?/ - 3 SYNCHRONOUS MOTORS McGraw-Hill BookCompaiy Electrical World The Engineering and Mining Journal Engineering Record Engineering News Railway Age Gazette American Machinist Signal Engineer American Engineer Electric Railway Journal Coal Age Metallurgical and Chemical Engineering Power SYNCHRONOUS MOTORS AND CONVERTERS THEORY AND METHODS OF CALCULATION AND TESTING BY ANDRE E. BLONDEL Graduate and Professor, National School of Bridges and High-ways of France; Member of the Legion of Honor of France ; Honorary Member of the American Institute of Electrical Engineers; Member of Numerous Scientific, Technical, and Engineering Societies in France and other European Countries TRANSLATED FROM THE FRENCH BY C. O. MAILLOUX, M.E., M.S. Consulting Electrical Engineer WITH ADDITIONAL CHAPTERS BY COMFORT A. ADAMS, S.B., E.E. Professor of Electrical Engineering in Harvard University McGRAW-HILL BOOK COMPANY 239 WEST 39TH STREET, NEW YORK 6 BOUVERIE STREET, LONDON, E. C. COPYRIGHT, 1913, BY THE McGRAW-HILL BOOK COMPANY TRANSLATOR'S PREFACE PROF. A. BLONDEL was the first writer to publish a systematic, comprehensive work on Synchronous Motors; and his book, although it has now been before the public several years, still remains the leading work on that important subject. Owing to the non-existence of an English edition, it is not, however, as well known and as much appreciated as it deserves to be, by English-speaking readers. The translation of this celebrated, one might almost say classical, work into English, was undertaken at the suggestion of teachers and others who were desirious of making more extensive use of the work than is possible if the French text alone is available. The author and the publisher both accepted 'the suggestion that the scope and the usefulness of the book might be increased mate- rially by including in it some reference to " Rotary Converters." Excellent material for this purpose was already available in the form of a paper presented by Prof. Blondel, at the Electrical Congress in Paris, in 1900. Two other papers presented by him at the Electrical Congress at St. Louis, in 1904, also were of sufficient interest in this connection to make their reproduction desirable. It was decided to separate the contents of the book into three distinct parts. Part 1, relating to Synchronous Motors, corresponds to the original French work on Synchronous Motors. The author himself corrected the French text, and he also supplemented it with much new matter while the translation was in process. The proofs of the English text were submitted to several persons who were well qualified to criticise the text and suggest improvements therein. The French text of Part I is also supplemented by an additional chapter contributed by Prof. C. A. Adams, of Harvard University. Part I may therefore be considered fairly well brought up to date. Part II, relating to Synchronous or Rotary Converters, is made up of old and new matter. The old matter (Chapters I and II), constitutes a translation of Prof. Blondel's Paris-Congress vi TRANSLATOR'S PREFACE paper of 1900. The new matter consists of three chapters by Prof. Blondel, and a chapter contributed by Prof. C. A. Adams. Part III contains the reprints of the two papers presented by Prof. Blondel at the St. Louis Electrical Congress in 1904, relating to the applica- tion of his " two-reaction " method to alternators. A very few modifications and additions have been made in the text by the translator. His own strong objections to the terms " wattless " and " watted " made him very willing to eliminate them; and the recent action of the Standards Committee of the American Institute of Electrical Engineers in sanctioning and recommending " reactive " and " active " as substitutes, furnished the incentive and the pretext for doing this, even after a considerable portion of the type had been set. This book will, therefore, be the