DOCSLIB.ORG

Titre De L'article

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Titre De L'article The invention of the synchronous motor by Nikola Tesla by Ilarion Pavel Chief Engineer, Corps des Mines Research Fellow at the Laboratory of Theoretical Physics École Normale Supérieure Figure 1: The front cover of a special issue of Time Magazine published on 20 July 1931, marking Tesla’s 75th birthday (© Time Magazine, New York). Nikola Tesla (1856–1943), born in the Croatian town of Smilijan, then part of the Austrian Empire, was the fourth of five children of a Serbian Orthodox priest. After studying at the Graz University of Technology and the University of Prague, he worked as an engineer in Budapest and Paris, where he tried, unsuccessfully, to develop his ideas on alternating current (AC) and the rotating- field electromagnetic motor. In 1884 he emigrated to the United States, where he would stay the rest of his life. He joined Thomas Edison’s (1847–1931) electric company, but Edison, who had devoted his business affairs to direct current (DC), did not look favourably on the young Serbian’s ideas. Disappointed, Tesla left Edison for George Westinghouse’s (1846–1914) firm. At this time Edison and Westinghouse were engaged in a fierce battle to develop an electricity 1 distribution system, a battle Westinghouse would win. The creative Tesla authored and contributed to many inventions: the induction motor, the AC distribution network, radio, wireless communications, and remote-controlled robots. A BRIEF HISTORY OF ELECTRICITY AND MAGNETISM One day in April 1820, in Copenhagen, the Danish physicist Hans Christian Œrsted (1777–1851), during a lecture to his students, connected a galvanic battery to a platinum wire placed just above a compass. In disbelief, the students saw that the electric current passing through the wire deflected the compass needle in a manner analogous to the Earth’s magnetic field. A potential link 1 between electrical and magnetic phenomena had been discovered. Figure 2: Œrsted’s experiment. When the circuit is closed (right-hand image), the electrical current passing through the conductor produces a magnetic field, which interacts with and deflects the compass needle. The needle aligns perpendicularly to the conductor (© Ilarion Pavel). This discovery was not a matter of luck, but the fruit of many years’ research. A follower of Naturphilosophie, Œrsted was convinced that various observed mechanical, electrical, magnetic and chemical phenomena were simply different manifestations of a single, fundamental unitary force. Œrsted had the 2 insight to use galvanic cells in his experiments rather than the electrostatic machines or Leyden jars used by other physicists, which produce currents too weak to demonstrate magnetic phenomena. Electrostatic machines generate high-tension but weak and temporary currents. Since magnetic effects are 1. For an analysis of Œrsted’s text (1820), see J.-J. Samueli and A. Moatti, “L’acte de naissance de l’électromagnétisme”, BibNum, January 2010. 2. This article uses the terms galvanic cell and galvanic battery interchangeably. 2 proportional to the intensity of the current, it is practically impossible to demonstrate such effects using this type of equipment. Œrsted’s results received a muted reaction when Francois Arago presented them at a meeting of the Academy of Sciences of Paris in 1830. Most of the Academy’s members, influenced by the work of Charles de Coulomb, believed that there was no link between electrical and magnetic phenomena. André-Marie Ampère did not share this scepticism and embarked on a tireless round of experimental and theoretical inquiries. After a few weeks, he was able to understand and quantitatively express the links between electric currents and 3 magnetic fields, leading to his invention of electromagnetic equipment such as 4 5 the galvanometer and the solenoid . On the other side of the Channel, William Sturgeon (1783–1850) discovered that placing an iron bar inside a solenoid spectacularly increases its magnetic field, thereby inventing the electromagnet. As its name indicates, the electromagnet, which is powered by a galvanic cell, produces a magnetic field, one strong enough to lift iron pieces, for example. The electromagnet can thus perform a mechanical action using electric energy. It would play a crucial role in the development of the electric motor. Figure 3: Sturgeon’s electromagnet, made out copper turns wound around an iron horseshoe-shaped core, could lift 4-kg weights. The electromagnet uses mercury cup connectors annotated Z and C (the third cup, on the left, which is connected to the magnet by rod d, acts as a switch. The copper wire is non-insulated and the iron is lacquered to prevent a short circuit between the turns (WikiCommons Illustration). 3. See the Technical Annex at the end of the article. 