taken, electric drives draw currents from the utility that are distorted (non‐sinusoidal) in their wave shape. This distortion in line currents interferes with the utility system, degrading its power quality by distorting the utility voltages. Available technical solutions make the drive interaction with the utility harmonious, even more so than line‐fed motors. The sensitivity of drives to power system disturbances such as sags swells and transient overvoltages should also be considered. Again, solutions are available to reduce or eliminate the effects of these disturbances.
1‐8 USE OF SIMULATION AND HARDWARE PROTOTYPING
Through the course of this book, modeling tools are used to facilitate discussion and provide in‐depth understanding of the concepts in electric drives. MATLAB/Simulink™ and Sciamble™ Workbench [5] are computer simulation tools used to demonstrate all topics in this course.
MATLAB/Simulink™ is widely accepted as the standard tool for electric drives simulation and analysis. The student version of this tool is sufficient for the purposes of this text and is reasonably priced for educational institutions. With an abundance of online training material, it is easy for a new user to become proficient in its use.
Sciamble™ Workbench is a mathematical simulation tool developed at the University of Minnesota for educational purposes. Workbench simulation software is free of cost enabling academic institutions access to advanced tools in education. All examples and key concepts explained in this book are also simulated using Workbench and the results are provided in the accompanying website.
Another noteworthy motivation for using Sciamble™ Workbench is its seamless transition between mathematical simulation and hardware prototyping modes. Hardware prototyping simplifies the development of a real‐time controller enabling rapid laboratory experimentation of concepts taught in this book. Real‐world experimentation enables a more in‐depth and practical understanding of the contents of this book. Sciamble™’s electric drives hardware kit is used for laboratory implementation of all topics in this book.
All the simulation files using both MATLAB/Simulink™ and Sciamble™ Workbench, as well as the manual for laboratory implementation using Workbench, are available on the accompanying website.
1‐9 STRUCTURE OF THE TEXTBOOK
This book is in three parts: Part I describes the fundamental concepts required for the study of ac electric machines and drives, Part II describes the steady‐state analysis of ac machines and drives, and Part III describes the dynamic analysis of ac drives and their vector control through simulations, leading to the hardware implementation of vector control. Throughout this book, the analysis leads to simulations using MATLAB/Simulink™ and Workbench of Sciamble™ (www.sciamble.com), a University of Minnesota startup. The simulations in Workbench of Sciamble™ seamlessly lead to hardware implementation, as described throughout the book. These are as follows:
1 Part I: Fundamental ConceptsChapter 2 deals with the modeling of mechanical systems coupled to electric drives, as well as how to determine drive specifications for various types of loads. Chapter 3 describes magnetic concepts and the laws governing electromechanical energy conversion. An introduction to PPUs is presented in Chapter 4. Chapter 5 explains the design of feedback control in vector control of ac drives. As a background to the discussion of ac motor drives, the rotating fields in ac machines are described in Chapter 6 utilizing space vectors. In controlling PPUs, the role of space vector PWM is described in Chapter 7.
2 Part II: Steady‐State AnalysisUsing the space vector theory, the sinusoidal PMAC motor drives are discussed in Chapter 8. Chapter 9 analyzes induction motors and focuses on their basic principles of operation in a steady state. A concise but comprehensive discussion of controlling speed with induction‐motor drives is provided in Chapter 10.
3 Part III: Dynamic AnalysisChapters 11 and 12 lay down the foundation on dq‐based analysis of ac machines and drives. Chapter 13 describes the vector‐control of induction motors. Chapter 14 is on encoder‐less vector control of induction motor drives. Chapter 15 is on doubly fed generators used in wind generators. Direct‐torque control is explained in Chapter 16. The vector control is applied to the surface permanent, and the interior permanent‐magnet motor drives in Chapter 17. The reluctance drives, including stepper‐motors and switched‐reluctance drives, are explained in Chapter 18.
1‐10 REVIEW QUESTIONS
1 1. What is an electric drive? Draw the block diagram and explain the roles of its various components.
2 2. What has been the traditional approach to controlling the flow rate in the process industry? What are the major disadvantages which can be overcome by using ASDs?
3 3. What are the factors responsible for the growth of the adjustable‐speed drive market?
4 4. How does an air conditioner work?
5 5. How does a heat pump work?
6 6. How do ASDs save energy in air conditioning and heat pump systems?
7 7. What is the role of ASDs in industrial systems?
8 8. There are proposals to store energy in flywheels for load leveling in utility systems. During the off‐peak period for energy demand at night, these flywheels are charged to high speeds. At peak periods during the day, this energy is supplied back to the utility. How would ASDs play a role in this scheme?
9 9. What is the role of electric drives in electric transportation systems of various types?
10 10. What are the different disciplines that make up the study and design of electric‐drive systems?
REFERENCES
1 1. https://eere‐exchange.energy.gov/FileContent.aspx?FileID=3b30e33e‐9f3e‐442b‐b623‐d724924b8581
2 2. https://www.eia.gov/tools/glossary/index.php?id=Primary%20energy
