Theoretical and experimental research on hybrid-magnetic-circuit multi-couple motor

A novel hybrid-magnetic-circuit multi-couple motor is put forward to compensate for the uneven axial distribution of the air-gap flux density produced by the permanent magnet in traditional hybrid stepping motor. The structures of the hybrid-magnetic-circuit multi-couple motor are given. The analytical model is established, and the torque equation is deduced. FEM (finite element method) is used to analyze the air-gap flux density distribution and optimize the axial field coil. Experiments were done to a prototype motor and an autocycle motor. FEM calculation and experiment indicate that with the existence of additional axial field coil, the axial distribution of the air-gap flux density is more even in the hybrid-magnetic-circuit multi-couple motor than in the traditional hybrid stepping motor. Calculation and experiment show that the maximum static torque of the hybrid-magnetic-circuit multi-couple motor is much higher than that of the traditional hybrid stepping motor of the same volume, i.e., the hybrid-magnetic-circuit multi-couple motor can improve the torque to volume ratio. FEM calculation also indicates that the optimum axial field coil length is approximate making it extend into 2/3 of the iron core lamination length.