This fourth edition is again intended primarily for nonspecialist users or students of electric motors and drives. From the outset the aim has been to bridge the gap between specialist textbooks (which are pitched at a level which is too academic for the average user) and the more prosaic handbooks which are full of detailed information but provide little opportunity for the development of any real insight.
We intend to continue what has been a successful formula by providing the reader with an understanding of how each motor and drive system works, in the belief that it is only by knowing what should happen (and why) that informed judgements and sound comparisons can be made.
The fact that the book now has joint authors resulted directly from the publisher’s successful reviewing process, which canvassed expert opinions about a prospective fourth edition. It identified several new topics needed to bring the work up to date, but these areas were not ones that the original author (AH) was equipped to address, having long since retired. Fortunately, one of the reviewers (WD) turned out to be a willing co-author: he is not only an industrialist (and author) with vast experience in the field, but, at least as importantly, shares the philosophy that guided the first three versions. We enjoy collaborating and hope and believe that our synergy will prove of benefit to our readers.
Given that the book is aimed at readers from a range of disciplines, sections of the book are of necessity devoted to introductory material. The first two chapters therefore provide a gentle introduction to electromagnetic energy conversion and power electronics. Many of the basic ideas introduced here crop up frequently throughout the book (and indeed are deliberately repeated to emphasize their importance), so unless the reader is already well versed in the fundamentals it would be wise to absorb the first two chapters before tackling the later material. At various points later in the book we include more tutorial material, e.g. in Chapter 7 where we prepare the ground for unraveling the mysteries of field-oriented control. A grasp of basic closed-loop principles is also required in order to understand the operation of the various drives, so further introductory material is included in Appendix 1.
The book covers all of the most important types of motor and drive, including conventional and brushless d.c., induction motor, synchronous motors of all types, switched reluctance, and stepping motors (but not highly customized or application- specific systems, e.g. digital hard disk drives). The induction motor and induction motor drives are given most weight, reflecting their dominant market position in terms of numbers. Conventional d.c. machines are deliberately introduced early on, despite their declining importance: this is partly because understanding is relatively easy, but primarily because the fundamental principles that emerge carry forward to other motors. Similarly, d.c. drives are tackled first, because experience shows that readers who manage to grasp the principles of the d.c. drive will find this knowhow invaluable in dealing with other more challenging types.