3-D finite element time-varying fields and eddy currents in nonlinear thin steel channels

A method for three-dimensional nonlinear transient eddy current and field computations in thin steel channels separated by air gaps is presented. The nonlinear thin steel plates with narrow gap were placed over a coil which is excited from a time-varying source. Details of the formulation for the nonlinear problem and the time derivative are given. The current amplitude was large enough to saturate the steel parts. The time constant of the excitation function was chosen so that large eddy current density is produced. Experimental data of flux density and eddy current density at specified test points in the analyzed volume were compared with numerical results. Excellent correlation between numerical and experimental results was achieved.