Design and analysis of coaxial magnetic gear considering rotor losses

In recent years, coaxial magnetic gears (CMGs) are particularly attractive for applications desiring high torque density, such as electric vehicles and wind generators [1]. They can offer several advantages like low acoustic noise, maintenance free, and inherent overload protection in comparison with conventional mechanical gears. However, because of the modulation effect by the stationary ring, the magnetic fields produced by either the outer or inner rotor permanent magnet (PM) have many sub-harmonics, which lead to high PM eddy current (EC) loss and iron core loss. Notwithstanding the use of silicon steel sheet, the outer rotor loss of CMGs can´t be neglected. The purpose of this paper is to propose a novel rotor structure for CMGs to reduce the rotor losses, based on the limitation of sub-harmonics.