Modern electric drives are used extensively in industrial applications to perform a mechanical maneuver for a given load. In addition, they have other widespread applications, ranging from robots to automobiles to aircraft. Recent advances in the design of electric drives have resulted in low-cost, lightweight, reliable motors. Moreover, advances in power electronics have resulted in a level of performance that was not possible a few years ago. For example, induction and synchronous motors were never used in variable-speed applications until variable frequency and rapid switching were developed. In addition, owing to advances in power electronics, several designs of electric motors are now available. This book "Electric Drives Principles" is designed to be used as a teaching textbook for two-semester courses on electric drives and variable speed drives. Readers are expected to be familiar with the basic electric machinery, power electronics and mechanics fundamentals. The material of this book divides itself into seven Chapters.