4. The galvanometer is made from a compass needle placed inside the coil. When an electric current passes through the coil, this creates a magnetic field which deflects the needle. The intensity of the current is calculated by measuring this deflection. 5 The solenoid is made out of a conductor wire wound helically around a long cylinder. When powered by a galvanic cell, it produces a stronger and more homogenous magnetic field than a simple loop of conductor wire. 3 Across the Atlantic, Joseph Henry (1797–1878) was building ever more powerful electromagnets, reducing their size and increasing the magnetic force. Prefiguring the use of insulated electric cables, Henry wound compact and multiple layers of silk-insulated copper wire around a coil. This significantly increased the strength of the magnetic field even though the energy source was still the same modest galvanic cell. In no time at all the characteristics of Henry’s electromagnet exceeded those of permanent magnets. They were principally used in research laboratories or in public demonstrations: one spectacular demonstration consisted in suspending an iron bar, weighing some several hundred kilograms, using electromagnetic attraction. When the power supply was removed, the bar crashed to the ground. In addition, some electromagnets were commercialised: one of Henry’s was used by Penfield and Taft Ironworks (Crown Point, New York State) to magnetise steel cylinders used in the extraction of iron from its ore. THE INVENTION OF THE ELECTRIC MOTOR 6 A rotating mechanical system was first developed by Michael Faraday (1791–1867) in 1821, in his attempts to demonstrate that electric current passing through a wire generates a circular magnetic field. Faraday fixed a magnet bar upright in a cup filled with mercury and freely suspended a rod conductor above, so it was just touching the surface of the liquid. When he connected the rod to a galvanic cell, Faraday noticed that it revolved in circles around the magnet. This motion is due to the interaction between the current flowing through the rod and the bar’s magnetic field. This was the first example of a device that converted electrical energy into continuous mechanical motion. However, no practical applications were developed and the apparatus remained confined to the laboratory. 6. See Technical Annex, Figure A1. 4 Figure 4: Faraday’s electric motor. The current provided by the battery flows through the suspended conductor rod and interacts with the magnetic field produced by a magnet immersed in the mercury filled cup. As a result, the rod rotates on its vertical axis. The electric contacts are provided by the frame and the rod gently touching the mercury surface (© Ilarion Pavel). 7 In 1831, Henry invented the first electric motor. The mobile part of the electromagnet oscillates on its horizontal axis. The magnet’s polarity automatically inverses as it moves due to the action of two pairs of conductor wires that are connected alternately to two galvanic cells. Two permanent vertical magnets with their poles oriented in the same direction alternately attract and repel the ends of the electromagnet, making it oscillate from side to side. Figure 5: Henry’s oscillating motor. Two permanent magnets (C and D) are fixed in place with their north pole pointing upwards. When the electromagnet is supplied by the battery on the right, its north pole B is pushed upwards by the D magnet, and its south pole A is attracted downwards towards the C magnet. This makes the electromagnet swing: the circuit is broken at the right battery and re-established in the left battery, and the batteries are connected in such a way that the electromagnet’s north and south poles are reversed. The north pole A is thus repelled by the C magnet and the south pole B is attracted to the D magnet. The electromagnet swings the other away, cutting off the electricity supply from the left battery and re-establishing it in the right battery, and the process starts again. The electric contacts are provided by the metal rods q, r, o and p, joined to the oscillating electromagnet (© American Journal of Science). 7. J. Henry, American Journal of Science and Arts, 20, 340 (1831). 5 THE ELECTRIC GENERATOR ARRIVES ON THE SCENE Œrsted demonstrated that as long as an electric current flows through a conductor, it generates a magnetic field. In the true spirit of the unity of forces, adepts of Naturphilosophie immediately wondered if the opposite were true: can a magnet’s magnetic field generate an electric current in a nearby inductor coil? The results of the first experiments were negative for they involved little more than placing a coil around a magnet, and the galvanometer registered no current. 8 It was only after several failures that Faraday announced his success, in 1831. His method consisted in winding two separate coils around a common metal core. One of the coils was connected to a galvanometer, the other to a battery. When he connected or disconnected the battery, the galvanometer’s needle would deflect momentarily and then returns to zero.
