Design and analysis of a two-stage transmission magnetic-geared machine

Abstract

The purpose of this paper is to realize a two-stage transmission magnetic-geared (2-STMG) machine with high gear ratio. The proposed machine contains a concentric magnetic gear (CMG) and a Vernier machine (VM). Both the components meet the magnetic gearing effect and share a common high-speed rotor (HSR). The VM is the first stage, and the CMG is the second stage. The designed gear ratio of the proposed 2-STMG is 34. The magnetic flux is partially coupled to the HSR yoke. The cogging torque on the HSR is slightly higher than that on the low-speed rotor (LSR). A method is presented to detect the gear ratio of magnetic geared machines with the back-electromotive force (back-EMF). And the evaluated gear ratio of the prototype is found to be close to the design value. The amplitude of the fundamental back-EMF is nearly linear with the LSR speed, and the slope of the fitting curve is ∼0.16 V/rpm. The peak static torques on both rotors are positively correlated with the DC currents applied to windings but limited by saturation when current is larger than 4A. The 2-STMG machine is controllable, and the speed ratio of HSR to LSR is close to the gear ratio of the outer CMG. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.