Analysis of Air-Gap Magnetic Field and Structure Optimization Design of Hollow-Cup Motor

Hollow-cup motors are usually used in spacecraft because of their low power consumption and high control accuracy. However, the air-gap between permanent magnets (PMs) rotor hollow-cup motor is uniform, sinusoidal characteristic magnetic field waveform inferior total harmonic distortion (THD) large, resulting torque ripple. For large motor, existing methods for optimizing characteristics air gap change shape PMs, but changed PMs difficult to manufacture magnetize, being limited not able achieve ideal optimization effect motor. Based on inner outer rotating synchronously during operation, a new structure design with an eccentric proposed instead changing PMs’ shape. Firstly, mathematical model established. Then, FEM shows that rotor’s eccentricity can bring closer effectively reduce THD. Finally, prototype optimal value made experimental verification.