When the interlock switch 63 makes the motor driving circuit 62 and the stator windings 311 of the permanent-magnet synchronous motor 3 closed-circuiting and makes the resistance controller 64 and the stator windings 311 of the permanent-magnet synchronous motor 3 open-circuiting, the energy storage device 72 supplies operation electrical energy through the motor driving circuit 62 to the permanent-magnet synchronous motor 3, making the permanent-magnet synchronous motor 3 operating in the second operation mode (namely the motor mode) to induce an acceleration on the external rotor 32.

Further, a power changeover circuit 73 may be connected with the energy storage device 72 and the power supply circuit 4 to selectively switch from the energy storage device 72 or the alternate-current power supply (ACV) to the permanent-magnet synchronous motor 3 for supply of electrical energy.

When the permanent-magnet synchronous motor 3 operates in the second operation mode, the electricity generation winding 312 similarly generates a backward charging voltage that is fed through the second rectifier and filter circuit 313 to the charging circuit 71, and the charging circuit 71 then generates backward charging electrical energy supplied to the energy storage device 72 to implement charging and energy accumulation in the energy storage device 72.