Tilting torque analysis of an iron-cored tiered-type permanent magnet spherical motor

This article mainly studies the tilting torque characteristic of a novel iron-cored tiered-type permanent magnet spherical motor (T-PMSpM), which has the merit of large torque ability benefitted from the use of iron cores in both rotor and stator. However, the use of ferromagnetic materials also makes the iron-cored T-PMSpM much different from other air-cored spherical motors. Thus, the influence on the tilting torque characteristic is investigated theoretically and numerically. First of all, the active tilting torque is obtained based on a simplified model of air-gap magnetic field distribution. According to this model, the influence of the magnetic field distortion caused by the tilting motion is evaluated. Then, the characteristic of the restoring torque, which obviously exists in the iron-cored T-PMSpM and hinders the tilting motion, is analyzed under different working conditions. The three-dimensional finite-element analysis (FEA) is adopted to calculate the accurate output tilting torque. Finally, an experimental procedure is designed to measure the output tilting torque of the prototype motor for verification. The measured results are compared with the FEA results.