Flux Synthesizing Linear Induction Motor with Super Multi-Phase Switching.

Abstract

Authors have proposed a novel concept of structure and control of linear induction motors (LIMs) named “Flux Synthesizing Linear Induction Motors (FSLIMs)”, where each slot has a conductor carrying an electric current whose amplitude and phase angle are controlled with super multi-phase switching devices. It is well-known that a LIM has the merits of direct drive and simple structure. A conventional one has, however, low power factor and energy efficiency; the end-effect is one of the significant reasons for the bad characteristics. Strategies against the effect have been limited by conventional three-phase windings. On the other hand, high-speed power switching devices are available with a reasonable cost. A super multi-phase drive enables more freedom for controls with the proposed structure of the FSLIM. Basic characteristics of a tubular test LIM with twelve slots have been measured and calculated to investigate an appropriate flux synthesis. As results, an appropriate switching scheme, which synthesizes sinusoidal distribution of the gap flux density, enables to suppress the end-effects, and to improve, consequently, the energy efficiency. In addition, basic conditions for the field-coordinateds oriented control of a thrust force are satisfied by keeping the amplitude of a gap flux constant with the flux synthesis.