Forces on semi-infinite overlapping rectangular poles: infinitely permeable against saturable case

Abstract

Magnetic fields and forces are determined for the simple, but important, idealised configuration of two overlapping rectangular poles of infinitely permeable iron by integration of expressions derived from a Schwarz–Christoffel transform. The force depends on three variables, the MMF, the gap, and the overlap, and can be expressed as a single-valued dimensionless function of the overlap to gap ratio. Results are compared with a previous study of the same configuration but with ideally saturable square M/H pole material, of which the work presented can be considered a limiting case as the ratio of MMF/gap decreases. When compared at similar flux densities and MMF, the transverse force with saturable poles at positive overlaps is seen to be about twice the force with infinitely permeable poles. The meaning and significance of this so-called ‘force augmentation with saturation’ is discussed in some detail.