Resistive torque in permanent magnet couplings operating through a conductive wall

Abstract

Purpose The purpose of this paper is to propose an analytical approach to determine the resistive torque caused by a conductive wall between the rotors of axial permanent magnet couplings. In this configuration, relative motion between the coupling rotors and the wall generates a resistive torque that is a consequence of the induced eddy currents in this barrier. Therefore, such induced resistive torque implies a reduction in the permanent magnet coupling performance, that is, its torque transmission capacity. Design/methodology/approach The developed resistive torque analytical formulation was based on eddy-current brakes of previous studies. To validate the proposed method, tests were conducted in a prototype and results were compared with analytical ones. Findings The analytical method showed a good correlation with the experiment data. Furthermore, a major degradation of the coupling capability to transmit torque was found because of the conductive wall presence, enhancing the importance of predicting such phenomenon when designing these devices. Originality/value A novel direct assessment of the resistive torque while in motion is presented in this paper. These measurements were of great importance to accurately compare the analytical and experimental data.