Load more

Recommended publications
  • Sparks, Shocks and Voltage Traces As Windows Into Experience: the Spiraled Conductor and Star Wheel Interrupter of Charles Grafton Page
    | Sparks, Shocks and Voltage Traces as Windows into Experience | 123 | Sparks, Shocks and Voltage Traces as Windows into Experience: The Spiraled Conductor and Star Wheel Interrupter of Charles Grafton Page Elizabeth CAVICCHI a T Abstract When battery current flowing in his homemade spiraled conductor switched off, nineteenth century experimenter Charles Grafton Page saw sparks and felt shocks, even in parts of the spiral where no current passed. Reproducing his experiment today is improvisational: an oscilloscope replaces Page’s body; a copper star spinning through galinstan substitutes for Barlow’s wheel interrupter. Green and purple flashes accompanied my spinning wheel. Unlike what Page’s shocks showed, induced voltages probed across my spiral’s wider spans were variable, precipitating extensive explorations of its resonant fre - quencies. Redoing historical experiments extends our experience, fostering new observations about natural phenomena and experimental development. Keywords: electromagnetic induction, historical replication, Charles Grafton Page, exploratory learning, spiral, Barlow wheel, galinstan, autotransformer T Introduction real? Facing wires and wiggling magnetic needles firsthand, while trying to make sense of it, deepens Historical experiments come to us in fragments: our perspective; we become confused and curious handwritten data, published reports, and often non - (Cavicchi 2003). Redoing an experiment is not just a functioning apparatus. A further carry-over may per - check on facts, dates, whether Oersted’s needle went sist in ideas, procedures, materials and inventions east or west. It gives us access to experience congru - bearing imprints of the prior work. All these are clues ous with the past: “’to know an experimenter, you to something both more transitory and more coher - should replicate her study’” (Kurz 2001, p.
    [Show full text]
  • The Art of Books Bindings.Lib.Ua.Edu
    Publishers’ Bindings Online, 1815­1930: The Art of Books bindings.lib.ua.edu Sample Lesson Plan: Industrial Revolution Grades K­12 * Teachers of elementary students may modify the wording to a level better understood by younger children and omit the discussion questions. * Students in grades 6­12 should be given up to a week to complete their activity; reporting on their activity will take a second class period. Objectives: • Students will learn about the changes that took place during the Industrial Revolution. • Students will learn how book bindings reflect society. Materials: 1) A computer with an Internet connection and a large screen or other capability to display the teacher’s actions to the entire class. 2) For 6­12 only: Chalk board or dry­erase board and appropriate writing implement. 3) For K­5 only: Enough blank paper for each student. 4) For K­5 only: Crayons, markers, or colored pencils (either for each student or to share). 5) For K­5 only: Corkboard and tacks or other capability to display student artwork (such as spreading it out on a large table or taping it to the wall). Lesson Introduction Media often reflect the society in which they are created, and books are no different. Book bindings produced during the American industrial revolution symbolize and reflect the incredible changes that took place during this era. Historians note that the period from the Civil War’s end until roughly 1920 was marked by a movement toward production of goods by machine rather than by hand, usually in large, intricately­organized factories.
