Current limited optimal excitation of magnetically coupled linear variable reluctance motors

This paper explores the design of excitation current profiles for a type of three-phase magnetically coupled linear variable reluctance motor. A model relating force production to air gap geometry is derived using magnetic circuit analysis under an assumption that flux flows across the air gap through tubular paths bounded by straight lines and circular arcs. Constrained optimization techniques are used for two purposes: first, to determine the motor´s continuous force limit corresponding to some given continuous current limit; second, to determine currents that satisfy the current limits and produce a desired force with minimum power dissipation. The optimization results indicate that a 6-wire connection is preferable to a 3-wire connection, and that wide teeth are preferable to narrow teeth, if the goal is to maximize the range of ripple-free force.