Electromagnetic torque ripples in the electrical drive with field regulated reluctance

The presence of the electromagnetic torque ripples in the drive with the field regulated reluctance machine (FRRM) is due to the current switching process in the stator windings occurring in time. The maximum value of the pulsations in the open loop scheme for the six-phase motor can be about 20% of the produced electromagnetic torque. One of the most usable analysis methods of the processes in the drive with the FRRM is the method of winding functions. This method allows you to calculate the ripples amplitude according to the average torque of the motor with a different number of phases. According to the calculating results the trapezoidal form of the current with the six phase number is the optimal solution in view of the drive cost, energy, weight and size data. If the number is less than six phases, the fluctuation amplitude increases significantly, this is unacceptable. On the other hand, increasing the number of phases over six would increase the equipment amount with a slight decrease in the pulsations amplitude. To suppress the electromagnetic torque ripples authors recommended to create and to use the high-speed current control loops (CCL) and to use the flexible positive current feedback in case of switching phase currents. Such a solution allowed to get the average value of the torque for 10% higher than in the system without correction and significantly reduced the amplitude of the electromagnetic torque ripples. The possibility of effective work of the electric drive with the FRRM in emergency conditions is shown.