Studies of torque ripple in a switched reluctance motor under a controlled average torque value in a low-velocity mode

Abstract

In the case of adjusting the average torque value of switched reluctance motors, torque ripple is most pronounced in a low-velocity mode. In this mode, the motor phase-currents are usually forcibly limited; therefore, owing to the available voltage margin, by properly selecting the positions of phase switching, one can influence the shape of the phase-currents within certain limits and, thereby, achieve a decrease in the torque ripple. This paper considers the possibilities of reducing torque ripple using very common methods for restricting the phase-current, such as voltage control and current control. Using simulation modeling in the Matlab–Simulink environment, the best combinations of control actions are found, with which torque ripple is minimal. It is shown that, by using the first method of phase-current restriction, the reduction in torque ripple under certain conditions is achieved via a forced pulling of the range of phase-current increase due to a later switching on of the phase with a simultaneous increase in the voltage across this phase. In a number of cases, the desired effect can be achieved only owing to a certain delay in the command for switching the phase off with respect to the position corresponding to a single-switching mode. For the second method of phasecurrent restriction, the best switching conditions are found for fixed levels of current restriction determined from the desired values of the average motor torque, and independent adjusting of the switch-on and switchoff positions of its phases.