Study on Temperature-Insensitive Permanent Magnet Eddy Current Retarder Using Magnetic Shunt Compensation Method

In this article, a novel permanent magnet eddy current retarder (PMECR), with a characteristic of temperature-insensitive damping torque over a wide range of operating temperatures, is proposed for speed limit systems. A compensatory magnetic shunt is accomplished by utilizing the magnet cladding composed of iron-nickel (Fe-Ni) alloy, and it is used to equalize the adverse effects of temperature sensitivity of the magnet remanence and the conductor disk conductivity on damping torque. Based on the 3-D finite element method, the suppression effect of compensating magnetic shunt design on the sensitivity of torque to operating temperature has been verified, and the influence of main structural parameters is studied. Moreover, experiments with different compensation structures are conducted, varying the rotational speed and changing the operating temperature within the range of 20 degrees C-150 degrees C. The experimental results validate the accuracy of the simulation model, and the achieved quantitative indicator of torque temperature sensitivity is less than 0.023%/degrees C. Additionally, compensatory capabilities are determined for the potential range of cladding thickness in engineering. With the compensatory magnetic shunt, similar devices can maintain torque stability with the dynamic wide change of the operating temperature.