Capacitor-started single-phase motor non-frequent commutation circuit

The resistance values ​​of the main winding LR and the secondary winding LA of this kind of motor are not equal. If measured with a multimeter, the winding with a smaller resistance value and not in series with the capacitor C is the main winding LR, which has a larger resistance value and is connected in series with the capacitor C. is the secondary winding LA. The working principle is shown in the figure. In the figure, C is the starting capacitor of the secondary winding, usually 1μF, and SA is the double-pole double-throw toggle switch KN3-3-2×2. When the motor is used as an exhaust fan, throw the SA to the "positive" position, the motor will rotate forward, and the exhaust fan will exhaust air to the outdoors; when the SA is thrown to the "reverse" position, it will rotate in the reverse direction, and the exhaust fan will send air to the room. Since the toggle switch SA only has two-way double throw and no neutral (stop), an additional power switch S is installed in the circuit.