Armature Winding and Motor Repair , livre ebook

ARMATURE WINDING AND MOTOR REPAIR
Practical Information and Data Covering Winding and Reconnecting Procedure for Direct and Alternating Current Machines, Compiled for Electrical Men Responsible for the Operation and Repair of Motors and Generators in Industrial Plants and for Repairmen and Armature Winders in Electrical Repair Shops


BY
DANIEL H. BRAYMER, A. B., E. E.
MEMBER AMERICAN INSTITUTE OF ELECTRICAL ENGINEERS-MANAGING EDITOR OF ELECTRICAL WORLD-FORMERLY EDITOR OF ELECTRICAL ENGINEERING AND OF ELECTRICAL RECORD


F IRST E DITION T WENTY-SEVENTH I MPRESSION


M C GRAW-HILL BOOK COMPANY, I NC . NEW YORK AND LONDON
PRINTED IN THE UNITED STATES OF AMERICA





THE MAPLE PRESS - YORK PA
PREFACE
In this book no attempt has been made to discuss the subject of armature winding from theoretical or design standpoints. On the contrary, it is a compilation of practical methods that arc used by repairmen and armature winders. In selecting the material a special effort has been made to include as far as possible details of those methods which have been found by actual experience to represent best practice in a repair shop of average size. In this work the writer has drawn from his own experience in repair work, from the experiences of repairmen and armature winders in large and small repair shops and manufacturing plants which have been visited, from descriptions of practical methods and the procedure followed in the solution of special problems as presented by practical men in technical journals.
The title of repairman as used throughout this book is one that a good engineer can bear with pride when he measures up to all its qualifications. Such an engineer is one who in in the majority of cases not only knows what to do in the case of an electrical trouble but just how to proceed to do that particular thing and who seldom guesses without a good percentage of the probabilities of being right in his favor. The main difference between the designer and the repairman is that the former must know what to do while the latter must know how to do it. A capable repairman combines both qualifications through years of experience.
When called upon to locate troubles in motors and generators, electricians and repairmen whose experience in this kind of work has been limited often find themselves wondering just what to do first. It is from just this viewpoint that the information on winding procedure and the hunting and correcting of troubles has been presented. That is, instead of discussing the fundamentals involved in any method of working out a repair problem, the actual problem or job as the case may be is discussed from the how-to-do-it standpoint. Then for each individual operation or procedure the applications of fundamental laws and rules are worked out, Considerable repetition of some details of similar methods will therefore be discovered in connection with information covering such procedure as the rewinding of machines of the same class but of different types. This has been considered advisable since a repairman should not be required to study a complete volume when details and information are desired at any one time on the procedure for a particular type of winding for a particular design of machine.
Liberal use has been made of practical data and practices in repair shops so as to combine the good features of a book of methods with handbook information covering these methods. If this book shall help young repairmen to absorb information that can be secured otherwise only through years of experience in handling one job after another, and if the older and more experienced repairmen find it a handy source of reference as a supplement to their own stock of information, then the aim of the author will be accomplished.
When material has been taken from the experiences of engineers and their recommendations on repair methods as published in the technical journals, it has been the aim to give credit to both the author and the journal in the paragraph, or section where the material is used. Special acknowledgment is made to A. H. McIntire, editor of the Electric Journal , for permission to make liberal use of information contained in several articles compiled at his suggestion and published in the Journal. This material has been incorporated in Chapters 3 , 8 , 9 and 11 . To A. M. Dudley, engineer of the industrial division, Westinghouse Electric Manufacturing Company, the author is also especially grateful for suggestions and for permission to use details of methods which he has developed for reconnecting and testing induction motor windings. This information appears in Chapters 9 and 11 . The diagrams at the end of Chapter 11 have been selected from a series of eighty-one devised by Mr. Dudley and shortly to be published in a valuable treatise on Connecting Induction Motors.
