Analysis of a transient nonlinear 3-D eddy current problem with differential and integral methods

The paper compares the features of integral and differential formulations for the solution of of transient eddy current problems in nonlinear media. The integral method used reduces the nonlinear eddy current problem to the analysis of an equivalent network. Two dual edge element differential formulations are also used. Their field estimates automatically verify Faraday's and Ampere's laws and furnish the distribution of the constitutive error in the solution domain, which provides a useful tool for the refinement of the discretization. The methods are applied to analyze a massive magnetic circuit characterized by the presence of soft and hard magnetic materials with narrow gaps.