direction of the rotor of the motor coincides with the direction of the rotating magnetic field. In this way, the rotor can be rotated continuously, allowing the motor to start normally.

Some single-phase motors are one capacitor, and some are two capacitors. Only one capacitor is called the starting capacitor. There are two capacitors, one is the starting capacitor, the other is the running capacitor, and generally the capacity of the starting capacitor is greater than the capacity of the running capacitor.



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