Single-phase motors generally refer to low-power single-phase asynchronous motors powered by single-phase AC power (AC220V). Single-phase asynchronous motors usually have two-phase windings on the stator, and the rotor is of ordinary squirrel cage type. The distribution of the two-phase windings on the stator and the different power supply conditions can produce different starting and operating characteristics. When a single-phase sinusoidal current passes through the stator windings, the motor will generate an alternating magnetic field. The strength and direction of this magnetic field change sinusoidally with time, but it is fixed in space, so this magnetic field is also called alternating Pulsating magnetic field. This alternating pulsating magnetic field can be decomposed into two rotating magnetic fields with the same speed and opposite rotation directions. When the rotor is stationary, these two rotating magnetic fields produce two equal and opposite torques in the rotor, making the synthesis The torque is zero, so the motor cannot rotate. When we use external force to rotate the motor in a certain direction (such as clockwise rotation), then the cutting magnetic field lines between the rotor and the clockwise rotating magnetic field become smaller; the rotor and the counterclockwise rotating magnetic field The movement of the cutting magnetic field lines becomes larger. In this way, the balance is broken, the total electromagnetic torque produced by the rotor will no longer be zero, and the rotor will rotate in the direction of pushing. To make the single-phase motor of the national standard rotate automatically, we can add a starter winding to the stator. The starter winding and the main winding are separated by 90 degrees in space. The starter winding should be connected in series with a suitable capacitor to make the The currents of the windings are approximately 90 degrees apart in phase, which is the so-called principle of phase separation. In this way, two currents that are 90 degrees apart in time pass through two windings that are 90 degrees apart in space, and a (two-phase) rotating magnetic field will be generated in space. Under the action of this rotating magnetic field, the rotor can start automatically. After starting, when the speed rises to a certain level, the start winding is disconnected by means of a centrifugal switch or other automatic control device installed on the rotor, and only the main winding works during normal operation. Therefore, the starter winding can be made into a short-time working mode. But there are many times, the starting winding is not disconnected. We call this kind of motor a single-phase motor. To change the direction of this kind of motor, just change the terminal of the auxiliary winding. In a single-phase motor, another method of generating a rotating magnetic field is called the shaded pole method, also known as a single-phase shaded pole motor. The stator of this kind of motor is made of salient pole, and it has two poles and four poles. Each magnetic pole has a small slot at the 1/3-1/4 full pole face, dividing the magnetic pole into two parts, and putting a short-circuit copper ring on the small part, as if covering this part of the magnetic pole. So it is called a shaded pole motor. The single-phase winding is sleeved on the entire magnetic pole, and the coil of each pole is connected in series, and the polarities generated during the connection must be arranged in order of N, S, N, and S. When the stator winding is energized, the main magnetic flux is generated in the magnetic poles. According to Lenz's law, the main magnetic flux passing through the short-circuit copper ring generates an induced current in the copper ring with a phase delay of 90 degrees. The magnetic flux generated by this current The flux also lags behind the main magnetic flux in phase, and its function is equivalent to the start winding of a capacitor motor, which generates a rotating magnetic field to make the motor rotate.