Experimental Verification of Critical-Speed Increase of Single-Phase Induction Machines via Winding Reconfiguration With Solid-State Switches

The concept of online electronic switching of windings will be applied to a single-phase induction motor with two separate windings with different pole numbers p₁ = 4 and p₂ = 6 and an auxiliary winding required for starting. During switchover from the low-speed winding to the high-speed winding, and vice versa, lasting less than a few milliseconds, small electrical torque and speed transients occur. Relying on closed-loop speed control, a smooth speed response is measured. This concept is, therefore, applicable to variable-speed drives, where a large speed range is desirable. Test data indicate that a speed-control range from 600 to 4000 r/min is obtainable with a single-phase induction motor.