Study on Analytical Model of Permanent Magnet Eddy Current Retarder for High Temperature Gas-Cooled Reactor

Abstract The permanent magnet eddy current retarder serves as the main rod drop speed-limiting device in the control rod drive mechanism of the pebble-bed modular high temperature gas-cooled reactor. It can dissipate the kinetic energy of the control rod drop by generating eddy currents in the rotating conductor disk. To achieve fast calculation and analysis of the damping torque, an analytical model was established for a typical simplified structure of the permanent magnet eddy current retarder. Firstly, the three-dimensional structure was simplified into a two-dimensional model, and a two-dimensional magnetic circuit was established based on the magnetic equivalent circuit method, then the magnetic reluctances and fluxes of the circuit were calculated. Secondly, based on Faraday law of electromagnetic induction law and Ampere’s circuital theorem, the eddy current-induced magnetic field was solved, and the damping torque was calculated based on energy conservation. Furthermore, a three-dimensional correction was made. Finally, the analytical model was validated through three-dimensional finite element simulation. The results indicate that the analytical model can effectively calculate the magnetic flux density distribution in the air-gap and the torque speed characteristics. Within the general parameter range, the variation characteristics of torque with structural dimensions can be accurately analyzed. In addition, the temperature influence can be effectively analyzed within the range of 20∼200 °C.