TABLE OF CONTENTS Developed in this section are models useful for simulating operation of induction machines. These models are similar to those used for synchronous machines, and in fact are somewhat easier to handle analytically.
Among the more useful impacts of modern power electronics and control, technology has made it possible to turn induction machines into high performance servomotors. A picture of how this is done is shown in this section. The objective is to emulate the performance of a dc machine, in which torque is a simple function of applied current. For a machine with one field winding, this is simply
This makes control of such a machine quite easy, for once the desired torque is known, it is easy to translate that torque command into a current and the motor does the rest.
Dc (commutator) machines are, at least in large sizes, expensive, not particularly efficient, have relatively high maintenance require- ments because of the sliding brush/commutator interface, provide environmental problems because of sparking and carbon dust and are environmentally sensitive. The induction motor is simpler and more rugged. Until fairly recently, the induction motor has not been widely used in servo applications because it was though to be "hard to control." It takes a little effort and even some computation to correctly do the controls, but this is becoming increasingly affordable.
In an elementary model of the induction motor, in ordinary variables, referred to the stator, the machine is...
