The aim of this book is to give an introduction to the theory of electromechanical devices, with specific emphasis on the theory of rotating electric machines. The basic concepts have remained more or less the same over the years since the first edition of this text appeared in 1985.

Since the appearance of the second edition in 1977, most of the advances in the application and control of electric machines have taken place owing to the further breakthroughs in power electron-ics and microprocessor/computer-based control systems. As a result, a much broader spectrum of electric machine types are now available. Particularly, permanent-magnet and variable-reluctance machines are now finding many applications that are bound to increase in future. AC drives are becoming more and more attractive in many applications, such as those requiring variable speed and flexible control while earlier dc machines were the only choice. Realising this fact, these machine types find in-creased coverage in the third edition.

Although much of the material from the previous editions has been retained in this edition, the following modifications/additions have been made.

• Chapter 1 has been updated with the recent findings in R&D in electric machines.
• New content pertaining to permanent-magnet materials and their application has been included in Chapter 2.
• New articles on voltage and current transformers, audio-frequency, and grounding transformer have been added in Chapter 3.
• In Chapter 6, steps for designing armature winding using MATLAB have been added.
• Due to increased importance of renewable energy sources and energy conservation, articles on induction generator and energy efficient induction motors find place in Chapter 9 along with two new articles on classes of squirrel cage motors and inverted induction machine.
• Chapter 11 is now better organized and includes all the latest devices along with vector (direct torque) control of an induction motor.
• A new appendix on resistance has been added.
• A new appendix on programs for solving examples using MATLAB has been added.

Though no sophisticated mathematics is required of the reader of this book, the mathematics at times can get messy and tedious. This is particularly true in the analysis of AC machines in which there is a significant amount of algebra involving complex numbers. One of the significant positive developments in the recent years is the widespread availability of software such as MATLAB which greatly facilitate the solution of such problems. MATLAB is freely used in many institutions and colleges and is also availa-ble in a student version (http://www.mathworks.com). This edi-tion, therefore, incorporates MATLAB in some sample solved exam-ples as well as in a few unsolved problems. It should be emphasized here that the use of MATLAB is not a prerequisite for using this book. It is just an enhancement, an important one though! Further, it may be noted that even in the cases where it is not specifically sug-gested, most of the problems in the book can be worked using MATLAB or an equivalent program. Some additional programs for solving problems using MATLAB are included in this book as an appendix. The help rendered by Dr. Mairaj Ud-Din Mufti of NIT, Srinagar and Ms. Parul Goyal, an M.Tech. student at IIT Delhi in writing these programs and solving problems using MATLAB is thankfully acknowledged.

Tata McGraw-Hill and the authors would like to thank the reviewers whose comments and suggestions played a valuable role in finalizing this edition.

While revising the text, we have been greatly encouraged by many colleagues, students and practicing engineers who used the earlier editions of this book. All these individuals have in-fluenced this edition. We express our thanks and appreciation to them. We hope this support/response would continue in the future also.

D P KOTHARI
I J NAGRATH