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 the salient pole, and there are two poles and four poles. Each magnetic pole has a small slot at the 1/3-1/4 full pole face, and the magnetic pole is divided into two parts, and a short-circuit copper ring is fitted on the small part as if this part of the magnetic pole is covered, so It is called a shaded pole motor.
The single-phase winding is sheathed on the entire magnetic pole, and the coil of each pole is connected in series(single-phase voltage stabilizer for home), and the polarities generated during the connection must be arranged in order of N, S, N, 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-circuited 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.
To make the single-phase motor 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 so that the current with the main winding The phase difference is approximately 90 degrees, 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 starting winding is disconnected by means of a centrifugal switch or other automatic control device installed on the rotor. During normal operation, only the main winding is available. jobs.
Therefore, the start 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 capacitive single-phase motor. To change the direction of this motor, it can be achieved by changing the position of the capacitor in series.