first book in which " wattless " and " watted " are replaced by " reactive " and " active " respectively. The translator desires to express his gratitude and sincere thanks to all who have encouraged and assisted him in the preparation of this book for the press. Special acknowledgment should be made of the very valuable services rendered by Prof. C. A. Adams. He was the first to suggest the publication of this book, and he has made many excellent suggestions, besides contributing two new chapters, and also reading and correcting the proofs of the entire book. Special thanks are also due to Prof. E. J. Berg, of the Univer- sity of Illinois, for his very thorough reading of the proofs of Part I, and for very excellent suggestions for changes and additions made by him, some of which are incorported in notes inserted in the text, and identified by the initials " EJ.B." Thanks for reading the proofs of Part I, and making corrections or suggestions are due to the following: Prof. D. C. Jackson, of Massachusetts Institute of Technology; Profs. W. I. Slichter and Morton Arendt, of Columbia University; Prof. H. H. Norris, of Cornell University; Mr. A. L. Jones, of the General Electrical Company. Thanks are due to Mr. C. W. Stone, of the General Electric Com- pany, and Mr. W. S. Rugg, of the Westinghouse Electric and Manu- facturing Co., for the data relating to American Synchronous Motors, given in Appendix B ; and also to the Edison Illuminating Company of Detroit, Mich., and to Mr. A. A. Meyer of its engineering depart- ment, for the information relative to the practical use of synchronous condensers contained in Appendix C. TRANSLATOR'S PREFACE vii The Translator desires to make special acknowledgment of the great courtesy and kindness of the distinguished author, Prof. Andre Blondel himself. The preparation of this book for the press has been a labor of love which has occupied very pleasantly and profitably a portion of the leisure moments of the translator. He considers himself remunerated amply, for the work involved, by the great privilege which has been one of the perquisites incidental to the task, namely, that of closer personal contact and acquaintance with the author; and he is very glad to have had the opportunity, through this translation, to help make the work and the talents of the author better known, as they deserve to be; for, unquestionably, Prof. Blondel is one of the great productive workers of our time in pure and applied electrical science. His work, great as it is in itself, becomes really wonderful and phenomenal, when the circum- stances under which it has been done are realized and appeciated: Though handicapped most unfortunately, by protracted serious ill health and physical suffering, he has, nevertheless, kept well in the front rank with his more fortunate contemporaries and colleagues in the entire world; and he has achieved fame and renown by great mental powers, by wonderful originality and versatility, not only as a scientist, a teacher, and an author, but also as an inventor, an engineer, and an expert. The great respect which is inspired by the prodigious quantity and the superior quality of Prof. BlondePs work turn to absolute wonder and to profound admiration, before the wonderful activity and the untiring energy of his highly gifted, well-trained mind. No tribute of praise is too great for the work of this man, who is at the same time a genius and a hero, with an innate love of science and a devotion to scientific progress which uphold and uplift him, and urge him onward, quand m$me, in spite of ill-health and physical suffering, to new researches and new achievements. THE TRANSLATOR. NEW YORK, December, 1912. CONTENTS PAGE TRANSLATOR'S PREFACE v INTRODUCTION. xv PART I CHAPTER I. GENERAL PRINCIPLES or SYNCHRONOUS MOTORS. i Construction Experimental Properties Case of Equal Electro- motive Forces Case of Unequal Electromotive