D.S. Schramm

Bio: D.S. Schramm is an academic researcher from Heriot-Watt University. The author has contributed to research in topics: Direct torque control & Inverter. The author has an hindex of 2, co-authored 2 publications receiving 169 citations.

Torque ripple reduction of switched reluctance motors by phase current optimal profiling

Abstract: Optimal precalculation of the position-phase current profile for current feeding a four-phase, 4 kW switched reluctance motor results in a single-input, linear, decoupled output torque controller that provides low torque ripple. A bicubic spline interpolation was used to model the nonlinear experimental data. The algorithm is based on minimizing both the average and peak current and hence improves the dynamic performance of the novel six-switch, current-fed, 4 kW, 40 kHz IGBT inverter. Test results are presented. >

Noninvasive speed measurement of inverter driven induction motors

Abstract: A frequency component in the stator current of the induction motor which is caused by rotor dynamic eccentricity is used for a noninvasive speed measurement. The frequency of this component is related to the rotor speed, and its bandwidth is related to the supply frequency and the phase-lock-loop RC filter cutoff frequency. In the case of an inverter drive, the signal can be extracted from the phase current reconstructed from the DC link current. The use of switched-capacitor filters allows a frequency component related to the rotor speed to be extracted from the DC link of variable-frequency, inverter-driven induction motors. >

Minimization of torque ripple in SRM drives

Abstract: The torque pulsations in switched reluctance motors (SRMs) are relatively higher compared to sinusoidal machines due to the doubly salient structure of the motor. The magnetization pattern of the individual phases together with the T-i-/spl theta/ characteristics of the motor dictate the amount of torque ripple during operation. Both machine design and electronic control approaches have been used to minimize the torque ripple in SRMs. This paper presents an extensive review of the origin of torque ripple and the approaches adopted over the past decade to minimize the torque ripple. A hybrid torque-ripple-minimizing controller that incorporates the attractive features of some of the techniques developed in the past decade is presented along with simulation and experimental results.

Torque ripple minimization in switched reluctance motor drives by PWM current control

Abstract: Higher torque ripple is one of the few drawbacks of switched reluctance motor (SRM) drives which otherwise possess excellent characteristics for applications in many commercial drives. This paper begins with an extensive review of torque ripple reduction methods that appear in the literature and then presents a new strategy of PWM current control for smooth operation of the drive. This method includes a current control strategy during commutation when torque ripple minimization is of utmost importance.

Optimization and Evaluation of Torque-Sharing Functions for Torque Ripple Minimization in Switched Reluctance Motor Drives

Abstract: Two improved torque-sharing functions for implementing torque ripple minimization (TRM) control are presented in this paper. The proposed torque-sharing functions are dependent on the turn-on angle, overlap angle, and the expected torque. This study shows that for a given torque the turn-on angle and the overlap angle have significant effects upon speed range, maximum speed, copper loss, and efficiency. Hence, genetic algorithm is used to optimize the turn-on angle and the overlap angle at various expected torque demands operating under the proposed TRM control in order to maximize the speed range and minimize the copper loss. Furthermore, four torque-sharing functions are used to derive the optimized results. At the same time, a fast and accurate online approach to compute the optimal turn-on and overlap angles is proposed. Therefore, this paper provides a valuable method to improve the performances of switched reluctance motor drives operating under TRM control.

DITC-direct instantaneous torque control of switched reluctance drives

Abstract: This paper presents an online instantaneous torque control technique for switched reluctance machines called direct instantaneous torque control. The method comprises two novel aspects. First, torque is estimated as a function of terminal quantities, i.e., flux linkage and phase current. Hence, torque estimation is independent of the rotor position. Secondly, high-bandwidth drive performance is obtained by implementing a digital torque hysteresis controller. Thus, the method works without torque profile functions and auxiliary phase commutating strategies. Therefore, the control algorithm offers a wide drive operating range without the use of a high-resolution shaft position sensor or sensitive position estimation techniques. Experimental and simulation results are presented in this paper.

Torque ripple minimization in switched reluctance motor drives by PWM current control

Abstract: Higher torque ripple is one of the few drawbacks of switched reluctance motor (SRM) drives, which otherwise possess excellent characteristics for applications in many commercial drives. This paper begins with an extensive review of torque ripple reduction methods that appear in the literature and then presents a new strategy of PWM current control for smooth operation of the drive. This method includes a current control strategy during commutation when torque ripple minimization is of utmost importance. >