Understanding of induction motors made easy

Complex motor theories and constructions make understanding electric motors and their applications difficult, especially induction motors where the actual motor speed is not the same as the electrical frequency of the power supply. Why does the current vary inversely with the voltage when the motor is running, but vary proportionally with the voltage when the motor is starting? In addition, when there is a small unbalance in the voltage supply, the motor temperature rise increases rapidly. What is behind this phenomenon? Some motors are designed with wye connection and some are designed with delta connection. What is the difference between these designs? All the above questions are interesting and confusing and the answers can be confusing as well. This paper's purpose is to provide readers simple steps to analyze and answer these questions. First, the motor parameters will be visually linked to the motor components; second, the motor equivalent circuit is analyzed to answer these difficult questions. The intent of this paper is that through these analyses, readers would gain a simple, yet insightful understanding of induction motors, their parameters and applications.