    [Show full text]
  • Joseph Henry
    MEMOIR JOSEPH HENRY. SIMON NEWCOMB. BEAD BEFORE THE NATIONAL ACADEMY OP SCIENCES, APRIL 21, 1880. (1) BIOGRAPHICAL MEMOIR OF JOSEPH HENRY. In presenting to the Academy the following notice of its late lamented President the writer feels that an apology is due for the imperfect manner in which he has been obliged to perform the duty assigned him. The very richness of the material has been a source of embarrassment. Few have any conception of the breadth of the field occupied by Professor Henry's researches, or of the number of scientific enterprises of which he was either the originator or the effective supporter. What, under the cir- cumstances, could be said within a brief space to show what the world owes to him has already been so well said by others that it would be impracticable to make a really new presentation without writing a volume. The Philosophical Society of this city has issued two notices which together cover almost the whole ground that the writer feels competent to occupy. The one is a personal biography—the affectionate and eloquent tribute of an old and attached friend; the other an exhaustive analysis of his scientific labors by an honored member of the society well known for his philosophic acumen.* The Regents of the Smithsonian Institution made known their indebtedness to his administration in the memorial services held in his honor in the Halls of Congress. Under these circumstances the onl}*- practicable course has seemed to be to give a condensed resume of Professor Henry's life and works, by which any small occasional gaps in previous notices might be filled.
    [Show full text]
  • (12) Patent Application Publication (10) Pub. No.: US 2003/0143413 A1 Storbeck Et Al
    US 2003.0143413A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2003/0143413 A1 Storbeck et al. (43) Pub. Date: Jul. 31, 2003 (54) PRODUCING PRESSURE-SENSITIVELY (30) Foreign Application Priority Data ADHESIVE PUNCHED PRODUCTS Nov. 22, 2001 (DE)..................................... 101 57 1534 (75) Inventors: Reinhard Storbeck, Hamburg (DE); Marc Husemann, Hamburg (DE); Publication Classification Matthias Koch, Hamburg (DE); Maren Klose, Seevetal (DE) (51) Int. Cl." ........................... B32B 27/00; B32B 27/30 (52) U.S. Cl. ............................................ 428/500; 428/522 Correspondence Address: KURT BRISCOE NORRIS, MCLAUGHLIN & MARCUS, PA. (57) ABSTRACT 220NEW EAST YORK, 42ND NY STREET, 10017 (US) 30TH FLOOR A process for producing preSSure-Sensitively adhesive punched products from backing material coated with pres (73) Assignee: tesa Aktiengesellschaft Sure Sensitive adhesive, wherein Said pressure Sensitive adhesive is oriented Such that it (21) Appl. No.: 10/219,523 possesses a preferential direction and, (22) Filed: Aug. 15, 2002 the punching process is carried out continuously. Patent Application Publication Jul. 31, 2003 Sheet 1 of 5 US 2003/0143413 A1 var- - - - - - - - - - mm Et= SOC kW Siga A - 726.6nm WD = 5 m Signal B = Fig. 1 Patent Application Publication Jul. 31, 2003. Sheet 2 of 5 US 2003/0143413 A1 Fig. 3 Patent Application Publication Jul. 31, 2003. Sheet 3 of 5 US 2003/0143413 A1 mid Patent Application Publication Jul. 31, 2003 Sheet 4 of 5 US 2003/0143413 A1 YMemorrOOOOL way www.scriptwrenna DODOO ODOOO OOOOO md OOOOO DDDDD DODOO . OOOOO 3DOOOO. mid Patent Application Publication Jul. 31, 2003. Sheet 5 of 5 US 2003/0143413 A1 US 2003/0143413 A1 Jul.
