Patent ID: 8564167

Claim:
In a three-phase, multi-speed electric induction motor having a 2n-pole, higher-speed mode and a 4n-pole, lower-speed mode, where n is an integer greater than or equal to one, wherein the motor comprises a stator core assembly presenting axial slots and defining a central axial bore for receiving a rotor assembly, with n pair of main winding coil groups corresponding with each phase being disposed within the slots of the core assembly, and wherein the main coil groups are energized, with the main coil groups within each phase being connected to one another in serial form, when the motor is in the lower-speed mode, the improvement comprising: a selectable extra winding coil group corresponding with each main winding coil group, said selectable extra winding coil groups being disposed within the slots of the core assembly, said main coil groups and said selectable extra coil groups both being energized, with the main coil groups within each phase being connected to one another in parallel form and the selectable extra coil groups within each phase being connected to one another in serial form, when the motor is in the higher-speed mode.