Around the silicon steel sheet, the shaft part is wound with two sets of coils, and a Hall induction module is used as a synchronous detection device to control a set of circuits, which make the two sets of coils wound around the shaft work in turn.  The silicon steel plate produces different magnetic poles, which generate a repulsive force with the rubber magnet.  When the repulsive force is greater than the static friction force of the fan, the fan blade rotates naturally.  Because the Hall sensor provides a synchronous signal, the fan blade is continuously operated in a direction determined by The Flemings right hand rule.