Analytical Prediction of Torque Characteristics of Eddy Current Couplings Having a Quasi-Halbach Magnet Structure

A generic analytical frame for evaluating the torque performance of eddy current coupling equipped with a quasi-Halbach permanent magnet (PM) array is given, where the motional eddy current problem is represented by a four-layer boundary value problem. The effective magnetic characteristics and the field equation associated with the quasi-Halbach array are described in detail. To effectively predict the actual electromagnetic force at any slip speed, the eddy current distributions in the low-speed and high-speed cases are, respectively, investigated, and a modified 3-D correction factor is subsequently developed. A verification process is implemented by a 3-D finite-element analysis using the fixed computational grid method. The effects of the thickness of PM back iron on the degree of saturation and then on the variation of torque are investigated, and the impact of the eddy currents induced in the conductor back iron on the overall torque in the whole slip-speed range is also assessed.