Book: The Electrical Review
|Fib. 4.—"Sons Bxfxbountb in Tesla’* Ьавокатожт with Ovekknis of Ніан Pot ini ial and Шеи FaiquMCX."|
The operator's body, in this experiment, U charged to a high potential by means of a ooil responsivo to the waves transmitted to it from a distant oscillator, Mid a long glass tnbe waved in the band is lighted to great brilliancy by the electrical charges conveyed to it through the body.
prosare than the boiler pressure. Two tigp valves are ocopled to the cylinders from the duplicate main range. The normal load of the engine is 2,50Q I.H.P.| but it is capable
|!Tesla's High Potential and Hioh FriquinctWqak.—Fie. 1.|
of giving oat folly 26 per cent, above this load. A heavy
fly-wheel is keyed to tne crankshaft, and the wheel boss is also prepared to fasten to the dynamo. The sides of the engine are entirely enclosed, and forced lubrication is adopted. Two ram pampe are fixed on this engine far this purpose, and pomp (he oil under preesure (which can, Ъэ regulated at wiif) to the main bearings under and over, also to the crank pine, cross-head pins and slide blocks. A gauge is fixed in the pipes showing the pressure of oil supplied. The engines are
3 massive in appearanoe, and work noiselessly, no vibration is discernible. The moving partì of the engines are balanced in the cranks.
White anti-friction metal Ів need in all the bear ioga. The engine is also supplied with a
large platform snrronnding both cylinders, and an intermediate platform to enable the attendant to get at the cross-head, elides, and indicating apparatus.
The engine is made to work condensing and non-condensing, the oondenser being on Kort-ing’e principle, and Ів supplied by .water from a large tank over the boiler house.
The generator has been made by the Electric Construction Company,, Limited. The normal output is 3,500 amperes at 410 volts, the range of voltage extending to 430 with 4,750 amperes as an emergency load, or with normal oatput up to 500 volts when required for tramway work. The Bomewhat high speed of revolution had the effect of limiting the number of poles, which was fixed at 12, eaoh of which is energised by a double-coned shunt coil. The yoke frame, on aocoont of its magnitude, and to facilitate erection and accessibility, is divided into six puts, and measures overall 20 feet 6 inches. The total weight of the machine is, approximately 120 tons. The armature core is carried by a balanoed centre, provided with .a double set of arms of oval section. The armature is tunnel wound, and the coils are formed in one piece, i.e., without joint between one commutator segment and another,' the commutator iteelf being 9 feet lb inches in diameter. The brush gear includes an endless rack operated by 'worm gear and doable hand wheels, so that when standing on tne brush platform the attendant may replace old bmshss by having the. whole of the brash holders successively rotated past him. The current is taken off to the main terminals from the oircular positive and negative brash bos bars by special terminal brushes, the current bring too large ttì permit the ose of flexible leads. Notwithstanding the magnitude of the machine, the number of parte involved and the difficulty of erection, it was started under load witbont incident, and was at once pnt on to Corporation supply mains, and has been in use almost duly from the end of December until recently, when the exigencies of the load no longer demanded it. The electrical effioienoy of the set is over 98 per cent. The commercial efficiency has not yet been determined, owing to the machine having been required for service.
TESLA’S ШОВ POTENTIAL AND HXQH FREQUENCY WORE.
Fnw inventors, in this last decade of a century of invention, have made a greater impression on the popular inmgination than Nikola Tesla. Though by race a Southern Slav, he has now been settled for many years in the United States of America. From his raoe, it is to be preeomed, he inherits his soaring scientific imagination, while from bis environment he no doubt receives an extra stimulus to carry his fancies iato practical effect.
Tesla, in the early part of hia career, did some good work in connection with polyphaae currents, but some 10 years ago be turned his attention to a qqmparatively new and unexplored field, namely, the production and utilisation of alternating cariente of high frequency and high potential. Teala’s labours in Una field have up to date revealed many new and Btartling phenomena, which, tbongh they have as yet not found much practical application, may yet lead to the moat astounding social and industrial revolutions.
