Nikola Tesla and the induction motor

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Nikola Tesla and the induction motor

C Mackechnie Jarvis C Mackechnie Jarvis and Partners London

Seventy seven years have elapsed since Nikola Tesla visited London for the purpose of lecturing before the IEE on the subject of ‘Experiments with alternate currents of high potential and frequency’. In those days, normal meetings were held in the former build- ing of the Institution of Civil Engineers but, as a large attendance was expected and the facilities needed for demonstration were considerable, the meeting on the 3 February 1892 was held at the Royal Institution.

Tesla was in his 36th year and had achieved a splendid reputation in the USA. In England he was little known and for some reason, the technical Press, if not antagonistic, was grudging in its recognition of his originality and genius.

Early years Nikola Tesla was born on the 10 July 1856 in Smiljan, a village in the border province of Lika, now in Yugo- slavia, but then forming part of the Austro-Hungarian empire. He was the son of a clergyman of the Serbian Orthodox Church and the grandson of another. Understandably, his father hoped that Nikola would follow his example and enter the Church, but in this he was later to be disappointed. Tesla’s mother, although the daughter of a clergyman, is understood to have been illiterate, but is reputed to have possessed the phenomenal memory so often associated with people of more isolated communities. Although unable to read, she could, it is said, recite long passages from the Bible and other books learned by heart, and she practised, with Nikola, a process of thought trans-

This article is based on a lecture given by the author before the History of Technology Group of the Institution of Electrical Engineers on the 14 March 1969 and reproduced here by kind permission of the IEE and the author. 280

ference of which remarkable examples are on record. Tesla’s father possessed a large library and was widely read. In addition to his native Serbo-Croat, he could read and converse in the official language of the province (German) and in French and Italian.

Against this background, in many respects a parallel to numerous instances which occur in Scottish history, emerged a typical child of the manse, avid for knowledge, receptive to a high degree, and remarkable for his mental ability to absorb and retain much of what he had read, which it is said he could quote verbatim years later. Like his father, he became fluent in German, French and Italian, and at somesubsequent period, while still at college, acquired a knowledge of English which was to stand him in good stead within a very few years.

His amazing mental powers were evident at an early age when it was found that, to the early suspicion of his masters and to their subsequent admiration, he

Fi<yure 1 Nikolu Tesln ( 1856- 1943).

could write down the answers to quite complicated mathematical problems.

During his lifetime Tesla was induced to write accounts of his early years and, although these are sketchy, he describes his determination to exclude from his life all normal human emotions as far as he could, and so become a ‘superman’. He did not allow close friendships to develop for the reason that they tended to waste time which he could ill afford to spare from his studies and experiments, and needless to say he did not marry.

He tells us that his interest in the possibility of designing a motor which could run on alternating current arose directly from his observation of the performance of a laminated permanent magnet dc machine with a Gramme-ring armature acquired by the Joanneum at Graz, where he was a student during the winter term of 1878. This small demonstration machine, first marketed for laboratory use by M Breuget of the Gramme CO, was used for a variety of experiments, both as a dynamo and a motor, and performed with what Tesla has described as ‘lively sparking’ at the commutator. Tesla says that it occurred to him then that if the commutator could be eliminated a much more satisfactory machine would result.

Electrical machines At this point it is convenient to examine the state of the electrical art in Europe at this time. It will be recalled that quite large permanent magnet dynamos with low outputs (less than 2 kW) had been construc-

ted for supplying arc lights for lighthouse service by Holmes (Dungeness in 1862 and Souter Point in 1867) and a permanent magnet alternator for Souter Point in 1870. In 1870-71, the early Gramme dynamos of commercial size appeared and within two years the Siemens concern in Berlin had marketed a range of dynamo-electric machines for dc working, one of which was exhibited at the Vienna International Exhibition of 1873.

H Wilde (1833-1919) in England had patented and manufactured several types of alternator since 1867, and a much improved alternator by Gramme was marketed in 1878, initially for supplying Jablochkoff candles (a form of arc light of low current consump- tion), first used in Paris in 1876 and in London in the following year. Siemens alternators were available in 1878, and the Ferranti alternator with the zigzag winding was available in 1881. All these were, of course, single phase machines. Thereafter progress was rapid, both in terms of the number of different manufacturers entering the field, and the sizes of the machines produced.

