International Journal of Computer Applications (0975 – 8887) Volume 62– No.12, January 2013 40 Optimal Efficiency Controller of AC Drive System Rateb H. Issa Mechatronics Engineering Department Faculty of Engineering Technology Al- Balqa Applied University ABSTRACT This paper has presented a mathematical-based scheme for induction motor drive system leading to efficiency optimization. The proposed scheme uses information on torque of the squirrel cage motor to generate the appropriate voltage amplitude that maximizes the motor efficiency. A constantV/f efficiency controller model has been configured and built depending on a set of experimental data, based on the motor equivalent circuit, using Matlab computer program. The model was validated by simulation using a typical induction motor drive model implemented with Matlab/Simulink. The aim of this paper is the drive system performance improvement by designing optimal efficiency controller; this will supply stator of the motor with proper voltage and frequency under different loading conditions using appropriate algorithm. General Terms Algorithms, Performance, Experimentation. Keywords Squirrel CageMotor, Efficiency, Drive System, Optimization, Modeling, Simulation. 1. INTRODUCTION The importance of energy saving techniques implementation in industry can be pointed out from two points of view: 1- It is well known that more than 60 % of total generated electrical energy is consumed by electric motors in industry. Therefore, motor energy saving solutions by increasing its efficiency has received considerable attention during the last three decades due to the increase in energy cost [1] & [2]. 2- Three-phase asynchronous motors, especially the squirrel cage type are widely used in industrial electric drives and are responsible for most of energy consumed by electric motors in industry [3]& [4]. Energy saving can be achieved by following means of electric drive system loss reduction: A- Electric motor selection and design. B- Improvement of power supply parameters. C- Utilizing a suitable optimal control technique. Motor operation under rated conditions is highly efficient [5], however, in many applications, when induction motor works at variable speed it has more losses and less efficiency, so it operates far from the rated point[6]. Under these circumstances, it is not possible to improve the motor efficiency by motor design or by supply waveform shaping technique. Therefore, a suitable control algorithm that minimizes the motor losses will rather take place [7]-[9]. The need of efficient drive system could be achieved by special controllers that not only modify the losses and efficiency, but also searching for the optimal efficiency to reduce the power consumption from the source [10]-[13]. In this paper will be designed an optimal efficiency Controller, which will minimize the motor losses under different loading conditions, by varying stator voltage and frequency as a function of motor load torque, depending on industrial machinery type. 2. AC Drive System Components The block diagram of voltage source inverter-three-phase squirrel cage induction motor drive system is presented in Figure 1. It consists of three-phase squirrel cage induction motor, IGBT-voltage source inverter-based AC-to-AC converter, and optimal controller [10]. In order to analyze the system performance, all of these components should be modeled [14] & [15]. Fig 1: Block diagram of an inverter-three-phase squirrel cage induction motor drive system 2.1 Squirrel Cage Induction Motor AC drive systems are used worldwide in many residential, commercial, industrial, and utility applications. Electric motors transform electrical energy into mechanical energy. An AC motor may be part of pump or fan, or connected to some other form of mechanical equipment such as a winder, conveyor, or mixer. 2.1.1 Per-Phase Equivalent Circuit of Induction Motor Theper-phaseequivalent circuit of induction motor is shown on figure 2 [16]. Where: 1 R : Stator resistance. R \ 2 : Rotor resistance referred to stator circuit.