The theory and applications of eddy currents induced in conducting materials by time-varying magnetic fields are reviewed. The mathematical methods employed in solving the relevant problems are presented. Both analytical and numerical methods are described. Applications based on effects arising from eddy currents are discussed in detail. These applications are to magnetic levitation, electromagnetic launching, hyperthermia treatment of cancer, and nondestructive testing. >

Eddy currents: theory and applications

Modeling and control of an eddy current brake

Analytical modeling of eddy current brakes with the application of time varying magnetic fields

Eddy current is a very important and intriguing phenomenon. A direct result of Lenz's law, it has been an integral part of research on electrical machines. The applications and associated research field of eddy currents are very widespread and virtually impossible to include in a singlestudy. Therefore this study tends to capture research trends in eddy-current loss analysis pertaining to the field of rotating electrical machines only. The research period taken up is from 1892 to 2010. The trends in research and application have been brought out. This study aims to serve as a reference guide to all those interested in the field of eddy-current loss analysis in electrical machines.

Literature survey of eddy-current loss analysis in rotating electrical machines

Modeling and Control of Eddy Current Brake

Analytical solutions are given for the eddy currents (magnitude and phase) induced in a cylindrical shell of infinite length and thickness by a 3-phase winding of finite length placed coaxially inside the shell. The flux densities and associated loss are also determined. Solutions are obtained in integral form by solving Maxwell's equations and applying appropriate boundary conditions. Use is made of the magnetic vector potential. The loss is calculated by applying Poynting's theorem on the internal surface of the shell. Numerical results are obtained on a digital computer for different radii of the shell by using the Gauss- Laguerre method. The limitations of the method are discussed. The conducting material is nonmagnetic and the solutions are valid for all frequencies smaller than those of the optical spectrum. Tests were made on an aluminium shell and measurements of field values in the air were compared with the corresponding theoretical results.

J.A. Tegopoulos

Papers

Eddy-current distribution in cylindrical structures caused by rotating magnetic fields