We must now revert to the year 1824, when F J D Arago (1786-1853) noted the damping effect on a magnetic needle when suspended in proximity to a sheet of copper. Having reasoned that if a stationary mass of copper could bring a moving magnetic needle to rest, a moving mass of copper ought to set a station- ary needle in motion, he tried this experiment in 1825, and found that a rotating copper disc would cause a magnetic needle mounted above it to follow the disc. Very shortly afterwards, (Sir) John F W Herschel

Figure 2 Threephase induction motor from thrjrst US acpatent, 1 May 1888.

28 1

(1792-1871) varied the experiment by substituting a horseshoe magnet for the magnetic needle and demonstrated a similar result. The experiments took their place in therepertoireof‘physics’demonstrations, and became known familiarly as Arago’s ‘rotations’.

The work of Faraday in this field is well known, and the principle of electromagnetic induction was enunicated in 183 I , giving rise to the invention of the practical dynamo and from it the dc motor.

In 1879, Professor Walter Baily propounded a variation of the Arago experiment in which the rotating permanent magnet was replaced by four electromagnets arranged at 90” intervals below a disc which was free to rotate. The exciting coils were fed from a battery via a hand operated rotary-pattern switch, the connections being so arranged that when the switch handle was turned a rotating field was produced, and this induc5.l motion in the disc.

The device was first demonstrated a: a meeting of the Physical Society in London on the 28 June 1879; whe:? questioned by one of those present ;S to its utility, Baily replied that he rc- garded it only as a scientific toy.

The young engineer In 1880 Tesla entered Prague University where he appears to have spent only on: year. In 1881 he was working with th: Department of Posts and Telegraphs in Budapest, and by 1882 he had found his way to Paris. He obtained an introduc- tion to the Continental Edison CO, an5 on their behalf travelled to Strasbourc where a small generating station and street lighting network had been estab- lished and were giving trouble. Tesl:l says that the idea of the induction motor occurred to him in Budapest and that he made and demonstrated his first work- ing models while in Strasbourg. There is slight dificulty in accepting this stat+ ment because the Edison installation; were exclusively for dc working and Tesla would have needed access to an ac supply to demonstrate his model induc- tion motor as he says he did. I t is possibl: that he made a two phase alternator as well, and ran this to feed the motor.

Figure 3 Two phase synchronous mofor from rhesecond USacpafent, I May 1885. 282

At this period, the chief executive of the Paris company was Charles Batchelor, an Englishman by birth who had emigrated to the United States in the early 1870s and had later joined Edison. Batchelor had been sent to Paris to take charge of the Edison exhibit at the great electrical exhibition in 1882, and had remained to establish a lamp factory and machine works near Paris, which became operative in August 1882.

There is an account of Tesla’s arrival in Paris in ‘Menlo Park reminiscences’ by Francis Jehl, one of Edison’s engineers:

‘One day a tall, lanky young man came out to the factory and handed in a letter from Karl Puskas of Budapest. He used to tell us what a grand thing it would be if one could use ac and have motors without

commutators. We told him that we thought so also, but that he should use his brains now in getting all the information possible about the Edison system and then get to work.

‘He had an aversion to running wires or making installations and it did not suit him when he was sent to Strasbourg to assist in the work there. Up to that time Tesla was used to those congenial conditions then in vogue in Austro-Hungary, the motto being “If I don’t come today, I’ll come tomorrow”. Tesla did not like the American activity that Batchelor had brought into the French Edison works there, and when he (that is Tesla) came there, the place had not the lure for him that he thought an Edison place would have . . . It turned out that the German officials (in Stras-

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No. 390,721. Patented O o t . 9, 1888. D Y N A M O E L E C T R I C M A C H I N E .

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bourg), who were used to discipline, complained to the Paris office that Tesla passed the golden morning time when he ought to have watched the work in the arms of Morpheus!’.

It is fair to state that this comment on Tesla’s nature is not borne out by any other account of him; in fact, the converse is the case.

