Abstract
Magnetic couplings possess the nature of transmitting torque from a primary drive to a secondary follower by magnetic force with no mechanical contact. In addition to torque-transmitting capability, the factors that influence the transmission performances of magnetic couplings include the torsional stiffness, effects of iron yokes, misalignment, vibration suppression, damping effect induced by eddy current, cross coupling between two sets of magnetic couplings installed in limited space, and limitations of application environments, etc. The literatures those are relevant to magnetic couplings for the last two decades are reviewed in detail. Various analytical and finite element methods are introduced and compared, and their applicable conditions are identified.In this study, the method of equivalent magnetic charge is first employed for the analysis of the variations of the transmitted torque due to each type of misalignment. Subsequently, by using the technique of current sheet model, the analytical solution for predicting the field distribution and the transmitted torque of a cylindrical magnetic coupling with soft-iron yokes has been developed and verified. The results obtained from analyzing a multilayer model are used to determine both magnetic fields and the transmitted torque of a magnetic coupling. This analytical method has definite physical sense and provides an accurate means to predict the performance of magnetic couplings. It also possesses the advantage of short computation time. For the purpose of verifying the static and dynamic characteristics of the designed coupling, a test rig was constructed for the experimental study. Eventually, a designed magnetic coupling is applied to the transmission module of the wafer transferring system of a type of semiconductor equipments for high vacuum or ultra-clean processes.