Effect of the Induction Motor Stator Outer/Inner Diameter Ratio on the Motor Performance Asım Gökhan Yetgin * , Ali İhsan Çanakoğlu + , Ayhan Gün + , Mustafa Turan # , Barış Cevher # * Mehmet Akif Ersoy University, Department of Electrical and Electronics Engineering, Burdur, Turkey agyetgin@mehmetakif.edu.tr + Dumlupınar University, Department of Electrical and Electronics Engineering, Kutahya, Turkey {aihsan.canakoglu, ayhan.gun}@dpu.edu.tr # Sakarya University, Department of Electrical and Electronics Engineering, Sakarya, Turkey {turan, bcevher}@sakarya.edu.tr Abstract— Induction motors are frequently used in industrial and domestic applications. For this reason, an improvement in performance values has a great saving in terms of energy savings. In order to be able to improve the performance values, it is necessary to be done with care from the beginning to the end of the design period of the motor. In recent years, a noticeable improvement in motor performance has been achieved, especially with the improvement of materials used in motors. In addition, performance enhancements are provided by using optimization methods for the parameters of stator and rotor slot dimensions. Also, stator winding structures have been changed to reduce the losses and increase the efficiency value. In this paper, the variation of the stator outer diameter value and the stator inner diameter value ratio (KD) obtained at the beginning of the induction motor design process was investigated. Although this ratio is not considered much during design, but it has a great influence on the motor volume. Other parameters of the motor were taken constant during analysis. The analyses were carried out on a 5.5 kW and 10 kW squirrel cage induction motor. According to the results obtained, decrease in the outer diameter of the stator was accompanied by increase of the KD ratio. The decrease in outer diameter resulted in a reduction in stator back iron height, resulting in an increase in the magnetic flux density values in the stator back iron parts. There was also a certain increase in the weight of the back iron with the increase of the outer diameter. In the case of stator back iron and iron losses, there is no visible change due to the increased value of the magnetic flux density and the decreased weight. The efficiency value also remains constant. Keywords— Induction motor, Stator outer diameter, Stator inner diameter, KD ratio, Performance analyses. I. INTRODUCTION Induction motors are widely used in domestic, commercial and various industrial applications. Mostly, the squirrel cage induction motor is used because of its simplicity, robustness and low cost, which has always made it very attractive, and it has therefore captured the leading place in industrial sectors. High efficiency motors lead to significant reductions in energy consumptions and also reduces the environmental impact. Sustainable use and investments also demands increased motor reliability. An important measure for wide market acceptance of high efficiency motors is availability of harmonized standards, dealing with motor performance testing, efficiency classification, and display of ratings [1]. The design of electrical machines involves several fields of physics, electromagnetism, thermic, mechanics, and acoustics. For a multiphysics model machines there are three approaches: the first is the analytical approaches: based on the analytical solution or equivalent circuit, quick and easy but the lowest in terms of accuracy. The second one is semi-analytical approach based on the nodal modeling or permeances network, the principle of nodal modeling method is to simplify the study of a system equivalent circuit. The most common formulation is one in which Kirchhoff’s current law is used to establish a system of nodal equations, the second method based on a decomposition of the magnetic field of the machine into elements. Permeances network less accurate and needs offline FEM results to evaluate the unknown air-gap permeances. The last one represents the state-of-the-art in the numerical magnetic field computation relating to electrical machines, FEM 2D or 3D is a numerical method to solve the partial differential equations (PDE) that expresses the physical quantities of interest. Give a more accurate result co analytical modeling, which can be regarded as a simplification of the PDE [2]. The selection of the frame size normally dictates the outer diameter of the stator laminations. Each manufacturer has standard lamination dimensions by frame size and poles. For a typical 4-pole motor, the stator inner diameter is approximately 2/3 that of the stator lamination outer diameter. The inner diameter of the rotor lamination may be affected by mechanical considerations, such as the need for a specific shaft diameter. After the initial lamination diameters are determined, the number of stator slots, the stator-rotor slot combination, and grade of electrical steel must be determined. These choices are influenced by the kW/HP rating, rpm, winding type, rotor construction, and performance criteria [3]. In this study, the ratio between stator inner diameter and stator outer diameter have been changed and it has been investigated that effect of this ratio on motor performance. By changing this ratio, the stator outer diameter values were changed and all the other parameters belonging to the motors were kept constant. Thus, only the effect of stator outer diameter on the motor performance has been investigated. 7th International Conference on Advanced Technologies (ICAT’18) April 28-May 1,2018,Antalya/TURKEY _________________________________________________________________________________________________________________ E-ISBN: 978-605-68537-1-5 241