MODELLING VERY SMALL AIR GAPS BETWEEN MAGNETIC SURFACES IN FINITE‐DIFFERENCE FIELD SOLUTIONS Available to Purchase

The finite‐difference discretization required to model accurately very small air gaps between ferromagnetic surfaces can be enormous. Provided the surrounding permeability is high, a simple representation of the air gap can be formulated within a finite‐difference equation, thus substantially reducing the number of nodes required. The method is applied to the determination of the force on a rectangular magnetic filler bar in the centre slot of the pole face of a turbogenerator rotor.