Cogging Torque Reduction of Dual Stator Machine Using Hybrid Magnet Excitation

This article presents a method to reduce cogging toque for dual stator machine (DSM) using hybrid magnet excitation (HMDSM). HM excitation is composed of a ferrite magnet on the outer stator and a NdFeB magnet on the rotor, in which NdFeB magnet is applied to build main magnetic field for torque production, and the ferrite magnet serves as the second permanent magnet (PM) excitation source to reduce cogging torque mainly. The cogging torque of HMDSM is investigated using the energy-based method, in which analytical modeling of a representative HMDSM with two consequent-pole PM excitations is provided. For a comparison, DSMs with single and dual NdFeB magnet excitation are designed and analyzed to verify the merits of DSM using HM excitation. Analytical results show that cogging torque of DSMs can be minimized when PM with 0.5-T remanence is used on the outer stator. The configuration and key design parameters of DSMs are described, followed by torque characteristics calculated using finite-element analysis (FEA). The experimental results validate the analytical and FEA-calculated results, which show that the cogging torque of DSM can be decreased significantly using HM excitation.