A letter from Tesla, giving a sketoh of his work and describing some reoent experiments, appears in the Electrical
Review (N.Y.), March 29th, 1899. From this and other sources we have derived the material for the following account of Tesla's investigations on the production of currents of extremely high potential : —
At the beginning of his work Тевіа found himself con-
fronted by three attractive linea of investigation; “there were oonneoted in series^ while the primaries of all, except
were the excessive eleotrioal pressures of millions of volts, . the first, were excite! by insulated dynamos. This,, however,
which opened np wonderful possibilities if producible, in- was found to be practically a very inconvenient arrange-
practical ways ; there were the currents of many handreds of ment. '
tboneknds of amperes which appealed to the imagination by The straight open core typs was then tried; several im-their astoniahing effects; and, most interesting and inviting proveniente in the insulation and arrangement of ooils were
of all, there were the powerful electrical vibrations with their tried, which appear to have been much the same as whàt has
mysterious actions at a distance.** tong been known to the makers of induction coils, snch as
The production of high electrical pressures was finally winding in compartments, making the insulation thicker
ohosen as, necessarily, the first step in the exploration of the where a-greater D.P. existed between adjacent parts of the
whole field. Some attention was given to Btatio electricity coil, and so on. The first real advance made by Tesla
|Fio. 2,—“Wm* Кхргвшихтй пч TrsLA'e Labobatory with ОЪвеемгs opHies POTKNTUL AND BlSH FAlQl-ЖЯСѴ.”|
Lighting & disconnected Tscnnm bnlb et 1,НЮ O.P. by high-frequencj currents' 1 photograph tshen by the light of t№ bulb itself, exposure about two seconds»
VoL 44. Ho. 1Д19, May 5.1898.]
with the experiments of Franklin as a starting point.
VariOue generators of static electricity were tried, and tome new ones, were designed.
Tesla has not as yet published any account cf these statio generato» ' which he has designed; it is to be hoped he will do so loon. The moBt valuable outcome of tbeee experiments was the discovery of a method of operating any1 kind of low tension devioes from snch high pressure sources with perfect ease and safety.
Tesla, however, soon convinced himself that his object was not te be attained by the use cf the steady pressures prod need by static machines. “It was exactly,” be says,
“ as if one attempted to drive piles into the : ground by the application of con-tinnoue pressure.
This ^wonld require outhhersome and powerful machinery, and would be very inconvenient. An inoomparebly better way of developing high pressure is by delivering violent blows as with a hammer.” Tihe kinetic energy of a hammer, when suddenly arrested, develops very high pressures, proportional to the rigidity of the body struck.
In the same way, reasoned Tesla, enormously high potentials wul be developed in the meet convenient way by the electro-magnetio energy of asnddenly arrested current. t^This turned Tesla’s attention to the on of transformers and induction coils for obtaining his high pressane. Those elnady ip existence were evidently not adequate for the end in view, so Tesla set about improving them. First he tried the dosed oore transformer. This type was soon found to have several drawbacks; the insolation could not be made very high, and a very high fnqnency was impassible. Nevertheless, an arrangement of several of these transformers in series^ was devised, by which a pressore of 200,000 volts was attained. The secondary ooils of several ring transformers appmre to be bis coil, with a unipolar; .secondary. One terminal of the secondary wire is oonneoted to the primary, the free terminal, as far distant as possible from the primary, bring nied for the discharge. A carious discovery msde by Tesla in connection with this type of coil, was that the bast nsalts were got when the secondary wire was equal to : a quarter oF the waye length, as calculated from the frequency and velocity of light. This discovery Tesla has utilised in his most reoent induction apparatus, with which he proposes to transmit electric currents through the air. It is difficult to explain this result ; it appears aa if юте- __ thing of the nature of a stationary wave cf potential, with anode at the earthed terminal, was generated in the secondary wire.
