Development of a novel Coaxial Magnetic Gear

Magnetic Gears (MGs) offer many advantages compared to mechanical gears such as reduced maintenance, high reliability and inherent over load protection. Among various MGs, a Surface Permanent Magnet (SPM) type Coaxial Magnetic Gear (CMG), which may be accepted to be a classical CMG, is may be preferable owing to its high torque transmission capability. The main drawback of this CMG is that the gear ratio as well as efficiency is highly affected by the speed increase due to severe Eddy current losses in permanent magnets. Having permanent magnets on the outer side of the rotor is another drawback of the classical CMG since these magnets are experience sever centrifugal forces as the speed increases and thus the MG may encounter serious damages. In order to overcome the mentioned drawbacks of classical CMGs, this paper introduces a new type CMG whose inner part contains interior permanent magnets (IPMs) rather than SPMs. A finite element based tool has been used to design the proposed magnetic gear and its performance has been investigated and compared with those of conventional CMG for various speed conditions. According to the analysis results, decrease in gear ratio with respect to the speed is significantly suppressed and thus efficiency is improved. Additionally, proposed CMG provides less amount of torque ripples.