Tesla and Edison In 1884 Tesla decided that if he could reach the USA he would probably be able to develop his ideas more successfully, and with money sufficient only for his passage he sailed in the summer of 1884. Upon arrival, in a penniless state, he worked in the Edison factory for a time, but soon discovered that to his principal the very mention of alternating current was anathema. It has been stated that Edison thought of ac as some- thing so abnormal as to be impossible of practical use and he is supposed to have said ‘how can they reverse the direction of the current ?’.

Edison’s position vis-&vis alternating current was also made clear in an article published in an American periodical, in which he is quoted as saying:

‘The Electric Lighting Company with which I am connected purchased some time ago the patents for a complete ac system and my protest against this action can be found upon its minute book. Up to the present time I have succeeded in inducing them not to offer this system to the public, nor will they do so with my consent’.

There was clearly no hope for Tesla within the Edison organization and soon after he was able to

F , ”. ;l secure some financial backing, allowing him to leave

Edison and to establish his first independent concern under the style of ‘The Tesla Electric Light and Manufacturing Company of Rahway, New Jersey’ in 1885.

During the short life of this company, Tesla was granted five US patents for improvements to dc machines and two for arc lamps. Tesla was induced to assign his patents to the company in return for share certificates, which he later found to be worthless. The concern failed early in 1886 and for a time Tesla suffered considerable privation, finding it necessary to work for a period as a labourer on road construction.

A more reliable financial connection was established in 1887 and on the 12 October of that year the inventor WITNESSES:

q+?admr lNVENTOR filed the first of a series of 38 US patents which form RW.5 G”L the subject matter of this article. -. The initial US patent for ac machines (381968) was

6 ATTORNEY&! granted on the 1 May 1888 and was recognized as Figure 4 Two phase, four wire distributionfrom containing material of a novel kind relating not only sixth USacpatent, 9 October 1888. to a new source of notive power but also to a new

283

concept in power generation and transmission. The US Patent Office required this, and at least two of Tesla’s later applications, to be divided to separate the concepts of electrical generation and transmission from that of utilization of power in a motor, and patent 381968 should therefore be read with patent 382280 of the same date.

The importance of Tesla’s first patent cannot be overemphasized, as it virtually covers a complete polyphase system comprising an alternator and an induction motor with alternatives of a solid and a wound rotor. Tesla’s invention of the synchronous motor is the subject of a further patent (381969), also granted on the 1 May 1888. In the other patents belonging to this period are to be found the polyphase power transformer, the polyphase induction regulator, the use of slip rings and tappings on a dc armature to provide a two phase or three phase ac supply, the use of a com- mon return for a two phase/three wire system, and the star connection of three phase machines.

In 1889, there were several patents for single phase induction motors for split phase starting and for a rotor with a slotted periphery. In 1891 the use of a capacitor for power factor correction was patented in both stator and rotor combinations. By what appears to be a US Patent Office oversight, a claim in 1887 for a single phase motor with a highly inductive starting winding was not recognized until the grant of a patent in 1894.

Almost immediately following the publication in the USA of Tesla’s first patents in 1888 and reports of his paper before the American Institute of Elec- trical Engineers read on the 16 May 1888, rival investigators and manufac- turers entered the field in the USA and in Europe.

Tesla and Westinghouse George Westinghouse ( I 846-1914) had become interested in the possibility of ac distribution, probably as a result of publicityarisingoutoftheLondonInven-

Figure 5 Split phase starting o f a single phase motor (also a two phase, three wire system with Earth return) from the tenth US ac patent, 16 April 1889.

284

tions Exhibitions of 1885, at which high voltage trans- mission was demonstrated by Gaulard and Gibbs with primitive movable core, single phase, series connected transformers. This apparatus was currently being used in London as part of a single phase system supplying arc lighting in the stations of the Metropolitan Rail- way.

In Europe, Dr Werner Siemens was strongly oppo- sed to the use of alternating currents which he regarded as ‘pure humbug’; but, on the other hand, the Buda- pest firm of Ganz, run by the famous engineers 0 T Blathy (1860-1939), M Deri (1854-1938) and K Zipernowski (1853-1942), was strongly in favour of ac, and was manufacturing single phase alternators and transformers.