Daring these experiments Teda discovered that air played an important part in the bre&kihg down of insulation, and by the exclusion of air, and the use of insulating liquids, he was able to increase the potential to 10 times the amount, without breaking down the insnlation of the secondary. Tesla complains that the industrial world does not appear to ~ have profited by the recognition of this discovery, since no attempt has been made to utilise it in cables for high potential transmission, to prevent streamers. It is a faot that the liqaid insulation is lees in favour iupractioe than when attention «as first called to it by Teela’s experiments. It appears to have many practical inconveniences, and it is doubtful whether it is really superior to the solid insolation exoept for the high frequencies employed in the Teda apparatus. An induotlon coil with viscous insnlation was brought oat а short time ago by Rochefort and Wydts,1 and was said to be
, but it, like all the rest of such r ,rentlydropped into disuse, t of Tesla experiments with high tension tors was the coil or transformer illustrated in adjacent" In this coil the secondary coil is wound in авріШ lyh^pmoticaliy in one plane perpendicular to its axis ; its : exténfei|^erminal is earthed, and its length is made equal to gqafelfewave length. The primary consists of a few tnrae 0Г 'thick wire wound outside the secondary, lying thus adjacent (to the part of the Secondary whose potential is zero. It is with this apparatus that Tesla has made his experiments in the transmission of power through the atmosphere. The figure shows two transformers, a trans* mitter, and a; receiver. The central terminals are connected to deleted plates, », »', which require to Ьв supported at a considerable height on a kite or a balloon. Tesla thinks a
such a calamity and yet go on with hiariaxperitóMte ?.: Evidently the : Tesla transformer ІВ' wbafr Sir ЛГіНіат Crookes wants to increase our supply -afnitrates, and keep the wheat crop up to the demands of tbft world’s increaslngr population; it is to be hoped Tesla's experiments, wiffnot solve the'food problem in another: wayj hy^j»4mddg"ttie population to zero. ; j . ,
The large size illustrations we publish вЬопЬёвпкгяёшагк-; able results obtained inTeela’e laboratory by this coil. Pig. fi shows a vacuum tube giving 1,500. by
electric waves from a Tesla oscillator, photo
graph showing a part of the laboratory with a disconnected resonating coil supported on an insulating stand, and fflu-minated by the streamers produced, other coils remaining ■ unaffected. The pressure developed in the resonating coil is over half a million volts. In а віщЦаг experiment
|/■:?; Fio-.S.—“Som Expjeumnts'pf .Тіаді’в Laboіаіовѵ wit?'.OvaEmras. оѵ.Ніея Гоішіш. хкв Ніен;FasquiNov.” ■[ Phòtograpb sbowing a part of the laboratory, with a disconnected resonating ooil inpported on an insulating stand, and illuminated by the streamers produced, other coils re|
height of four miles will Ьэ sufficient. The air at such a height is supposed to break down under the enormous potentials developed, and become dissociated into a good conductor. Thu system of Tesla's has yet only appeared on paper, or, at least, no experiments on a large scale have been carried out in public. The oritioisms with which this scheme was received when announced last Kovemb^r were by no means favourable. But Tesla is a pioneer ip this field, and probably knows more about it than his critics. It is to be hoped that we shall Boon see such a practical trial of bis system as will finally determine its true value. _
Tesla bints at a fearful catastrophe which might result from the introduction of his system óf wireless transmission of power. The discharges ofhis*^pil when of an electro-ipotiye force of a few million volts, «coite powerfnl affinities in the atmospheric nitrogen, oaneing it to combine readily with the oxygen and other elements, particularly in Jthe presence of aqueous vapour. So energetio are these actions, and so strangely do auoh powerful dischargee behave, that, says Tesla, “ I have often experienced a fear that the. atmosphere might be ignited." Can Tesla seriously believe in the possibility of
Tesla grasped, without danger, ; я nodal point in a ooil developing half a million volts. Fig. i shows a receiving ooil filmmnating a vacuum tube through the human body. ;
Very few details of the construction and operation of these latest fruits of Tesla’s inventive genius have yet been published. For instance, we are left in the dark as to whether Tesla excites his high tension transformer by an alternating dynamo, or. by a oontùroons current and a contact breaker. It is evident that lately he has been giving considerable attention to the latter device, in connection with an induction coil which has been exhibited in this country, and is generally known as Tesla’s oscillator.
