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- PLATE IV. Motor driven Interru t r p e . The Electro l tic Rectifier. PLATE V . y P LATE ” II . Trans ormer for 1 2 A a ratus f pp . ” 1 2 Coil . T H E T E S L A H I G H F R E Q U E N C Y C O I L I TS C O NS TR U C TI O N A ND US E S BY 0 , Q GEOR GE F F HALLER AND ELMER TILING CUNNINGHAM 56 ILLUS TRATIONS NE W Y O R K A R A D M P D . V N NO S T N C O A NY 2 M Y A D 0 2 ' 3 URRA N 19 1 7 WARREN Sr s . o ri ht 1 1 0 b C py g , 9 , y D AN N S N NY . V O TRA D COMPA ” i c . P 1 om ete 1 2 A aratus . F ront s ie e LATE . C pl pp p INTRODUCTION IN presenting this b ook on the Tesla coil to the public the authors hope that they have filled a long felt vacancy in the practical library of science . No attempt has been made to n give a mathematical explanatio of the oscillation transformer, a s h- and other p rt of the hig frequency apparatus, for the simple reason that the theory is too complex , and when obtained of no practical use . Neither have the authors tried to lead the amateur, who is just learning how to string bells and connect batteries , from the elements of the galvanic - cell up to the working of a high potential , alternating cur m ff rent, but have merely ade an e ort to place in the hands of advanced amateurs in electrical science a practical working - manual on the construction of high frequency coils , now so useful in scientific investigation . The attention of the authors was first called to the Tesla coil when they were fortunate enough to be given the use of “ ” 1 the 7 standard coil described in the last chapter of this on book . A systematic line of experiments was carried with V } efiec ts it, in order to study the of a change in the constants k 3of the various circuits . All the mechanical and electrical ‘ 3 5 details of construction were carefully worked out, and the authors finally decided to design and construct a larger coil . The coil, as first constructed, was a decided failure, due to vi Introduction too small a condenser capacity . For about five months they further experimented on the details of construction and ” 1 T finally arrived at the 2 coil described in this book . his emcient coil they feel assured is as as can be made . It is especially designed to give a high - frequency discharge of T k great volume . his latter fact ma es it useful for wireless telegraphy . 0 . In conclusion they have to thank Mr . G . Mitchell for many suggestions and for the kindly interest he has taken in T this work. hey feel that without his help the writing of this little book would have been impossible . CONTENTS CHAPTER I GENER SURVEY . AL II THE T NS F E . RA ORM R III THE N ENSE . CO D R IV THE OS N T NS F R E . CILLATIO RA O M R THE IN E U E V . T RR PT R VI THE NS U N OR THE XE S . CO TR CTIO BO VII ASSE N . MBLI G III THE Y THE Con. V . OR OF IX USE S THE Con. OF X D E NS NS OP ’ S N . IM IO 7 TA DARD COIL APPE NDIX LIST OF PLATES FACING PAGE ’ Complete 1 2 Apparatus F rontispiece ’ Transformer for 1 2 Apparatus ’ O sc illation T ransformer and Glass for Condenser of 1 2 Coil Motor-driven Inte rrupter The Elec t rolytic Rec tifier ’ Discharge from the 1 2 Coil ’ The 7 Standard Apparatus Li st of Figures High -tension B ushing O sc illators and Standards Wiring D iagram Waves on Wires ’ P rimary and Core of Transformer of 7 Coil ’ Secondary B ob b in of Transformer of 7 Coil Plate and Frame of Condense r ’ O sc illation T ransformer of 7 Apparatus ’ Box for 7 Apparatus W 1r1ug Diagram ” O sc illators and Standards for 7 Apparatus O sc illation T ransfo rmer of Small Coil Completed Transformer of Small Coil P rimary Spark-gap Wiring Diagram Wiring Diagram TH E TE S LA C O IL CHAPTER I GENERAL SURVEY BY far the largest and most interesting branch of science is electricity, for Maxwell has proven mathematically , and Hertz verified experimentally , that light is an electromagnetic to disturbance in the ether, and thus added that subject the realm of electricity . Amongst the various phenomena of - electricity, those of the high tension current are the most all interesting and instructive . With such a current the wonders of the Geissler and Crookes tubes may be seen . With it waves for wireless messages may be sent out into space , and a great number of other experiments carried out . It is the purpose of this book to S how how a satisfactory apparatus for producing these currents may be constructed, and also to describe a few of the uses for such a coil . The apparatus , as described in this book , is most commonly n T - C an in k own as the esla High Frequency oil , d consists , - h : I . Th T . T e general , of four parts e Step Up ransformer "2 Th . T Interrupter " 3 . e Condenser " 4 The Oscillation rans E of former . ach these will be fully considered in subsequent chapters . Before entering upon the description of the Tesla high u frequency apparat s , however, it would be well to make a few general remarks which are of the greatest importance . CHAPTER II THE TRANSFORMER THE transformer sometimes called a converter is ee an m r ly induction coil that. is connected directly to the - alternating current mains, without the use , of an interrupter, and is used to raise or lower the voltage . In a transformer the number of watts in the primary equals approximately r the number of watts in the seconda y . - u In the case of any step p transformer, the ratio of the number of volts in the primary to those set up in the sec ondary is nearly the same as the number of turns of wire in the primary to the number in the secondary " but the amperes decrease in the inverse ratio . The transformer used in the coil described in this book is m - - - of the com on induction coil type, oil immersed , step up transformer . It takes the alternating current from the mains 1 10 at volts or 55 volts , and steps it up to about volts . The efficient working of a transformer depends largely The upon the design of the core . iron used must be of high permeability and should have little retentivity . A straight core is always best to use "for, on the fall of the current from l its maximum value to zero , the magnetic flux fal s from its maximum value, not to zero , but to a value which depends 4 The Transformer 5 The on the residual magnetism . residual magnetism in an open circuit is much less than in a closed magnetic circuit, so that when the current suddenly becomes zero , the mag netic flux drops lower in an open circuit than in a closed one . As the electromotive force in the secondary is proportional to the fall in the magnetic field , it is greater with a straight of core than with a closed circuit iron . The coil designer is obliged to determine the length of the iron core from the experience of others , as the mathe r too matics fo calculating it is complex, although simple and useful in the case of closed circuit transformers . If the core is made too long the primary magnetizing current will be w too too large , hile if made short the secondary coils would of too to ffi T have to be made large a diameter be e cient . here is , therefore, a certain length which will give the best results . In the case of this transformer the length of the core was determined after having gained all possible information from certain eminent men who had made a life study of these of for matters "in fact, all the dimensions the transformer this special use were determined in this way . Th f 20 2 2 S . e iron core is made up of pieces o No . or B . ” 1 The to gauge iron wire 8 long . wire is first cut nearly of size with a pair pliers, and , when assembled , the ends of the bundle are sawed off square with a hack saw . An ordi ” of 1 8 nary piece iron pipe , a little less than long, and having an internal diameter slightly less than 2 is tightly filled s with these wires . When putting the wire in, stand the pipe on end on a smooth surface , and force in each wire until 6 The Tesl a coil it hits this surface . When the bundle is finished, the upper end is sawed off with a hack saw to exactly ' The tube containing the iron wires is now placed in a coke or coal fire and left there until the fire burns itself out, thus T insuring slow cooling .

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