Miniature sheet-rotor induction motors for extremely high speeds

Electronically fed 2-phase motors capable of operating at speeds up to 150 000 rev/min are considered. Theoretical comparison is given between sheet-rotor and squirrel-cage induction motors having rotors of approximately 1 cm diameter. A design approach is presented for sheet-rotor machines, based on the fundamental rotating field, which relates performance to winding temperatures. Experimental results from a naturally cooled and a force-cooled motor are given. The validity of standard equivalent circuits is discussed and the effect of nonuniform airgap permeance presented.