In 1891 Tesla patented a method of producing high frequency and high potential currents, in which' an alternating generator sends currents thrpngh'a primary, the secondary of which is in circuit with a condenser. This condenser lies also in a shunt circuit containing thè primary of a second coil and asparkgap. The discharge of the condenser across this spark' gap produces high frequency oscillations in' the shunt circuit, and. these oscillations are raised to an exceedingly high potential in a secondary coil wound round the
wattless, owing tò the. displacement of phase between the current and the electromotive' force being almost a
frcouenoy currents, which is known in this country, at least, as Tesla’s oscillator. The ,'spark gap in
eir,—Mr. Пanbury's courage In grappling' With the telephone difficulty ia ot 1 9 Government'» aoflonfn a kindred department—that which
- Ho half-and-half arrangement of Huliiddy and partial control will ba satisfactory for two reasons—it will be more expensive and. the oontrol wilt prove Dio scry
ceedingly dlffionlt to exercise sufflolwitly,close sapervision On "the man,ln possession Indeed, everything potuta to the necessity for tightening the grip ol the State in this direction, and It: la to be hoped that the Government wifi
In oertain qnartsrs that the working of the projected all-British cables Is about to be entrusted to the oampanles known as the Pender group. The supposed inertia of offlotaldenn—en idea which has been somewhat rudely dispelled by
Mr. Hanbo oourse
Ogswets with the Bouian : Government Telegraph Administration. It would seemthat the DaniihcSte®S(By ѣШйЛ-оѵеМів rlghte_in that egreemsot*»-
the empire, through whiah #11 telegraphic cómmunioatìons with our Govern-IPr ' 1 ' .....
wide (феи. it will not do for the Fends* group to plead Ignorance ot the lntf-' " ...........*■ ■ " nish oomi
But apart from oonstderatlonseil^fiblio^safety, It may^well^be^oubted The
ТІів pnlfilo have never realised what gallon opportunities a eabie'servloe pro.
___________left to the mercy of City vicissitudes
morality. There is «period In the history of many
whether any great cable service
and the sbh bud flow of City morality. Th_. _............ ,
com tante* when the Board know netting, and the Wirepullers respect nothing.
These being some of the abuses to which telegraph services are liable, it will ire weighty argument» in favour of State ownership and
Great Northern Telegraph Company,
B, Bfa Helen’s Claoe, 1,C, Aprili 18th.
second primary. It waB wìtb an arrangement snob eus this that Teela obtained the marvellouB results which be showed before the Institution of Electrical Engineers at the Boyal Inetitntion in 1892. The discharge from his apparatus appear to penetrate with ease the Ьев? iuEuIatore ; eieCtrode-leas vacuum tubes were illnminated at a distance,of several yards from the poles of his coil ; -unipolar lamps gave ont a light of dazzling whiteness, but unfortunately of very small oandle-power. It appears to be one of these unipolar lampe that is held in Tesla’s hand in fig. 2. If so, very considerable progress has been made since the Boyal Institution lecture in 1892.
