Introduction

Three-phase induction motors are by far the most widely used motors in industry, accounting for about 80% of the total number of motors used in the average plant. In many small and medium-sized industries, all motors above 3 kW are three-phase induction motors. Three-phase induction motors are popular because they are more economical, last longer, and require less maintenance than other types of motors.

Because of their importance, this chapter provides a detailed analysis of three-phase motors and a thorough discussion of their applications. The following subjects are discussed: principles of operation, rotating magnetic fields, equivalent circuits, governing mathematical relationships, industrial considerations, induction generators, and solid-state control.