The Effects of Magnetic Circuit Geometry on Torque Generation of 8/14 Switched Reluctance Machine Senad Smaka, Mirsad Cosovic, Semsudin Masic University of Sarajevo Faculty of Electrical Engineering Sarajevo, Bosnia and Herzegovina ssmaka@etf.unsa.ba; mcosovic@etf.unsa.ba; smasic@etf.unsa.ba Abstract — The effects of magnetic circuit geometry on torque generation of switched reluctance motor with higher number of rotor poles are investigated in this paper. Specifically, the torque generation of novel switched reluctance machine with 8 stator and 14 rotor poles (SRM 8/14) is explored. A few suggested values of design ratios are derived for this novel SRM. The machine characteristics are computed using two-dimensional finite element method (2-D FEM). Keywords-switched reluctance machine; design parameters; finite element method. I. INTRODUCTION In the last decades, switched reluctance machine (SRM) has become an important alternative in various applications, in particular for vehicle propulsion and wind power conversion. Some of the most important advantages of SRMs are simple construction with no permanent magnets or windings on the rotor, low manufacturing cost, robustness, suitability for high speed operation, high reliability, simple cooling, and low maintenance. High torque ripple, acoustic noise, vibrations, EMI noise generation, numerous wires between machine and converter, and special converter topology are major disadvantages of SRMs. Also, SRMs have highly nonlinear and complex behavior due to local and bulk saturation in various parts of the stator and rotor cores. This affects the overall efficiency of the switched reluctance motor drives and makes them slightly less favored candidates over the commonly used permanent magnet synchronous machine and induction machine [1]. Therefore, advancements in SRMs design and control are necessary to boost the level of acceptance of these machines. Several novel configurations of SRMs that are presented recently open the possibility to improve characteristics of switched reluctance machines. These novel configurations have higher number of rotor poles than stator poles. They are based on new pole design formula presented in [1] and [2]. References [3] and [4] investigates the performance of two novel configurations of SRMs for traction applications. It is shown that the novel configurations of SRMs can have better performance in comparison to conventional switched reluctance machines. In this paper, a novel four-phase SRM with 8 stator and 14 rotor poles (SRM 8/14) is investigated. The machine configuration is described in Section II. The effect of the rotor outer diameter, the stator and rotor pole taper angles, the stator yoke width, the stator and rotor pole arc angles, and the rotor pole height on torque generation is explored. The results of 2-D FEM parametric analysis are presented in Section III. Finally, the conclusions are given in Section IV. II. SRM CONFIGURATION SRMs are typically designed as regular machines in which the rotor and stator poles are symmetrical about their centerlines and equally spaced around the rotor and stator circumference [5]. Regular machines can have three to seven phases and various combinations of stator and rotor poles [1]. Usually, conventional SRMs have the number of rotor poles N r computed as r s 2 N N   (1) where N s is number of stator poles. Pole design formula presented in [1] and [2] proposed a new relationship between number of stator poles N s and maximum number of rotor poles r s 2 2 N N   (2) where N s is even number greater than 4. The SRM 8/14, considered in this paper, is regular four- phase configuration with number of rotor poles calculated by (2). This machine has maximum torque zone of 12.857° mech and stroke angle of 6.428° mech . Number of strokes per revolution is 56. Fig. 1 shows part of the SRM 8/14 cross-section with main geometrical parameters emphasized. Rotor is shown at the unaligned position with respect to the phase A. The coils on two opposite stator poles are connected in series, thus forming phase winding with number of turns N ph .