Performance Evaluation of Different NEMA Induction Motor Designs under the Effect of Unbalanced Supply Voltages

Three-phase induction motors (IMs) are generally used in commercial, industrial, and domestic applications due to their advantages, such as good self-starting ability, simplicity, high reliability, cost-effectiveness, low maintenance, and ruggedness in construction. The IMs are exposed to different internal and external faults; one of the most popular external faults is unbalanced supply voltages. Unbalanced supply voltage is a popular and worldwide phenomenon that effectively decreases the characteristics of IMs. The present work shows the adverse effect of unbalanced supply voltages on the steady-state characteristics of all NEMA (National Electrical Manufacturers Association) designs of 20hp squirrel cage IMs (SCIMs). A symmetrical component is used to determine the performance of each NEMA design operating in different unbalanced supply voltage situations. The importance of this paper is that it likens different NEMA designs regarding torque-speed characteristics, efficiency, power factor, stator currents, rotor currents, torque pulsation, a ripple in rotor speed, and starting-up performances when subjected to over and under-unbalanced supply voltage conditions. Also, the MATLAB and Simulink environments have been utilized concurrently for simulation purposes.