Experience of finite element CAD for force prediction in magnetic actuators with small air-gaps

This paper presents practical results and experience gained in the use of a finite-element (FE) package to predict normal force in 'E-Core' electromagnets of various core lengths and for a range of operating air-gaps. The experiences reported are intended as a guide for other engineers, who are not FE experts, but wish to use such CAD tools for research and development. In particular, special attention is given to the simulation of the 'small air-gap' case where the gap length is many times smaller than the pole dimensions. Two aspects are highlighted: the difficulty of achieving good agreement between simulated and measured results and a quantitative comparison of two-dimensional and three-dimensional simulations.