    [Show full text]
  • Inventors in the Dictionary of National Biography
    7KH3LWIDOOVRI3URVRSRJUDSK\,QYHQWRUVLQWKH'LFWLRQDU\ RI1DWLRQDO%LRJUDSK\ &KULVWLQH0DF/HRG$OHVVDQGUR1XYRODUL Technology and Culture, Volume 47, Number 4, October 2006, pp. 757-776 (Article) 3XEOLVKHGE\-RKQV+RSNLQV8QLYHUVLW\3UHVV DOI: 10.1353/tech.2006.0240 For additional information about this article http://muse.jhu.edu/journals/tech/summary/v047/47.4macleod.html Access provided by username 'mlcs' (3 Jun 2015 14:06 GMT) The Pitfalls of Prosopography Inventors in the Dictionary of National Biography CHRISTINE MACLEOD and ALESSANDRO NUVOLARI The Dictionary of National Biography was a triumph of Victorian literary engineering and private enterprise. Its original sixty-three volumes con- tained 29,120 entries.1 They were produced in “eighteen years of unremit- ting labour” between 1882 and 1900, and published at the formidable rate of one volume every three months (precisely).2 The Dictionary (hencefor- ward DNB, as it is affectionately known in Britain) was intended to provide “full, accurate, and concise biographies of all noteworthy inhabitants of the British Islands and the Colonies (exclusive of living persons) from the ear- liest historical period to the present time.”3 Christine MacLeod is senior lecturer in economic and social history at the University of Bristol. Alessandro Nuvolari is assistant professor in the economics of science and tech- nology at Eindhoven University of Technology. They thank Anna Guagnini, Johan Schot, Richard Langlois, Mark Curtoys, A. P. Woolrich, and Nicoletta Corrocher, as well as the editor and the three anonymous referees of T&C for their helpful comments on previ- ous drafts. The financial support of the Netherlands Organization for Scientific Re- search–British Council Partnership Programme in Science (grant number PPS 833) and of the Arts and Humanities Research Council (award number RL/AN11100/APN 17938) is gratefully acknowledged.
    [Show full text]
  • A Chronological History of Electrical Development from 600 B.C
    From the collection of the n z m o PreTinger JJibrary San Francisco, California 2006 / A CHRONOLOGICAL HISTORY OF ELECTRICAL DEVELOPMENT FROM 600 B.C. PRICE $2.00 NATIONAL ELECTRICAL MANUFACTURERS ASSOCIATION 155 EAST 44th STREET NEW YORK 17, N. Y. Copyright 1946 National Electrical Manufacturers Association Printed in U. S. A. Excerpts from this book may be used without permission PREFACE presenting this Electrical Chronology, the National Elec- JNtrical Manufacturers Association, which has undertaken its compilation, has exercised all possible care in obtaining the data included. Basic sources of information have been search- ed; where possible, those in a position to know have been con- sulted; the works of others, who had a part in developments referred to in this Chronology, and who are now deceased, have been examined. There may be some discrepancies as to dates and data because it has been impossible to obtain unchallenged record of the per- son to whom should go the credit. In cases where there are several claimants every effort has been made to list all of them. The National Electrical Manufacturers Association accepts no responsibility as being a party to supporting the claims of any person, persons or organizations who may disagree with any of the dates, data or any other information forming a part of the Chronology, and leaves it to the reader to decide for him- self on those matters which may be controversial. No compilation of this kind is ever entirely complete or final and is always subject to revisions and additions. It should be understood that the Chronology consists only of basic data from which have stemmed many other electrical developments and uses.
    [Show full text]
  • Joseph Saxton
    MEMOIR OP JOSEPH SAXTON. 1799-1873. BY JOSEPH HENRY. HEAD BEFOEB THB NATIONAL ACADEMY, OCT. 4,1874. 28T BIOGRAPHICAL MEMOIR OF JOSEPH SAXTON. MR. PRESIDENT AND GENTLEMEN OF THE ACADEMY :— AT the last session of the National Academy of Sciences I was appointed to prepare an account of the life and labors of our lamented associate, Joseph Saxton, whose death we have been called to mourn. From long acquaintance and friendly relations with the deceased, the discharge of the duty thus devolved upon me has been a labor of love, but had he been personally unknown to me, the preparation of the eulogy would have been none the less a sacred duty, which I was not at liberty on any account to neglect. It is an obligation we owe to the Academy and the world to cherish the memory of our departed associates; their reputation is a precious inheritance to the Academy which exalts its character and extends its usefulness. Man is a sympathetic and imitative being, and through these characteristics of his nature the memories of good men produce an important influence on posterity, and therefore should be cherished and perpetuated. Moreover, the certainty of having a just tribute paid to our memory after our departure is one of the most powerful inducements to purity of life and propriety of deportment. The object of the National Academy is the advancement of science, and no one is considered eligible for membership who has not made positive additions to the sum of human knowledge, or in other words, has not done something to entitle him to the appellation of scientific.
