Study characterization and optimization of various parameters of permanent magnet eddy current braking system

Abstract

Friction brakes develop required braking force by friction between brake disc and pads or between brake drum and linings. However, there are several problems in friction brakes such as squealing noise, thermo mechanical failures, disc distortions, brake judder etc. Eddy current brakes works on the principle of induced magnetization. Eddy current brakes are made up of either electromagnets or permanent magnets. Eddy current brakes using electromagnets have many problems such as interference with signaling and control systems and being very expensive. Eddy current brakes using permanent magnets can be a better alternative. Permanent magnets are used to develop induced magnetization. The drag force depends on various parameters such as conductivity of the material, speed of conducting material in the magnetic field, flux density and projection area in the conductor. In the present work, an attempt has been made to understand the influence of various factors on the brake parameters using Neodymium Iron - Boron (NdFeB) magnets. NdFeB magnets are chosen for experimental investigations because of their higher remanence, higher coercivity and energy product. The magnets chosen are 50 mm in diameter and 12.5 mm thickness. Discs made of various conducting materials such as Aluminum, Copper and Brass is chosen for investigations because of their higher conductivity property. The thicknesses chosen are 4 mm, 6 mm and 8 mm. The speeds selected for investigations are 2000 rpm, 3000 rpm, 4000 rpm and 5000 rpm to simulate speeds of 75.39 Km/hr, 113 Km/hr, 150.8 Km/hr and 188.5 Km/hr as higher speeds generate more induced magnetization. Special purpose test equipment is developed and fabricated to carry out experimental investigations. The test equipment is interfaced with various sensors, microcontrollers and data acquisition systems and software. The entire operations of the test equipment are controlled through a computer. For carrying out the experiments, magnets have to be moved towards rotating conductor to simulate brake