Furthermore, one cannot assume that any large technical subject over becomes a closed book and ceases to develop. On the contrary, developments in various allied fields usually provide new techniques which have applications to the subject considered, and it is necessary to revise the texts to pick up these developments from time to time. All will recognize the obsolescence of a book on electrical measurements published a decade or so ago. Older books on a-c. machinery, for example, do not specifically discuss selsyn devices, servomotors and numerous new applications of a-c. machine principles.
The teaching level of this book is appropriate for the sophomore year of the undergraduate E.E. course. The mathematics used in the analyses involves vector diagrams, algebra of complex quantities and elementary calculus. Material on transformers, and every practical type of a-c. motor is clearly presented with worked-out numerical illustrations. Each chapter is accompanied by a group of problems in which an attempt has been made to include some aspects of engineering as well as theory. Owing to the inclusion of a large amount of detail pertaining to the construction, design principles and performance of machines the studems of this book should derive considerable useful knowledge of a-c. equipment. Sufficient diagrams and curves are used so that the student will learn how to make a creditable presentation of an engineering problem upon which he might be asked to report in a professional capacity.
When a professor of electrical engineering has taught a subject for many years, as have the authors of this book, it is to be expected that his own nnderstanding of its ramifications will become more thorough and his explanations more lucid. The teaching experience of the authors has supplied the wisdom for choosing the material for a first course in a-c. machinery. The volume appears to be up-to-date as well as basically sound. It should be a pleasure to use this book for the instruction purposes for which it is intended although there will perhaps be little demand by those desiring a complete reference on the engineering aspects of a-c. machinery.