Determination of the effect of conductive disk thickness on braking torque for a low power eddy current brake

Abstract

In Eddy current brakes, mechanical energy is converted into thermal energy and the system is mainly an electromechanical conversion device. A rotating conductive disk is placed in front of calculated number of pole surfaces that create a magnetic field which is unchanged according to time. Since the disk rotates, a relatively changing magnetic field passes through the conductive disk causing Eddy currents to be induced inside the disk. These induced Eddy currents produce an opposing magnetic field forcing the rotating disk to slow down by means of consuming mechanical energy. Mathematical analysis of the effects of Eddy currents is almost impossible due to the complexity of both the magnetic problem and geometry. There is no obtained certain relationship which can explain output data in terms of input data since the relation includes too many variables including disk areas, disk thickness, disk radius, speed, etc. In this study, different eddy current brake designs are analysed where all design constraints were kept unchanged apart from conductive disk thickness to determine the effect of change. All mentioned designs are analysed by commercial software using finite element method (FEM). Torque vs. speed, total power dissipation vs. speed characteristics for low, medium and high speed regions and change of critical speed and maximum braking torque according to conductive disk thickness are also obtained.