Analysis of Torque Production in Variable Flux Reluctance Machines

In this paper, the torque production mechanism of variable flux reluctance machines (VFRMs) is investigated. Initially, based on an analytical instantaneous torque model developed from the Lorentz force law and airgap field harmonic analysis, the magnetic gearing effect is revealed in the torque production of VFRMs. Then, by using a 6-stator-pole/4-rotor pole (6s/4r) VFRM as an example, all its torque components, including synchronous torque, reluctance torque, and cogging torque, are analyzed separately under linear condition. Their average torque and torque ripple characteristics are comprehensively illustrated. Finally, the influence of saturation effect is also accounted for with the help of finite element and frozen permeability methods. The analysis results are verified experimentally.