A Novel Topology of Magnetic Gear

Over the past few years, magnetic gears (MG) have attracted much attention. The main reason is the contactless nature of torque transmission in contrast with mechanical gears, that leads to some advantages such as high reliability and low maintenance requirements [1]. Unlike a traditional permanent magnet synchronous machine, electromagnetic torque in MG is produced by the interaction between two separate sets of permanent magnets, resulting in very high torque density up to 239 Nm/L [2] under natural air cooling. These peculiarities of modern MGs makes them promising solution, especially for low-speed applications. Recent studies on MGs have shown that the most viable topologies in terms of torque density are so-called coaxial planetary MG [1] and cycloidal MG [3]. Coaxial planetary MG [1] has only two concentric rotating parts which execute a simple rotating motion. However, the main problem with this topology is the inherent low mechanical strength of modulator [4] that at the same time is supposed to withstand high torque. In contrast, the structure of cycloidal MG can is very robust, but a rotor of cycloidal MG experiences rotating motion about two axis simultaneously which is very challenging to utilize. These disadvantages of modern MG limits their industrial application. This paper proposes a novel topology of MG, which eliminates drawbacks of existing MG. Proposed MG utilizes a simple rotating motion of input and output shafts and lacks the weak modulator in the construction. In the first section of the paper, the structure of proposed MG (Fig. 1) is described and operational principle is discussed. Expressions for gear ratio and design considerations are presented. The second section of the paper presents a brief description of simulation method as well as results of modeling in static and quasi-static modes. Results of simulation show that proposed MG has high torque density (140 Nm/L) and is capable of transmitting constant torque with corresponding gear ratio. In the third section of the paper, the possible mechanical design of the novel topology of MG is presented, and its manufacturability is discussed. Finally, the work concludes that proposed MG topology has high torque density about 140 Nm/L and high level of utilization of permanent magnets about 860 Nm/L as well as more robust and reliable structure in comparison with existing topologies of MG.