Abstract: Energy saving has become one of the priorities of the technology directions and interests in all countries of the world. In this paper, the efficiency and losses of induction motors are thoroughly investigated. The main aim is to increase the efficiency of an induction motor by reducing the losses resulted when the motor load is operating below its nominal value depending on a newly proposed technique. This research work is based on a comprehensive analysis of the energy losses of induction motors. To achieve that, the losses of induction motors are expressed through the parameters of the equivalent circuit. It was proved that the average efficiency of an induction motor when controlled by the proposed law is higher than the efficiency of the same motor controlled by traditional law by about 5%.

Abstract: In this paper, a modular approach has been utilized for investigation of the dynamic behavior and analysis the transient cases for a three-phase induction motor. By using motors with various power ratings (low, medium, and high). Mathematical model has been utilized with Matlab/Simulink to investigate the behavior of induction motor in both transient and steady state. Motor variables, (e.g. voltage, current, flux, speed and torque versus time) were investigated. A q-d axis based model is proposed to analyze the transient performance of three-phase induction motor using stationary reference frame [11-16]. This model could also be used for a wide range of horse power needed in scientific research and numerical applications. We will considered as a model for the study and analysis under different operating conditions for a 5, 50, and 500 hp induction motors. The motor stator voltage, the stator and rotor currents, the developed torque and rotor speed were numerically calculated and plotted for normal operation, short circuit, and unbalanced voltage source for the induction motor.