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 torque
ripple which cause increased undesirable acoustic noise. This paper describes an approach to
determine optimum magnetic circuit parameters to minimize both radial force and torque ripple for
such motors. There is no publication for simultaneous reduction of both radial force and torque
ripple. In previous works, torque ripple was decreased without any research on the radial force or
counter. In this paper, a procedure for radial force and torque ripple reduction in SR motors is
proposed. To decrease the acoustic noise, the air gap width is increased while the radial force is
maximized. On the other hand, by increasing the air gap width, torque decreases. By varying the
angular interval and consequently the air gap width, the optimum angular interval is achieved. In
the 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 method
of 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 the
static case. Radial force decreases 5.6% and the acoustic noise power decreases 10.9% in the
uniform air gap in comparison with the static case.