"220V AC Cooling Fan" is divided into two categories, both DC and AC. DC cooling fan is to provide a DC power supply: DC motor has two major components of the stator and rotor, stator pole there, "220V AC Cooling Fan" rotor windings, the power, but also the formation of a magnetic field on the rotor, stator and rotor there is an angle between the magnetic poles, the magnetic field in the stator and rotor mutual attraction under the motor rotation. Change the position of the brush, you can change the direction of the angle between the stator and rotor poles, thereby changing the direction of rotation of the motor. Such a balance is broken, "220V AC Cooling Fan" total electromagnetic torque generated by the rotor will no longer be zero, the rotor will push along the direction of spin.