Optimal Design of Adjustable Air-Gap, Two-Speed, Capacitor-Run, Single-Phase Axial Flux Induction Motors

-In this paper, a new optimized structure for two-speed, capacitor-run, single-phase axial flux induction motor (AFIM) for direct-drive operation is presented. Although, there are many advantages for direct-drive systems, their axial forces between the stator and rotor increases with reduction in air-gap length and is of serious concern. An increase in the air-gap length will result in the deterioration of performance characteristics of the motor. In this paper, a new construction technique is proposed to fabricate an AFIM with adjustable air-gap length. After presenting a comprehensive design algorithm, all geometrical dimensions and electrical equivalent circuit parameters are analytically calculated. Then, a multiobjective and multivariable optimization for a high efficiency and power factor with minimum usage of core materials is carried out. Optimization process is verified using three-dimensional, time-stepping finite-element analyses, and finally, the prototype of the optimal motor is fabricated and tested. Good agreements between analytic, finite element, and experimental results show the success of the proposed design.