A variable speed magnetic gear box using contra-rotating input shafts

This paper presents analytical, simulation, and practical analyses of a variable speed magnetic gearbox (MG) that uses contra-rotating (CR) input shafts. The CR turbine comprises two sets of rotors one behind the other: one rotor rotates in a clockwise direction while the other rotor rotates in an anticlockwise direction. Our magnetic gear magnetically combines the two CR input shafts into a single variable speed output shaft, and consists of three rotating parts: two contra-rotating low-speed input shafts and a single high-speed output shaft. Theoretical analysis is presented to show how to control the speed of the output shaft via control of the speeds of the two input shafts. This analysis is then supported by simulation and experimentation. The paper discusses the MG torque transmission capability by presenting pull-out torque test results and efficiency information when being driven through the different load torque shafts. The effective ratio of the MG is explained in terms of its torque curve result. A prototype gearbox was built, having been designed with an electromagnetic finite-element software package, and evaluated using a practical test rig.