2. There are two windings in the fan, a main winding and an auxiliary winding. The main winding plays the role of running, and the auxiliary winding plays the role of starting. The capacitor changes the size of the magnetic field so that the phase difference between the main winding and the auxiliary winding is 180 degrees. If the main winding leads the auxiliary winding by 180 degrees, the motor rotates forward; Otherwise, the main winding lags behind the auxiliary winding 180 degrees, and the motor reverses;
You can also find a double control switch. Terminals at both ends are respectively connected to one end of the main winding and one end of the auxiliary winding, and the center contact of the double-control switch is connected to the live wire of the power supply. Then the two terminals at the other end of the main winding and the auxiliary winding are connected together and connected to the zero line of the power supply. Press the double control switch, the fan motor rotates forward, and press the double control switch, the fan motor rotates backward; The starting capacitor is reversed, and the current of the main winding of the motor is 90 degrees later than that of the auxiliary winding, so the motor commutates.