It is a coil of the above type that is generally used for producing Tesla currents for electro-medical purposes. Their use for certain purposes in electro-therapeutics is said to have been highly successful. It is a curious fact that such discharges of a potential of tens of thousands of volts can be passed through the body without any injury. A satisfactory explanation of this strange phenomenon has not yet been given ; it has been suggested that it is because theee rapidly varying currents must be purely supeificiàl ; it may, perhaps, he due to the fact that such currents are almost completely
In 1898 Tesla patented an improved generator of high
hie fiist type of generator was replaced by a mechanical contact breaker* and the arrangement of the circuits was somewhat different. A condenser is connected in Bhunt in a circuit, containing a cocticnons current generator, choking coils, the primary qf the coil, and a contact breaker. When thè circuit is dosed by the contact breaker a direct current flows through the circuit.1 The circuit ів then suddenly broken, and the condenser is charged to a very high potential by the self-indnc-tton of the ohoking ooils^ , The contact breaker again closee the circuit, and the condenser'discharges through^ the primary, which, being of few turns, has a comparatively small self-indnotion. The result is, that; the frequency is considerably higher than in the ordinary induction coil wherc the ohoking coile would form part of the primary coil, Thje asdffiator hsa beeir shown mare them cube in tuie country ; it can be worked from lighting mains, and its working appears to bs highly satiefactory.
It is apparently in connection’ with this oscillator that Tesla has devoted himself to the improvement of the meobanloal «intact breaker. In his original patent, for the oscillator (No. 20,981, A.D. 1896) he describes a rotary contact breaker, which creates by its motion a current of air about the contact points, with the view apparently of removing the dissociated, air, And improving the insulation of the spark gap. It is in а тоте recent patent (No, J.2,866, A.D. 1898) on electric circnit controllers that we find embodied Tesla’s latest discoveries in this field. The contact breakers there described are mechanical, of a very elaborate construction t too elaborate, we should think, for general use with induction coile, unless their superiority to the present simpler forms is very great. Two new ideas appear to be embodied in these interrupters ; first, the break takes place in compressed air or other suitable gas, and secoid, a jet of merenry discharged against a metal plate, or another jet of mercury is u^ed to complete the oirouit. ' The metal plate is rotated by an electro-motor, and is notched bn the periphery where the jet of merenry impinges, so that contact ш broken when the jst.paBSee thKgi^pne of the notches between the teeth. Tesla has expressed a somewhat ungenerous contempt for the Wehnelt break, which has recently given such remarkable resulta in the bands of experimenters nere and abroad. Ite inferiority to Тевіа’в break appears to be known as yet'only to Tesla; in simplicity, at least, it is certainly superior.
We, however, wish Tésla success in the working ont of his grandly conceived, and if realised in practice, undoubtedly epoch-making ideas.
Thè Royal Society.—'Among the papers down for reading yesterday afternoon was опеЪу Mr. A. E, Tuttot, u The Thermal Expansion of Pure Nickel and Cobalt.”
TELEGRAPH AND TELEPHONE NOTES.
(Continued from 'page 728.)
Glasgow Telephones.—The Glasgow Chamber of Commerce last week considered the Government Telephone Bill. The chairman laid that the Bill which Mr. Banbury had introduced had dluppointed thole who deeired to iee the telephone! of the oountiy handled by a department of the Civil Service, Poet Office, or other-wlte. Tbit Bill was in some measure a retrograde step. It eeemed that the Treaeury detired not to go through with the matter at the present time, or it might he that the Bill might lead prette directly to what they desired, because the very_i)rodnotion of this measure had lowered the value if the National Telephone Company’s share# so mhch that it was a very much easier thing for the Government to buy up the Telephone Company than ft was three months ago. ’ If there had been no such thing as a National Telephone Company in existence, he quite believrdfhat the great Corporations might have gone into this business and done it very welL It was arranged to send a deputation to Mr. Hanbury On Wednesday. :
Glasgow Corporation Sub-Committee on the Opening of Streets has decided to appeal to the Bail way Соттіевіопегвagainst Sheriff Berry’s decision that the Postmaster-General fi entitled to Iky. Wires under the public streets, and that the municipality cannot attach the condition that they shall not he allotted to a licensee. The appeal will probably be heard by the Commissioners along with# sotti e what similar appeal taken by the Corp oration of Edinburgh. .
