Analysis, Design and Optimization of Hysteresis Clutches

Electromagnetic clutches are widely used devices in industrial applications when a torque must be transmitted between two components without mechanical contact avoiding friction and so reducing wear and maintenance time. Hysteresis clutches are a particular variant of electromagnetic couplers used when a constant torque from zero to the synchronous speed needs to be transmitted. This paper deals with the analysis, design and optimization of hysteresis clutches. After a brief introduction on the operating principle, a new method of analysis is then introduced. The latter allows a fast prediction of the performance of hysteresis couplers without sacrificing the accuracy of the performance evaluation even when adopting anisotropic magnetic materials. The introduced method, based on a static finite element simulation followed by a post-processing of the evaluated magnetic field, is then used within an automatic design procedure in order to identify the inevitable trade-offs encountered when optimizing the geometry of any hysteresis clutches with a given outer envelope. The obtained results are commented in-depth and allow to draw general design guidelines with special regards to the selection of the number of poles and the magnetic materials. The effect of the high level of anisotropy of the most common magnetic materials showing the highest energy density is carefully taken into account allowing to deduce the optimal preferred direction of magnetization.