As soon as he heard of the activities of Nikola Tesla,

Westinghouse sent a representative to view his ac motor and to report on its commercial feasibility, the outcome of which was the outright purchase of the Tesla patents on terms advantageous to the inventor, who spent a year at the Pittsburgh factory with the object of producing a range of commercial motors. In this aspect of the development Tesla was unsuccessful; it is probably that, by nature, he was quite unable to work as a member of a team, and lacked experience in the practical design of rotating machinery on a commercial scale, which his colleagues, as a result of their experience of dc machinery, possessed. It was also found that the induction motor was quite unsuitable

Figure 6 A Tesla motor with distributed stator winding and wound rotor developing approxintately 0.25 hp at 1800 rev min-l, circa 1889. (Photo: Science Museum).

Figure 7 A rotor of the Tesla motor shown in figure 6 (Photo: Science Museum).

for traction purposes in which there was, at this time, a ready market, and this was an unexpected blow to Westinghouse. Furthermore, the motors did not perform well on the 100 Hz system Westinghouse and others had adopted for single phase lighting.

Tesla favoured the two phase motor as distinct from the three phase type, but with either system there was, at first sight, what appeared to be an insuperable difficulty, as an additional main was necessary com- pared with a dc system. Ultimately the advantages offered by ac in respect of hv transmission and distri- bution outweighed such early considerations.

Having secured the patent rights, Westinghouse

Fikrrrre 8 Westingl~orrsc indrrc/ion motor built to Tesla patents, 1892.

285

found himself in financial difficulty owing to other investments in the industry and several years elapsed before the Tesla motors were adequately marketed in the USA in 1892. An earlier Westinghouse single phase installation at Telluride Colorado, completed in 1891, is, however, notable in that it comprised a water turbine driven alternator and 3000V transmission over 4 miles to a mine to feed a 100 bhp synchronous motor started by a split phase pony motor. Typical of the rate of progress in the USA is the 10 kV trans- mission line of 1893 and the gigantic Niagara Falls project, for which contracts with Westinghouse for 2200 V two phase alternators driven by 5000 hp water turbines were placed in the same year.

Meanwhile, in Europe, Ganz of Budapest, AEG of Berlin and, in Sweden, the Wenstroem CO (later the ASEA) became extremely active in the ac motor field.

One cannot escape the fact that the enormous achievement of Tesla on so broad a front aroused very considerable animosity, particularly in Germany, and this had nothing whatever to do with the enforcement of the Tesla European patents by his licensees, which gave rise to irritation subsequently.

The German engineers, particularly Michael Dolivo von Dobrowolsky (1860-1919), chief engineer of Emil Rathenau's organization (AEG) and his friends, were particularly antagonistic and repeatedly claimed credit for the success of the induction motor and for the invention of the three phase connection (Drehstrom), but clearly they were anticipated by Tesla.

The principal improvements made by the European inventors reflected by British patents are as follows,

1889: patent 10933 ; M D von Dobrowolsky: single and treble conductor squirrel-cage rotors

1890: patent 5423 ; Jonas Wenstroem : three phase distributed stator winding; delta connection as alter- native to star; rotary convertor described as such

1890: patent 20425; M D von Dobrowolsky: liquid resistances for slip ring motors for speed control.

Unquestionably, European firms led the world for a time, and from the constructional aspect alone, German and Swedish motors enjoyed a high reputa- tion.

Controversy Much of the fame due to Tesla was marred by claims for priority of invention of the induction motor advanced by protagonists of the Italian Galileo Ferraris (1 847-97), a professor of electrical technology at the Industrial Museum, Turin. It appears to be 286

generally agreed that Ferraris had been seeking a means for demonstrating, in model form, the nature of polarized light, and it occurred to him that a 90" dis- placement in an electrical circuit could readily be made to create an analogy with the phase displacement occurring when light is polarized. There is dispute as to when Ferraris first made and demonstrated his model, in which a copper cylinder suspended on a thread was acted on by two electromagnets placed 90" apart, parallel with the axis of the cylinder.

It is known that Ferraris later mounted the copper cylinder on a shaft placed within a rectangular frame carrying four coils displaced at 90" with respect to each other. Opposite coils were connected in series to form two pairs, which in turn were fed from a single phase source. Phase displacement in one pair of coils was obtained by the interposition of an inductance coil. Ferraris and his friends claimed that the models were demonstrated in Turin in the late summer of 1885.