! International Complications in British Telegraph
Offices in the Far East.—The following correspondence has recently appeared in the - Timet (previous to the semi-official announoameat regarding the Pacific oable agreement):—.
hippy angary for the has to deal with the Imperial oable question. In that jfrobleffi, too, a similar solution Is obviously demanded, nainely, Stale ownership and State exploitation.
and. inefficient Owing to the conditions, surrounding cable work It is exnot веек to make a devointfon.of its Imperial responsibilities upon.any company or corporation whatsoever. 1
Humour bat been busy with tbi* subject lately, and It Is confidently affirmed
mbury—gave an air of probability to tbe rnmoor. It Is true tbit, the Bourse foreshadowed would sere the Government a world of trouble, but there ale consideration# which do most effectually put that' group out of court. This Is not the place to enter on a review of their treatment of the public And the Press—that Is another story i I nler to a matter of more Importance than either, *-■' . .
боте vests ago the Pendei gtonp effected an amalgamation of office, fioHong long with the Great Nbrhern Telegraph Company ol Copenhagen, whose cable
Hassle, inasmuch as the company's representative In Londòn deelaredlnan interview some months age that the oable worked from thè joint office and oed as a Danish cable Is now Russian property. Consequently the
_______group are responsible for the existence of this dangerous anomaly—that
Russian officiala are admitted to an Important telegraph office in an outpost of meut, public, and Press must necessarily pats! ; Them, at any rate, the door is mate relations existing between the Danish company and the Russian Government s that was a matter ol common knowledge in China long before the amalgamation, sent# to tbe latter; they can favour certain Olfehts at the expense of others! they .ran ran rivalry with clients in their legitimate business, and they oan appropriate the clients' property, ‘We do -net suppose that cable oompShiea diner greatly lrom others as regards their management, but Ihis we do know, that no other condition» oliar each temptations, nor render detection so difficult.
be seen that there are State exploitation.
The colonies, I understand, are ready to provide five-ninths of the subsidy for the projected cable*. To the Government I say, with all re spool, “Do not pnt ohr money on the wrong borse.1’ ...
Tent obedient servant,
вігс-тТЬв letter In your issue ot Saturday, April l»l( andar the above heading, signed "Colonial," states that the Great Northern Telegraph Company's ‘iiepresantatdve In London " declared in an Interview some months ago that the oable Worked from the joint office (In Hong Kong), and Introduced as a Danish cable, la now Ressi an property..
- Permit me to point out—first, that I am not awars of having had any Interview " with anybody on the subject referred to for a Whole year, or not since April, 1888 ana the gist of my observations on that occasion to a representative of the Wertmintier emette, as quoted in that paper ot April STth, 1898, was quite the reverse of the statement attributed to me by " Colonial;" seoondly, that I never made, nor oould have made, any such staftment-—(I; because, ae pointed outat the sud interview, one of the very objeotsol the joint working arrangement ol the two companies in the Tar Bast was to leave the leadership and control of tbe Hong Kong station to the Britleh oompany (the Bantam Extension Telegraph Company) ; (U) because' the oable from Hong Kong to Amoy and further to Shanghai, Japan, and Siberia ii.and always has been, the property of the Danish company, the Great Northern Telegraph Company, in whose service there Is not a single Russian, tput a number or Englishmen, and whose shares are more largely held in this than in any other oountry, while not a single Share Is held In Husstn.
As to the relatione of the oomnany with foreign Governments, they are, happily, as intimate with the British as with the Bussian and other Governments on .whose territories our oables are landed.-The other invidious insinuations of "Colonial" I may safely leave unanswered ;. they are beneath notice. .
I am, Sir, your obedient servant,
- F. О, C. NixnssH, the company’s representative in England,
Klnotbjcal Rbvibw, 43, у.105.