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.