A new pole-changing winding using star/star-delta switching

A new pole-changing winding using star/star-delta switching is developed and is shown suitable for wide pole-ratio single-winding induction motors with pole combinations of the form (i) even/even and (ii) odd/odd pole pairs. Examples of 1:5 and 5:1 pole ratios are presented. Test results on laboratory-size machines for these pole ratios confirm the usefulness of the proposed schemes. The proposed arrangements are found to be superior to earlier designs in respect of either MMF/harmonic content or frame utilisation at both the pole settings. Change of speed is obtained using only six terminals and a control gear which is even simpler than the one used for any other pole-changing 3-phase winding.