G. Rizzoni, Principles and Applications of Electrical Engineering
Problem solutions, Chapter 18
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Chapter 18 Instructor Notes
The content of Chapter 18 is somewhat unusual for a textbook of this nature.
The intent of this
chapter is to provide a reasonably quantitative overview of the operation of small electric machines (mostly
motors).
In many practical industrial applications, ranging from servos for robots, to drug delivery
systems, to actuation devices for control systems, to manufacturing equipment, to fluid power systems,
small motors find widespread application.
The first section discusses the brushless DC motor, including the basics of the electronic circuits
that make its operation possible.
The second section introduces the stepper motor and its drive.
In section
18.3, the switched reluctance machine is introduced; this is a new section in the third edition, motivated by
the increasing interest in this family of machines for industrial applications.
Next, single phase AC motors
are discussed in Section 18.4, starting with the universal motor, and continuing with a classification of
single phase induction motors, which includes split-phase, capacitor-type and shaded-pole motors.
The
presentation detail is sufficient to permit quantitative analysis of these motors using circuit models.
The
final section, 18.5, on motor selection and application, introduces some of the basic ideas behind motor
selection and performance calculations.
This section, which describes calculations related to reflected load
inertias in the presence of mechanical gear reductions, and calculations of acceleration, torque, efficiency,
and thermal loading, could be covered at any point in Chapter 17 or 18, even if the material in Sections
18.1-18.4 is not covered.
The examples given in the chapter are supplemented by over thirty homework problems, some of
which are extensions of the examples presented in the text.
Problems 18.5 and 18.9 require some
background in digital logic circuits (Chapter 13); problems 18.7, 18.36 and 18.37 require some background
in system dynamics; all remaining problems can be solved strictly on the basis of the material covered in
the chapter.
Learning Objectives
1.
Understand the basic principles of operation of brushless DC motors, and the trade-offs
between these and brush-type DC motors. Section 1.
2.
Understand the operation and basic configurations of step motors, and understand step
sequences for the different classes of step motors.
Section 2
.
3.
Understand the operating principles of switched-reluctance machines.
Section 3
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4.
Classify and analyze single-phase AC motors, including the universal motor and various
types of single-phase induction motors, using simple circuit models.
Section 4
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5.
Outline the selection process for an electric machine given an application; perform
calculations related to load inertia, acceleration, efficiency, and thermal characteristics.