New wide-ratio pole-changing motors

Parallel coil redistribution, a new method of wide-ratio pole changing, which is applicable to nontriplen pole ratios, is described with reference to an 8/2-pole 3-phase winding in 36 slots. The initial 8-pole setting is a standard winding. For pole changing, the coils are redistributed among the phases according to their 2-pole phase angles without reversing any part, obtaining a complete and balanced 2-pole winding out of each 8-pole phase. The connections are series delta at eight poles and 3-parallel delta at 2 poles, suitable for constant-torque drives. The tapped delta connection method used requires only nine winding leads to be brought out of the machine. The electromagnetic effectivenesses are 1.000/ 0.742. A comparison of the design with existing designs of 8/2-pole machines is given and test results on an experimental machine are reported.