Forces Elementary Explanation of Polyphase Synchronous Motors Elementary Explana- tion of Single-Phase Synchronous Motors Equations of Synchronous Motors, Analytical Theory Case of Symmetrical Polyphase Motors Graphical Representation of Operative Conditions, Blakesley's Method Equation of the Synchronous Motor by the Method of Complex Variables Excitation of Synchronous Motors. CHAPTER II. DETAILED STUDY OF OPERATION WITH NORMAL LOAD 31 I. PRINCIPLES OF THE ELEMENTARY THEORY -- NOTATION PRINCIPLE OF BIPOLAR DIAGRAMS Bipolar Diagram of the First Kind Motor- Vector 2 taken as Fixed Axis Applications of the Diagram of the First Kind Line of Equal Power Occurring with Constant Excitation Lines of Equal Phase Limit-Circle of Current Algebraical Relations Deduced from the Diagram Numerical Example Diagram of the Second Kind. The Vec- tor of the Generator E.M.F., Ei, as a Fixed Axis Power- Values as Function of the Lag-Angle 6 Use of this Diagram for the Study of Different Loads Curves of Constant Electric Power of the Motor when the Generator has Constant Excitation Current-Limit Circle Lines of Equal Phase Numerical Example. CONTENTS PAGE II. OPERATION OF A MOTOR WITH CONSTANT EXCITATION, SUP- PLIED AT CONSTAT E.M.F 49 Maximum Power Means of Determining the Practical Stability of Synchronous Motors Variations of Stability with Operating Conditions Numerical Example. III. COMPARISON OF POSSIBLE OUTPUTS AT CONSTANT LOAD WITH VARIOUS EXCITATIONS. CONSTANT POTENTIAL SUPPLY 55 Existence of a Current-Minimum V-Curves Use of Diagram of the First Kind Predetermination of V-Curves Theoretical Form of V-Curves Curve of Reactive Current Expression for Reactive Current Comparison of Outputs which the Same Alternator Can Devel.op with the Same Terminal Voltage, when used either as a Generator or as a Motor. IV. INFLUENCE OF MOTORS ON THE GENERAL OPERATION OF AN A.C. ELECTRICAL DISTRIBUTION SYSTEM 64 Effect of Current of Synchronous Motors on Distribution Systems Compensation with Respect to the Line or Circuit First Numerical Example Second Numerical Example Economic Study of Compensa- tion for the Line of Means of Motors Running without Lgad Saving in Cost of Equipment Saving in Annual Operating Cost Numerical Example Table I, Saving in Cost of Equipment Table II, Saving in Operating Cost Table III, Numerical Example Economy of Compensa- tion for the Distributing System by Means of Synchronous Motors Running with Load Numerical Example Regulation of Distribution- Voltage Compensation with Respect to the Generators Numerical Example Comparison between Synchronous and Induction Motors Use of Synchronous Motors to Raise Power-factor in America. CHAPTER III. ADDITIONS TO THE THEORY. SECOND APPROX- IMATION 91 Imperfections of the Theory Variations of Reactance with Lag of Current and Saturation of Fields. Armature Reaction First Applica- tion of Corrected Diagram Determination of Reactive Current as a Function of the Excitation, with Constant Active Current Particular Case where the Permeability of the Field-Circuit is Constant and the Two Reaction-Coefficients are Equal Second Application. Operation with Constant Excitation, on Constant-Potential Supply System V-Curves Influence of Field-Saturation on Stability Influence of the Wave-Form of E.M.F. Simplified Diagrams. CONTENTS xi PAGE CHAPTER IV. OPERATION OF SYNCHRONOUS MOTORS. HUNT- ING 106 Starting by Direct Current Starting with Alternating Current by Polyphase Motors Synchronism Observations on the E.M.F. Induced in the Poles Accessory Starting Apparatus. Installation of Syn- chronous Motors Starting of Single-Phase Machines Theory of Initial Synchronizing Separate Excitation Field Due to a Commutated Cur- rent Oscillations of Synchronous Motors Short-Period Oscillations Damping of Oscillations Long-Period Oscillations. CHAPTER V. TESTS or SYNCHRONOUS MOTORS 132 Characteristic Curves Measurement of Efficiency Experimental Tests Advantages and Disadvantages of Synchronous Motors. CHAPTER VI. OTHER MOTORS OPERATING SYNCHRONOUSLY WITHOUT DIRECT-CURRENT EXCITATION 141 Reaction Synchronous Motors Synchronous Motor with Alternating Fields. CHAPTER VII. BIPOLAR DIAGRAM OF THE SECOND KIND IN AMPERE-TURNS 147 Introduction Diagram Transformations E.M.F. Diagram Approxi- mate Diagram Extreme Cases Mechanical Analogue Length of Air-Gap. CHAPTER VIII. GENERALIZATION OF DIAGRAM FOR COUPLED SYNCHRONOUS MACHINES .. 