3-D Analytical Model for Axial-Flux Eddy-Current Couplings and Brakes Under Steady-State Conditions

This paper presents a 3-D analytical model for axial-flux eddy-current couplings and brakes, leading to closed-form expressions for the torque and the axial force. The proposed model is valid under a steady-state condition (constant speed operation). It takes into account the reaction field due to induced currents in the moving conducting part. In order to simplify the analysis, we adopt the assumption of linearization at the mean radius, and the problem is then solved in 3-D Cartesian coordinates (curvature effects are neglected). The solution is obtained by solving the Maxwell equations with a magnetic scalar potential formulation in the nonconductive regions (magnets and air gap) and a magnetic field strength formulation in the conductive region (copper). Magnetic field distribution, axial force, and torque computed with the 3-D analytical model are compared with those obtained from the 3-D finite-element simulations and experimental results.