According to J J O'Neill, Ferraris predicted no future for the device as a power source, but thought it might find application as the operating principle for an electricity meter. To the historian, however, the fact remains that Ferraris did not publish his discovery until 1888 when, on the 18 March, he lectured before the Royal Academy of Science in Turin. In his paper, he clearly established his discovery of the rotating magnetic field produced by alternating currents independently of Tesla, but it appears that he did no more than demonstrate that motion could be produced therefrom, and left it at that.

Tesla, for his part, set out to produce a practical motor without a commutator, and succeeded. The opportunity which Ferraris neglected to exploit has understandably remained as a source of disappoint- ment to our Italian confreres.

Tesla, by his own nature, failed to reap more than a meagre return for his work. After the induction motor period, he became far more interested in scientific achievement than in commercial success, and in later life he appears to have made no attempt to collect royalties from those using his numerous inventions, although he was frequently badly in need of money and heavily pressed by his creditors.

Recognition It is well known that Tesla's patents were infringed on a wide scale, and although in Germany the courts decided against Tesla, in the USA the Westinghouse CO brought a series of successful actions. B A Behrend, formerly chief engineer of the General Electric CO of America, published in his book The induction motor

(1921) the following apologia : ‘It became incumbent upon the writer, more than 20

years ago, to appear as though he gave countenance to the infringement of the fundamental Tesla patents. A large number of induction motors designed by him during the life of these patents, which constituted a plain infringement of Tesla’s inventions, have no doubt been pointed to as an indication that he either did not believe in the validity of these patents or that he deliberately became a party to their infringement.

‘The company of which, at the period referred to, he was chief engineer owed its growth and develop- ment largely to his personal efforts in the design and development of electrical machinery and to his success in organizing an effective engineering staff. . . In due course, the owners of the Tesla patents proceeded against our company, and in the long litigation which followed the writer’s position was at times embarrass- ing and disagreeable.

‘By way of epilogue, he begs leave to publish now, with bitterness of the controversy abated, a letter addressed to the patent counsel of his company:

Cincinnati, Ohio, 23rd May 1901 Mr Arthur Stem Patent Attorney City My Dear Sir,

Enclosed please find my notes on the Record of Final Hearing in the suit of Westinghouse Electric & Mfg CO versus the New England Granite Co.

You will see that I am now, even more than I have been before, of the opinion that it is not possible for us to bring forth arguments that couldgo to show the invalidity of the Tesla patents in suit. While I am, as engineer in charge, perfectly willing to give you all the technical assistance in my power that you might need or ask for, I cannot undertake to give expert evidence in this case in favour of my concern, as such evidence would be against my better conviction in this case. As, during my last call at your ofice, you intimated my being one of the experts, I think it best to let you know as early as possible that I cannot undertake this duty.

I remain, yours very truly, B A Behrend Chief Engineer etc. G E Co.’

Tesla’s scientific achievements received recognition in many ways. He received doctorates from 14 universities and was awarded the Edison Medal of the American Institute of Electrical Engineers. He died in New York on the 7 January 1943 in his 87th year.

In the land of his birth, a museum has been estab- lished in Belgrade, and here are preserved most of his surviving notebooks and papers. The Science Museum in London possesses a small single phase motor with wound rotor, made by Tesla and presented by him to Professor Ayrton, who was in the chair at the London meeting in 1892. Other early machines and papers were destroyed in the lire at Tesla’s laboratory in 1895, but a few motors have survived at Pittsburgh.

Nuffield advanced physics project

There is a need to arrange that some schools can start the A level physics course in September 1971, prior to publication in early 1972. These schools are those presenting candidates for the Nuffield 0 level examin- ation in Summer 1971 and wishing to start the A level course in September 1971. In these cases it may be possible for copies of the trials materials to be supplied at cost. There are, however, severe limitations on the number of schools we can supply in this manner. For LEA maintained schools the support of their LEA for this early start is essential. In addition it would be possible for a small number of Colleges of Further Education to start the Nuffield A level course in September 1971.

Further information can be obtained from W Bolton, Nuffield Foundation Advanced Physics Project, 90 Lillie Road, London SW6.

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