Simply put, the capacitor is used to generate a phase difference, and the magnetic field of the motor is "asynchronous", and the motor rotates.
The single-phase asynchronous motor consists of the main winding (also known as the running winding) and the secondary winding (also known as the starting winding), and the two windings are separated by an electrical angle of 90° in space. After the capacitor is phase-separated, the two windings are fed with alternating currents with different phases, and a rotating magnetomotive force will be generated in the motor.
If only the main winding is connected to single-phase alternating current, the pulsating magnetomotive force generated in the motor can be decomposed into two rotating magnetomotive forces of equal size, the same speed and opposite directions. The two magnetomotive force magnetic fields with opposite directions act together on the rotor, and the electromagnetic torque generated at rest is equal in magnitude and opposite in direction, so it cannot be started.
If the number of turns of the main winding and the secondary winding are equal, the space difference is 90° electrical angle, and an alternating current with a phase difference of 90° is introduced, then a circular rotating magnetic field will be generated in the motor, and the motor rotor will rotate with it under its action.
If the two windings are asymmetrical, and the phase difference of the current flowing into them is not equal to 90°, the elliptical rotating magnetic field generated in the motor is decomposed into a larger and a smaller circular rotating magnetic field, and their rotational speeds are equal in opposite directions. , the motor rotates in the direction of rotation of the magnetic field of the larger magnetomotive force. Changing the head and tail ends of the secondary winding (or the head and tail ends of the main winding) can change the direction of the elliptical rotating magnetic field, and the motor can also be reversed. But a head-to-tail motor that changes both windings at the same time does not change the steering.
A single-phase motor must have two sets of windings with a space of 90° electrical angle, and the alternating current with a certain phase difference will generate a rotating magnetic field, and the motor will start by itself and rotate along the direction of the rotating magnetic field.
Strictly speaking, the motor cannot be distinguished by the voltage level. The so-called 220V and 380V are just our daily abbreviations. Here we should say single-phase and three-phase.
The rotation of an AC motor relies on a rotating magnetic field created by an electric current. The three-phase motor flows through three-phase currents with a phase difference of 120 degrees, which can generate a rotating magnetic field. The single-phase current flowing through the single-phase motor cannot generate a rotating magnetic field, and a certain method needs to be taken to make it generate a rotating magnetic field. One of the methods is to use a capacitor, and it is also the most common method. The capacitor is used for phase separation, the purpose is to make the two The currents in the Rao group produce a phase difference of approximately 90° to generate a rotating magnetic field. In three-phase electricity, there is a phase difference between the currents between each two phases, and there is no need for phase separation.
Capacitive induction motors have two windings, the start winding and the run winding. The two windings are 90 degrees apart in space. A capacitor with a large capacity is connected in series on the starting winding. When the running winding and the starting winding pass through a single AC current, the current in the starting winding is 90 degrees ahead of the current in the running winding due to the action of the capacitor, and reaches the maximum first. value. Two identical pulsed magnetic fields are formed in time and space, so that a rotating magnetic field is generated in the air gap between the stator and the rotor. Under the action of the rotating magnetic field, an induced current is generated in the rotor of the motor, and the interaction between the current and the rotating magnetic field produces The electromagnetic field torque makes the motor spin.
