On the modeling of poly-phase electric machines through Vector-Space Decomposition: Theoretical considerations

The possibility of equipping the stator winding of an electric machine with more than three phases is an increasingly important strategy in today´s drive design for its beneficial implications in terms of power rating, reliability enhancement and design degrees-of-freedom. Vector-space decomposition (VSD) is an important technique recently introduced for poly-phase machine modeling and analysis. A consolidated VSD technique exists covering symmetrical poly-phase machines, where the n stator phases are displaced by 360/n electrical degrees apart; conversely, other poly-phase configurations cannot be reduced to such a scheme and require some more dedicated treatment. Particularly, this paper shows how the VSD method can be effectively extended to poly-phase windings where a half phase progression (equal to 180/n electrical degrees) is used, as typically occurs in split-phase machines.