A NEW INVERTER CONTROL SCHEME FOR INDUCTION-MOTOR DRIVES REQUIRING WIDE SPEED RANGE

A new control scheme to extend the speed range of a four-pole inductio n machine is investigated. A three-phase stator winding is used with e ach of two coil groups per phase being independent resulting in a six- coupled circuit, six-terminal stator winding. Two inverters supply the machine with the required regulated currents to obtain the effect of either four-pole or two-pole windings. Four-pole operation is proposed from zero speed until the end of its constant power region. Employing contactorless pole changing to obtain two-pole operation extends the constant power region resulting in a doubling of the speed range for a pproximately the same inverter/machine rating.