Introduction

Abstract

Magnetic devices have traditionally been designed by combining empirical rules based on experimental evidence with simplified magnetic circuit models. This technique may be labelled design by rule. But as devices become increasingly varied and complex, conventional design rules are no longer adequate and design by analysis, based on reasonably detailed solution of the underlying electromagnetic field problems, becomes the normal practice. Design by analysis really means design by numerical analysis since no other tools are capable of dealing with both the geometric complexity and nonlinearity found in such disparate devices as vertical recording heads and direct current machines. Design by analysis therefore inevitably means at least computer-aided analysis, and increasingly has come to mean full-fledged computer-aided design.