ISSN (Print) : 2320 – 3765 ISSN (Online): 2278 – 8875 International Journal of Advanced Research in Electrical, Electronics and Instrumentation Engineering (An ISO 3297: 2007 Certified Organization) Vol. 2, Special Issue 1, December 2013 Copyright to IJAREEIE www.ijareeie.com 374 Efficiency Optimization with Improved Transient Performance of Indirect Vector Controlled Induction Motor Drive Seena Thomas 1 , Rinu Alice Koshy 2 M.Tech Student, Rajagiri College of Engineering and Technology, Kakkanad, India 1 Assistant Professor, Rajagiri College of Engineering and Technology, Kakkanad, India 2 Abstract: This paper introduces an energy efficient induction motor drive suitable to operate at light load conditions. The iron losses in the induction motor are significant when the machine is operated below the rated conditions. The efficiency of the motor can be increased by keeping the flux level below the rated value. In this paper, the efficiency of the induction motor has been improved by incorporating an efficiency optimization algorithm. Efficiency optimization algorithm provides an optimum value of flux generating direct axis stator current, which controls the magnitude of the rotor flux. At light loads, the optimization algorithm weakens the rotor flux from its rated value, thus reducing the core losses. A 5.4-hp induction motor drive is simulated in SIMULINK to analyze the efficiency under different operating conditions of the drive. The variation of efficiency under load change and speed change is observed. Simulation results show that efficiency increases as the operation of induction motor drive shifts from unrated to rated conditions. The implemented algorithm is tested under different operating conditions of IM Drive including sudden change in load and reference speed. This paper also considers the transient performance of the drive with efficiency optimization algorithm. Keywords: Vector control, Optimization, Indirect field oriented control, Simulink I. INTRODUCTION It is estimated that electric machines consume more than 50% of the world electric energy generated. Economic saving and reduction of environmental pollution are the two factors that highlight the importance of analyzing the efficiency in electric drives. The induction motors are widely used in the electrical drives and are responsible for most of the energy consumed by electric motors [1]. In recent years the control of high-performance induction motor drives for general industry applications and production automation has received widespread research interests [2]. Many schemes have been proposed for the control of induction motor drives, among which the field oriented control, or vector control, has been accepted as one of the most effective methods [3]. Vector control offers a number of benefits including speed control over a wide range, precise speed regulation, fast dynamic response, and operation above base speed [4]. Induction motor operating at rated conditions is a high efficiency electrical machine. However, at light loads, IM drive shows considerable reduction in the efficiency. It is possible to obtain an optimum value of efficiency for any load condition with the introduction of efficiency optimization algorithm in the control technique of the induction motor [5]. Efficiency optimization is relevant in applications where the load torque is not constant and may vary from full load to light load conditions. Optimization can conserve energy by minimizing the iron losses in the machine. For industrial applications such as electrical vehicles, high efficiency is essential to extend the running distance per battery charge under all operating conditions [6]. Efficiency optimization is particularly applicable in marine vehicles where the light running conditions persist for long period of time. The focus of this paper is to obtain optimum efficiency for an induction motor (IM) drive especially at light loads, by minimizing the core losses which are considerable at these load conditions. This paper analyzes the performance of an induction motor drive with the implementation of efficiency optimization algorithm for different operating conditions. Simulation study of the proposed optimization algorithm is done in MATLAB/Simulink environment. The efficiency measurement for the induction motor drive will be carried out with and without efficiency optimization control at different speed and load conditions.