    [Show full text]
  • Background Information
    Background information Nuremberg, November 3, 2016 A powerful driving force for 150 years The discovery of the dynamo-electric principle has brought about greater changes to the way our society lives than practically any other scientific breakthrough. By inventing the dynamo machine, not only did Werner von Siemens help bring about the advent of electrical machinery, he was also instrumental in accelerating and facilitating industrial processes. Seen from the perspective of society, this completely changed accepted concepts of time and mobility. Werner von Siemens was consequently justified in the confidence he expressed in concluding his report to the Berlin Academy of Sciences in 1867 with the words: “Technology now has the means to generate electrical current of unlimited strength in an inexpensive and convenient way wherever mechanical energy is available.” The first dynamo machines were then also used for the generation of electricity for “light and for galvanic metallurgy and for small electromagnetic machines that get their power from large ones” (Werner von Siemens). 18 years later, Nikola Tesla and Galileo Ferraris independently discovered that alternating currents displaced in time generated a rotating magnetic field with the ability to move an armature. Based on this work, in 1889 the head engineer at AEG, Michail von Dolivo-Dobrowolski, developed the first usable asynchronous motor, whose principle still forms the basis of 85 percent of all practical drive applications today, according to the ZVEI. Siemens AG Wittelsbacherplatz 2 Communications 80333 Munich Head: Clarissa Haller Germany Seite 1/11 Siemens AG Background information Fig. 1: Structure of the dynamo machine This discovery paved the way for mechanizing heavy work such as rolling, drilling, milling and grinding in factory halls.
    [Show full text]
  • Landmarks of American History and Culture Workshops for School Teachers: America's Industrial Revolution at the Henry Ford
    National Endowment for the Humanities Landmarks of American History and Culture Workshops for School Teachers: America's Industrial Revolution at The Henry Ford Sample K-12 lesson plans from participant of 2010 America’s Industrial Revolution at The Henry Ford The story of America’s Industrial Revolution is an epic tale, full of heroes and heroines, villains and vagabonds,accomplishments and failures, sweated toil and elegant mechanisms, grand visions and unintended consequences. How did the United States evolve from a group of 18th century agricultural colonies clustered along the eastern seaboard into the world’s greatest industrial power? Why did this nation become the seedbed of so many important 19th century inventions and the birthplace of assembly-line mass production in the early 20th century? Who contributed? Who benefited? Who was left behind? At The Henry Ford in Dearborn, Michigan, school teachers from across the country explored this story with university scholars and museum curators during two week-long teacher workshops supported by the National Endowment for the Humanities. Workshop participants spent mornings discussing their passion for American history with distinguished university professors, mid-days on field trips to more than a dozen historic farms, mills and laboratories, and afternoons planning activities for their students. They developed methods for incorporating various senses and learning styles into new lesson plans that bring America’s Industrial Revolution out of the books and into living history. This
    [Show full text]
  • Induction Coils A
    7/25/2018 Induction Coil Induction Coils A. The Original Induction Coils The original induction coil was invented in 1836 by Nicholas Callan (1799-1864), a priest and the professor of natural philosophy at St. Patrick's College at Maynooth, County Kildare, Ireland. The basis for the coil was his large electromagnet with primary and secondary windings on the extremities of the U-shaped iron core. The primary circuit was interrupted (to get the required alternating current) by the mechanical Repeater that Callan designed. Callan's Great Induction Coil (left below) was left unfinished at Callan's death. The three secondary coils contain a total of 150,000 feet of fine iron wire. The primary coil is made of copper tape, wound around a core of iron wires. At the right below is the (incomplete) mechanism of interrupting the primary current. This apparatus, along with a similar one made by Callan which has only one secondary coil, is on display at the St. Patrick's College museum. The museum at St. Patrick's College contains parts of other early induction coils by Nicholas Callan. At the right are two long primary coils, and four toroidal secondary coils. The latter were insulated with a mixture of melted rosin and beeswax. Callan found that he could insulate 8000 ft of iron wire, 0.03 in. in diameter, per hour by passing it through this mixture and allowing it to harden on the wire, all in a continuous process. Independent of Callan, the American electrical inventor Charles Grafton Page (1812-1868) developed an induction coil in 1836.
