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เนื้อหาย่อ : There is nothing sacred about a textbook. It is used only to assist the student in his acquisition of knowledge. The purpose of an engi- neering textbook is specific. It must serve as an agent by which the principles of engineering are imparted to the student. All these prin- ciples of engineering are not found in any one book. Many of the principles of engineering are characterized by their application to alter- nating-current machinery. The machines may not be important in themselves to the intellectual development of the student. However, the theories of the operation of these machines can serve as an excellent medium for the development of engineering disciplines. The material, the method of presentation, and the order of presentation incorporated in this revision are selected on the basis of effective training in these engineering disciplines. The form of the book has not been changed greatly by this revision. However, the approaches to the theories of some of the machines have been modified. Instructors acquainted with previous editions will note significant changes in the more detailed developments of equivalent circuits, vector diagrams, methods of calculating the cross-axis volt- ages of synchronous machines, and the equations describing the oscilla- tions of synchronous motors.Both the double-revolving field theory and the cross-feld theory have been retained for single-phase induction motors, and additional material has been added in the latter to clarify the polarities of the transformer and speed voltages. Additional material is provided on adjustable-speed drives, recti- fers, and self-synchronous machines. Methods of determining the constants of synchronous machines have been added. The nature of short-circuit currents in alternators has been explained on the basis of the constant fux-linkage concept. m greatly indebted to Professors Felix Zwieg and Peter M theiss of Yale University for their help and suggestions in this revision. am deeply appreciative of the patient and meticulous services of Mrs. Anne L. Kintner and Mrs. Jean Hartman, who did the typing. I am particularly fortunate in having taken my undergraduate and