4th Power Electronics,Drive Systems & Technologies Conference (PEDSTC2013),Feb 13-14,2013,Tehran,Iran High Effcient Torque Control of Switched Reluctance Motor Taking Nonlinear and Saturation Effects into Account M.Dowlatshahi, S.M.Saghaian-Nejad,M. Afshoon Electrical and Computer Engineering Department Isfahan University of Technology (IUT) Isfahan, Iran Dolatshahi@ec.iut.ac.ir Abstract-Torque pulsation mechanism and highly nonlinear magnetic characterization of switched reluctance motors (SRM) lead to unfavorable torque ripple and reduce the variety of applications in industry. In this paper, a torque sharing function (TSF) is proposed considering magnetic saturation effects as well as minimizing power loss during the commutation region. Constant torque trajectories are considered in phase currents plane based on nonlinear T-i-theta curves which are obtained by experimental measurements. Optimum points selection on constant torque trajectories are based on improving drive efciency and minimizing copper loss in each rotor position. This has been achieved by fnding the tangent intersection between the constant curves and a circle with minimum radius in entering and outgoing phase currents plane. Compared to conventional TSFs, the resultant reference current from the proposed method has less peak and effective values. Moreover, it also has acceptable performance especially in high torque low speed applications. An experimental four phase 1.6 K, 8/6 SRM set of magnetic characterization data used to simulate and validate the effectiveness of the proposed method. Keywords-Torque Control; Switched Reluctance Motor; Power Loss Minimization; Saturation effects I. INTRODUCTION Switched reluctance motor (SRM) is a double salient motor with no winding or pennanent magnet on rotor. It has rugged and fault tolerant structure with the most robust and reliable constructions [1]. Due to the simple structure, low manufacturing and repairing costs as well as ability to operate in wide range of temperature, SRM has been taking into accounts more recently. One of the most drawbacks in switched reluctance applications is high torque ripple compared than other ac type machines [2]. Torque pulsation mechanism and high saturated nature of magnetic characterization can cause undesirable torque ripple and deteriorate drive perfonnance especially in high precise industrial applications. In order to suppress torque ripple many investigations have been done recently and many torque control techniques introduced [3]-[9]. Even though design approaches were taking into consideration in [3],[4] to produce constant torque and minimizing torque ripple, control 978-1-4673-4484-5/13/$31.00 ©2013 IEEE 49 Jin Who Ahn Mechatronics Engineering Department Kyungsung University Busan, Korea techniques have been more considered to control the total torque in conventional existing switched reluctance motors. One of the most convenient approaches is coordinate incoming and outgoing phase torque so that the total torque remains constant during the commutation between phases. Torque Sharing Function (TSF) is a well known torque control alterative in which reference torques for individual phases defned assuming the total torque stays at constant level. Direct instantaneous torque control (DITC) is also the simple torque control concept. However, implementation of switching rules is complicated. Some of the conventional TSFs such as linear, cosine, cubic and exponential types reported in literature. Effective and peak phase curents, power loss and voltage requirements during the commutation would be some possible secondary objective fnctions to make an optimal TSF. However, having a lower power loss implies faster commutation between two adjacent curent phases and this may cause voltage saturation. Vujicic [9] introduced a family of TSFs using different secondary objectives such as power loss minimization and drive constraint taking into account. However, considering linear magnetic characterization and simple torque equation may cause to deteriorate drive efciency. Moreover, selecting the slope of inductance in linear or saturation region has greatest impact on effectiveness of this method especially for load torque near the rated value. In [8] a logical TSF proposed in which the outgoing phase current damped quickly and total torque remained constant using regulation of torque produced by incoming phase. However, the motor is considered in linear region and point selection on torque constant trajectories was based on general knowledge of user and decreasing the outgoing phase current. Increasing peak current and voltage stress are the other drawbacks of this method. In this paper, constant torque trajectory in phase current plane will be obtained using the completely nonlinear torque equation and considering saturation region of magnetic characterization. Power loss minimization will be assumed as secondary objective fnction. Aferwards, point selection on constant torque trajectory curves will be accomplished in favor of power loss reduction for each rotor position. Simulation results will be given to