Investigation of the effect of pole shape on braking torque for a low power eddy current brake by finite elements method

Abstract

The principle of electromagnetic braking involves the conversion of kinetic energy into thermal energy. When a non-magnetic or magnetic conductive material rotates into static magnetic field, eddy currents are induced in material. Paths of induced eddy currents depend on the geometrical configuration of moving conductive material and also its electromagnetic properties. However, due to electrical resistance of the conductive material, the eddy currents are disrupted into heat and braking torque occurs. In practice, eddy current brakes are frequently used for motor testing because of the easiness of braking torque control. It is also used as supplementary retardation equipment in addition regular friction brakes on heavy vehicles. Mathematical analysis of the effects of eddy currents is almost impossible due to the complexity of electromagnetic problem. There is no obtained certain relationship which can explain output data in terms of input data since relation includes too many variables including conductive disk areas, conductive disk thickness, conductive disk radius, speed etc. In this study, braking effects of two different eddy current brakes having different pole shapes are compared. Round and rectangular pole shape which have the same pole area are analysed where all numerical design constraints were kept unchanged to compare braking torque vs speed characteristics and total power dissipation on rotating disk. All mentioned designs are analysed by commercial software using finite element method (FEM).