A study to determine the act of excitation current on braking torque for a low power eddy current brake

Abstract

Eddy currents are induced by the nature of alternating flux related to the frequency of the change. In Eddy currents brakes, no precaution is taken in order to set the currents free to flow. In linear applications, Eddy current brakes are used to slow down a moving object by the produced braking force. In rotating applications, mostly braking torque is used to load a motor to be tested. In load tests, a conductive disk is attached to the rotating shaft of a motor which is placed in front of an unclosed magnetic path to permit the Eddy Current to be induced. The unclosed path consists of a magnetic yoke having poles placed on it which are surrounded by windings. Magnetic flux completes its route over the conductive disk whilst causing the Eddy currents to be induced. Eddy currents lead to a breaking torque related to magnetic coupling which is affected by a number of variables. Although the variables which are disk geometry, angular speed, material properties etc. are wellknown, the exact relation between the input and output quantities is still completely uncertain. In this paper, the effect of the change in excitation current to produce the magnetic flux is analysed for the wounded Eddy current brakes, in order to see the advantage of magnetic flux adjustment on braking torque. A previously obtained optimal design is analysed by finite elements method (FEM) for a different number of excitation currents so as to obtain the effect on output data.