    [Show full text]
  • Origin of the Electric Motor
    Origin of the Electric Motor JOSEPH C. MIGHALOWICZ MEMBER AIEE HE DAY that man Had it not been for the efforts of men like 1821—Michael Faraday dem- T molded the first wheel Davenport, De Jacobi, and Page, the benefits onstrated for the first time the from the sledlike skids of his of the electric motor would not be enjoyed possibility of motion by electro- magnetic means with the move- primitive wagon should be today. It is the purpose of this article to trace ment of a magnetic needle in a one of great commemoration, briefly the early history of the science of electro- field of force. had not its identity been lost motion and, in particular, to bring to light and 1829—-Joseph Henry, a teacher in the passing of time. Not to honor the inventor of the electric motor. of physics at the Albany Academy unlike the wheel and prob- in New York, constructed an elec- ably second only to the wheel, tromagnetic oscillating motor but considered it only a "philosophical the electric motor has been a toy." great benefactor to man and its history, too, slowly is 1833—Joseph Saxton, an American inventor, exhibited a magneto- being forgotten. Today, we hear very little, if anything, about Thomas Figure 1. Thomas Davenport, the blacksmith who invented the electric Davenport, inven- motor; or about De Jacobi, who propelled the first boat tor of the electric by means of an electric motor; or of Charles Page who motor successfully carried passengers on the first practical electric railway. Had it not been for the efforts of these men and others like them, the benefits of the electric motor probably would not be enjoyed today.
    [Show full text]
  • Tesla Files His Patents for the Electric Motor
    NUMBERS DON’T LIE_BY VACLAV SMIL OPINION corresponding lecture at the American Institute of Electrical Engineers, one of IEEE’s predecessor societies. However, it was Tesla, helped with generous financ- ing from U.S. investors, who designed not only the AC induction motors but also the requisite AC transformers and dis- tribution system. The two basic patents for his polyphase motor were granted 130 years ago this month. He filed some three dozen more by 1891. In a polyphase motor, each electromag- netic pole in the stator—the stationary housing—has multiple windings, each of which carries alternating current that’s out of phase with current in the other windings. The differing phases induce a current flow that turns the rotor. George Westinghouse acquired Tesla’s AC patents in July 1888. A year later Westinghouse Co. began selling the world’s first small electrical appliance, a fan powered by a 125-watt AC motor. Tesla’s first patent was for a two-phase MAY 1888: motor; modern households now rely on many small, single-phase electric TESLA FILES HIS PATENTS motors. The larger, more efficient three- phase machines are common in indus- trial applications. Mikhail Osipovich FOR THE ELECTRIC MOTOR Dolivo-Dobrovolsky, a Russian engi- neer working as the chief electrician for Germany’s AEG, built the first three- ELECTRICAL DEVICES ADVANCED by leaps and bounds in the 1880s, phase induction motor in 1889. which saw the first commercial generation in centralized power plants, Today, some 12 billion small, non- the first durable lightbulbs, the first transformers, and the first (limited) industrial motors are sold every year, urban grids.
    [Show full text]