The Mechanism How Coaxial Magnetic Gear Transmits Magnetic Torques between Its Two Rotors: Detailed Analysis of Torque Distribution on Modulating Ring

Coaxial magnetic gears (CMGs) have attracted increasing attention in recent years. The field modulation effect arising from modulating ring is considered as the reason why CMG can realize torque transmission between its two rotors. However, the magnetic torque interaction among modulating ring and two rotors is rarely investigated. Therefore, the purpose of this paper is to figure out the detailed torque distribution on the modulating ring, which plays a crucial role as the force/torque medium between the inner rotor and the outer rotor. First, the conceptual model, the operating principle, and the practical configurations of CMGs are introduced. Second, theoretical derivation of torque distribution on each surface of modulating rings with different connecting bridges is conducted by using the Maxwell stress tensor method. The calculation results match very well with those obtained from the traditional 'holistic analysis method' that is widely used in previous publications, and this validates our proposed 'detailed analysis method.' Third, how the connecting bridges affect the torque distribution on modulating rings is presented intuitively. Finally, three CMGs with inner bridge, outer bridge, and double bridges, respectively, are built for experimental verification.