The author also desires to acknowledge the assistance rendered by H. S. Rich and Alex R. Knapp in the form of data and information compiled from their own experiences in solving a variety of motor troubles met with in industrial plants and in making repairs. To Henry Scheril, formerly a member of the engineering department of the Crocker-Wheeler Company, acknowledgment is made for helpful suggestions in arranging the material and for assistance in checking and reading the proof. Credit is also due and is hereby accorded to the electrical manufacturers who furnished the photographs from which many of the halftone illustrations were made.
D ANIEL H. B RAYMER .
N EW Y ORK C ITY , December , 1919.
INTRODUCTION
Through the courtesy of the author of this book the writer has had the privilege of reading the proofs. I have found, with great delight, that the treatment of the subjects discussed is not only clear and easily understood but always from the practical man s standpoint. While the book will appeal strongly to practical men engaged in repair shop work, power station work and the maintenance of motors in industrial plants, it will also appeal, in the opinion of the writer, to students of electricity. Since the material presented in this book, which I dare say is unique in its field, has been obtained from actual practical experiences and outlines the practical remedies that have been applied by repairmen in the solving of puzzling problems, it will be of decided assistance to men who are in need of such practical help.
It is an electrical book of knowledge, for in its pages readers will find answers to practically all armature winding questions and solutions of many of the repair problems that they will meet in practical work. The diagrams are clear and easily followed by the shop man and run in synchronism with the text. Theory with mathematical considerations have been resorted to only in a very few cases so that the reader of the book can make use of the information and understand the discussions of all phases of armature winding even though he may have only a limited knowledge of mathematics.
A book of this kind, in spite of the errors that are bound to creep in, is a very valuable asset to any practical man who desires to enlarge his own stock of knowledge by learning how other men in similar positions have solved the many electrical problems that come to the repairman.
H ENRY S CHERIL .
N EW Y ORK C ITY , December , 1919.
CONTENTS
P REFACE
I NTRODUCTION
CHAPTER I
D IRECT-CURRENT W INDINGS
Action of a Commutator
Types of D-C Armature Windings
Winding Parts and Terms
Armature Conductor or Inductor
Winding Element or Section
Armature Coils
Winding Pitch or Coil Pitch
Front and Back Pitch
Full Pitch and Fractional Pitch Coils
Symbols Used in Winding Formulas
Numbering Coil Sides in Armature Slots
Lap-Multiple or Parallel Windings
Formulas for Lap Windings - Multiple; Single, Double and Triple Windings - Meaning of the Term Reentrant - Multiplex Lap Windings
Wave-Series or Two-circuit Windings
Formulas for Wave Windings - Multiplex Wave or Series-Parallel Windings - Formulas for Series-Parallel Windings - Symmetrical Windings
Possible Symmetrical Windings for D-C Machines of Different Numbers of Poles
Equipotential Connectors
Best D-C Windings for a Repair Shop to Use
Number of Armature Slots
Voltage between Commutator Segments
Number of Commutator Bars
Usual Speeds and Poles of Different Sizes of Generators
Safe Armature Speeds
CHAPTER II
A LTERNATING -C URRENT W INDINGS
Types of A-C Windings
Distributed Windings
Concentrated Windings
Spiral or Chain Windings
Lap and Wave Windings
Whole-coiled and Half-coiled Windings
Single-phase and Polyphase Windings
Coil Pitch
Phase Spread of Winding
Two-phase from Four-phase Windings
Three-phase from Six-phase Windings
Wire, Strap and Bar Wound Coils
Methods of Laying out and Connecting A-C Windings
Group Windings - Full and Fractional Pitch Windings - Simple Winding Diagram - Reconnecting a Winding - Simple Method for Indicating Polarity of Coil Groups - Changing Star to Delta Connection - A-C Wave Windings - Progressive and Retrogressive A-C Wave Windings - Connections for Coils of Polyphase Windings - Double-layer Winding, Lap Connected - Connecting a Chain Winding - Other Common Windings
Easily Remembered Rules for Arrangement of Coils in an Induction Motor
Simple Rules for Checking Proper Phase Relationship in Two-or Three-phase Windings
CHAPTER III
R EPAIR S HOP M ETHODS FOR R EWINDING D-C A RMATURES
Dismantling a D-C Armature
Winding Data Needed for a Dismantled Armature
Removing Old Coils
Winding D-C Armatures Having Partially Closed Slots
Winding a Threaded-in Coil - Insulating Lining for Slots - Inserting Coils in the Slots - Insulating Overlapping End Connections of Coils - Connecting Finish Ends of Coils to Commutator - Loop Windings for Small Motors
Winding D-C Armatures Having Open Slots
Winding and Insulating Coils - Insulating Open Slots - Inserting Coils