Finite-element computation of nonlinear magnetic diffusion and its effects when coupled to electrical, mechanical, and hydraulic systems

Finite elements are used to compute eddy currents and magnetic diffusion times in steel cylinders with nonlinear B--H curves. Computations are made of diffusion times versus current in a typical axisymmetric magnetic actuator, showing good agreement with recently published approximate analytical formulas. The computed nonlinear diffusion times are then used to derive an equivalent resistor that is used in a model of an electrohydraulic system. The diffusion time causes delays in the coupled mechanical and hydraulic responses.