Electric Power Principles, 2nd Edition

14Induction Machines

14.1 Introduction

Induction machines are perhaps the most widely used of all electric motors. They are generally simple to build, rugged, and offer reasonable asynchronous performance: a manageable torque–speed curve, stable operation under load, and generally satisfactory efficiency. Induction machines can also serve as generators. Induction machines, either wound rotor or squirrel cage, dominate as generators for wind turbine systems.

While induction motors have been around for quite a long time and are widespread in application, new uses for these machines are emerging: propulsion motors for transportation, high‐speed motors for turbocompressors, compact machines for auxiliary drives in aircraft, and others.

Because they are so widespread and applications continue to grow, a general knowledge of induction machines is important. Space does not permit a thorough explication of all aspects if induction motor analysis, however, but it is hoped that this chapter will serve as a good introduction to the topic.

Figure 14.1 shows one reason why induction motors have such widespread application. This figure shows the torque versus speed characteristic of an induction motor rated at 10 kW (about 15 hp), while the motor is connected to a 60 Hz, three‐phase voltage source. With the load torque shown, the motor can start itself and the load, that is, the motor produces torque that is greater than load torque from zero speed to an equilibrium speed, which is, for ...