THE EFFECT OF NON-UNIFORM AIR-GAP ON THE NOISE IN SWITCHED RELUCTANCE MOTORS

The major problems in switched reluctance motors (SRMs) are radial force and torqueripple which cause increased undesirable acoustic noise. This paper describes an approach todetermine optimum magnetic circuit parameters to minimize both radial force and torque ripple forsuch motors. There is no publication for simultaneous reduction of both radial force and torqueripple. In previous works, torque ripple was decreased without any research on the radial force orcounter. In this paper, a procedure for radial force and torque ripple reduction in SR motors isproposed. To decrease the acoustic noise, the air gap width is increased while the radial force ismaximized. On the other hand, by increasing the air gap width, torque decreases. By varying theangular interval and consequently the air gap width, the optimum angular interval is achieved. Inthe optimum angular interval, the radial force decreases while the torque remains constant. A twodimensional (2-D) finite element (FE) analysis carried out on the 6/4 SRM. By using the methodof the compensated current, the ripple torque can be reduced to zero, radial force decreases 3.7%,and the acoustic noise power decreases 7.3% in the non-uniform air gap in comparison with thestatic case. Radial force decreases 5.6% and the acoustic noise power decreases 10.9% in theuniform air gap in comparison with the static case.