Rotational speed dependent motor properties

Abstract

The coils of alternating current (AC) motors experience back electromotive force (EMF) at high rotational speeds, which acts against applied voltage and drops motor efficiency steeply. By reducing the magnetic flux surrounding the coil of the stator, back EMF can be reduced and motor efficiency can be maintained at any rotational speed. Several prototypes that take advantage of centrifugal force and moving motor components are created; the prototypes prove that high overall magnetic permeability is achieved at low rotational speeds, and low overall magnetic permeability is achieved at high rotational speeds. In the more successful motor prototype, magnetic flux simulation results show a 43.5% reduction in peak values of back EMF.