Modeling and Simulation of a 16/12 Double Stator Switched Reluctance Motor

Cumhuriyet Üniversitesi Fen Fakültesi Cumhuriyet University Faculty of Science Fen Bilimleri Dergisi (CFD), Cilt:36, No: 3 Özel Sayı (2015) Science Journal (CSJ), Vol. 36, No: 3 Special Issue (2015) ISSN: 1300-1949 ISSN: 1300-1949 Modeling and Simulation of a 16/12 Double Stator Switched Reluctance Motor M. ASGAR1,*, E. AFJEİ1, M. M. MAHMOODİ2, A. R. BAHRAMİ3, M. A. FASİHİZADEH1 1Department of Electrical Engineering, Shahid Beheshti University, G.C., Tehran, Iran. 2Department of Electrical Engineering, Saveh Branch, Islamic Azad University, Saveh, Iran. 3Dep. of Electrical Engineering, Isfahan (Khorasgan) branch, Islamic Azad University, Isfahan, Iran Received: 01.02.2015; Accepted: 05.05.2015 ______________________________________________________________________________________________ Abstract. Modeling of a switched reluctance motor (SRM) is to predict the motor performance with a reasonable estimate over a wide range of speed and torque. Obtaining the realistic model of SRM which operates in a region of magnetic saturation due to complex structural implementation progress is too complicated process, with long response time. This paper introduces a linear model of double-stator SRM (DSSRM) which will be applied on directdrive washing machine application. The proposed method uses a developed simple magnetic equivalent circuit for modeling a DSSRM. The electromagnetic characteristics of the designed DSSRM are analyzed by finite element method (FEM) to validate the extracted results of the model. Finally, the experimental results with appropriate accuracy are achieved for modeling and magnetic analysis of the evaluated DSSRM. Keywords: Inductance profile, flux linkage, linear model, double-stator switched reluctance motors, finite element analysis 1. INTRODUCTION Nowadays, SRMs have been used for a wide range of various applications such as aerospace industry, marine propulsion systems, linear drives, mining drives, handheld tools, home utilities, etc. [1, 2]. The main reasons for using SRMs in these applications are low-cost construction characterized by an absence of magnets and rotor winding, fault tolerant power stage design and high level of performance over a wide range of speeds [3-5]. Reasonable cost and availability of the necessary electronic components make SRM as a viable alternative to other commonly used motors like induction machines, brushless DC (BLDC), permanent magnet (PM) synchronous or universal motors for various applications [6]. Despite all the advantages, in comparison with the PM or BLDC motors, the torque per volume or the efficiency of the SRM is not comparable [7]. Performance improvement of SRM is one of the interesting research topics to make it an applicable option to replace the PM or BLDC motor [8-11]. Different techniques have been used to enhance the efficiency of the SRM. Each method has its own advantages and disadvantages. Efficiency improvement in some methods is negligible, but some others can establish a significant improvement in efficiency [12]. Utilizing the segmented rotor and the double stator configurations are two effective approaches to improve the efficiency of the SRM. _____________ *Corresponding author. Email address: Special Issue: The Second National Conference on Applied Research in Science and Technology http://dergi.cumhuriyet.edu.tr/cumuscij ©2015 Faculty of Science, Cumhuriyet University ASGAR, AFJEİ, MAHMOODİ, BAHRAMİ, FASİHİZADEH 1.1 SEGMENTED ROTOR SRM The rotor structure of segmented rotor SRM (SSRM) composes of a series of discrete segments of laminated that are located on an aluminum or non-ferromagnetic cage. Therefore, each rotor segment is magnetically isolated from its adjacent segments. By replacing the conventional toothed rotor with individual segments, it has been verified that the higher torque density than the conventional SRM could be achieved [13]. In rotary SRM classification, depending on the total structure of SSRM, the rotor collection can rotate interior, exterior, or even middle of the machine structure. The stator structure of an SSRM is the same as conventional SRMs. The SSRM significantly improves the efficiency by eliminating the yoke on the rotor structure. This leads the rotor weight reduction, and makes shorter flux paths for the magnetic fields to reduce the current required and the number of phase winding turns. Moreover, decreasing the length of the flux path reduces the eccentric forces between the stator and rotor poles. The weak points of SSRM are related to the strength of segmented rotor holders, especially in high speeds, high temperatures, or in intense temperature variations applications. 1.2 DOUBLE STATOR SRM The components of the normal force that affect the performance of the linear SRMs are substantial. The DSSRM has enough ability to use appropriate radial force components in opposite direction in order to develop the motor performance to an acceptable level without experiencing any radial forces. The DSSRM structure composes of two opposing stators and a back-to-back rotor which is placed between the two stators. Structure of the rotor consists of either a yoke or discrete segments. Two opposite stators and the air gaps can create balanced radial force components on the rotor to produce high power density [14]. In DSSRM, the tangential force density related to the radial force is greater than the conventional SRM. It is worth mention that, the produced torque in this motor is directly dependent on the tangential force while the radial force does not help in torque production mechanism. The components of radial and tangential forces in segmented DSSRM are illustrated in Figure 1. Outer Stator Motion Direction FR-O FT-I FT-O FR-I Roto r Inner Stator Shaft Figure 1. The components of radial (FR-O-FR-I) and tangential (FT-O+FT-I) forces in segmented DSSRM. It is noted that, the radial force components of outer (FR-O) and inner (FR-I) stators in DSSRM structure are in the opposite directions. Whereas, the tangential force components of the both inner and outer stators are in the same direction. Therefore, they added up. 2098 Modeling and Simulation of a 16/12 Double Stator Switched Reluctance Motor In general, structure of DSSRM with approximate radial forces balanced will achieve a higher propulsion force, lower acoustic noise, and vibrations. Furthermore, the DSSRM with segmented rotor increases the torque per volume of the motor via decreasing the rotor weight. Therefore, the radial balanced forces and the segmented rotor of DSSRM are two key points which make the DSSRM as a suitable candidate for the most cost-effective alternative motors. In contrast, The DSSRM possesses some drawbacks. High torque density of the DSSRM also creates negative consequences. The high torque pulsation of the DSSRM is a negative point which caused by interaction between central rotor and changing reluctance of the two inner and outer stators. Furthermore, t (...truncated)