166 PART II CHAPTER I. GENERAL DIAGRAMS DEDUCED FROM THE DIAGRAM FOR SYNCHRONOUS MOTORS 172 Introduction Notation Generalities. Reduction of all Armature Reactions to the Single Direct Reaction Factors Determining the Practical Conditions of Operators. xii ' CONTENTS PAGE I. CONDITIONS OF ELECTRIC-CURRENT SUPPLY TO ROTARY CONVERTERS 177 Fundamental Diagram Fundamental Equation Application of the Diagram. Representation of Converter Operation with Constant Potential at Primary Terminals and at Brushes General Case. Reactive Current Values for a Given Vdltage Variation as a Function of the Load Most Suitable Value of Current-Supply Voltage Most Suitable Value of Reactance Regulation of Voltage at Terminals by Variation of the Supply E.M.F. Regulation of Voltage at Terminals by Variation of Reactance Power-Factor of the Generator. CHAPTER IT. PREDETERMINATION OF THE FIELD EXCITATION OF ROTARY CONVERTERS 194 Characteristic Features of the Rotary Converter Compound- Excitation. Different Factors of this Excitation Determination of Reactive Current as a Function of the Excitation when the Active Current is Constant, then when the Power is Constant, the Generator E.M.F. being always Constant Different Values of the Excitation, with Con- stant Power and Constant Potential. V-Curves for Constant Potential Upper Limit of Reactive Current Lag-Characteristics of Rotary Con- verters at Constant Potential Effective Characteristic of Rotary Con- verter under Load Application in the Case of Separate Excitation Application to the General Case of Self-Excitation Regulation of Supply E.M.F. by Compounding of the Generator Regulation of Voltage by Varying the Reactance X in the Circuit Possibility of Suppressing the Shunt-Winding Conclusion. CHAPTER III. STABILITY OF OPERATION OF ROTARY CON- VERTERS 213 CHAPTER IV. OPERATION OF SEVERAL ROTARY CONVERTERS IN PARALLEL 219 Inherent Oscillations or Pumping of Converters Connected in Parallel Use of Rotary Converters for Transforming Direct into Alternating Current Other Special Applications of Converters Phase-Converters. CHAPTER V. VOLTAGE RATIO IN SYNCHRONOUS CONVERTERS WITH SPECIAL REFERENCE TO THE SPLIT-POLE CON- VERTER 225 CONTENTS xiil PART HI PAGE CHAPTER I. METHODS or CALCULATION OF THE ARMATURE REACTIONS (DIRECT AND TRANSVERSE) OF ALTER- NATORS 236 Principles of the Theory of Two Reactions Diagram of E.M.F.'s and Current of an Alternator with Unsaturated Armature and with Saturated Field Magnet Diagram of Ampere-Turns in the Case of Unsaturated Armature Remark No. i, Upon the Case of an Unsaturated Arma- ture Remark No. 2, Upon the Subject of Diagram No. i The Case of a Saturated Armature Local Corrections of the Air-Gap Due to Saturation (Second Approximation) Case of Field Magnets with Divided Windings Practical Calculation of Reactions Comparison with Theoretical Coefficients Case of Single-Phase Alternators Consequences from the Point of View of the Construction of Alter- nators for Good Regulation. CHAPTER II. METHODS OF TESTING ALTERNATORS ACCORDING TO THE THEORY OF TWO REACTIONS 270 Method No. i. When the Rigid Coupling of the Two Alternators is possible Method No. 2. Applicable to a Single Synchronous Machine Operating upon an Actual Conducting System Analogies between this Method and that of Potier Behrend Method No. 3 For the Determina- tion of Transverse Reaction (Coefficient L). APPENDIX A 283 APPENDIX B 285 APPENDIX C 287 INDEX 291