Innovative permanent-magnet starter motors for automotive micro-hybrid applications

This paper provides a review of several original improvements of 6-ferrite 12-V brushed DC starters, based on unconventional uses of Halbach arrays. Electromagnetic behaviors are firstly analyzed, especially when specific to this saturated high-current automotive application; hence the armature magnetic reaction and its link to commutation. After explaining which properties of Halbach arrays can be exploited, each novel design is detailed. Prototypes have been built and tested, so all three variants of motors are validated, whatever the type of material implemented, sintered or bonded magnets, even combined with an ironless armature instead of the usual slotted and laminated one. The proposals appear more expensive, but occur to be a great help to applications, showing enhancements in dynamic performance and brush durability, as two mandatory key features for modern starting systems.