The induction motor is one of the most important inventions in modern history. It turned the wheels of progress at a new speed and officially kicked off the second industrial revolution by drastically improving energy generation efficiency and making long distance distribution of electricity possible. Today, not only do these turn on the lights in your home but also power any mechanical gadget you take for granted from vacuum cleaners to electric toothbrushes to that classy Tesla Motors Model S.

 One of the original Tesla Electric Motors from 1888 which is today the main power of for industry and household appliances. Credit: Wkimedia Commons

One of the original Tesla Electric Motors from 1888 which to this day is the main power generator for industry and household appliances. Credit: Wkimedia Commons

The first induction motor was invented by the famed Nikola Tesla in 1887 at his workshop on 89 Liberty Street, New York. This gifted inventor is said to have had a vision of his A-C motor one sunny day in Budapest, 1882, while reciting stanzas from Goethe’s Faust.

“At that age, I knew entire books by heart, word for word. One of these was Goethe’s ‘Faust’. The sun was just setting and reminded me of the glorious passage, ‘Sie ruckt und weicht, der Tag ist uberlebt, Dort eilt sie hin und fordert neues Leben. Oh, da kein Flugel mich vom Boden hebt Ihr nach und immer nach zu streben! Ein schöner Traum indessen sie entweicht, Ach, au des Geistes Flügeln wird so leicht Kein körperlicher Flügel sich gesellen!’ As I uttered these inspiring words the idea came like a flash of lightening and in an instant the truth was revealed. I drew with a stick on the sand, the diagram shown six years later in my address before the American Institute of Electrical Engineers, and my companion understood them perfectly.

The images I saw were wonderfully sharp and clear and had the solidity of metal and stone, so much so that I told him, ‘See my motor here; watch me reverse it.’ I cannot begin to describe my emotions. Pygmalion seeing his statue come to life could not have been more deeply moved. A thousand secrets of nature which I might have stumbled upon accidentally, I would have given for that one which I had wrested from her against all odds and at the peril of my existence…”

In the summer of 1883, while in Paris, Tesla built his first actual induction motor and saw it run. Tesla sailed for America in 1884, arriving in New York, with four cents in his pocket, a few of his own poems, and calculations for a flying machine. After a few odd jobs, he god employed by Thomas Edison who tasked him with improving the dynamo for his DC motor. Neither Edison, nor Edison’s investors, were interested in Tesla’s plans for alternative current.

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How a DC motor works

In a direct current motor, a magnet that supplies a magnetic field is fixed in place and forms the outside, static part of the motor. This is called the stator. A coil of wire is suspended between the poles of the magnet and hooked to a direct current power source, like a battery. The current running through the wire produces a temporary magnetic field (it’s an electromagnet), which repels the field from the permanent magnetic causing the wire to flip over.

Normally, the wire would stop over one turn and flip back again, but using a commutator the current can be reversed every time the wire flips. This way, the wire can keep rotating in the same direction for as long as the current keep flowing.

The DC engine was conceived by Michael Faraday in the 1820s, and turned into a practical invention a decade later by William Sturgeon. 

After a fight with the American inventor, Tesla left Edison’s lab and partnered with George Westinghouse in 1888 to whom he sold the patent for Tesla’s polyphase alternating current technology. Their partnership turned to gold when Westinghouse won the contract to supply the Chicago World’s Fair of 1893 with electricity.

How an AC motor works

Alternative current reverses its direction about times a second (~50 Hz), so use an electric motor you need a different design from the DC motor.

In an AC motor, the stator is comprised of a ring of electromagnets which produce a rotating magnetic field. Unlike a DC motor where the power is sent to the inner rotor, in an AC motor the power is coupled to these electromagnets to induce the field. The brilliant trick lies in energizing the electromagnets at a time, in pairs. When one pair is fully active, the other is completely shut down.

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When the coils are energized, they produce a magnetic field which induces an electric current in the rotor, which is an electrical conductor, per Faraday’s law. The new current produces its own magnetic field which tries to oppose the field that caused it, per Lenz’s law. This game of catch between the two magnetic fields is what ultimately turns the rotor.

Then, in 1885, Westinghouse Electric & Manufacturing Company and General Electric Company were tasked with harnessing the power of Niagara Falls with electricity, using Tesla’s technology. Despite Edison’s propaganda aimed at discrediting Tesla as an inventor and alternative current as a viable tech, like public demonstrations in which animals were brutally electrocuted with AC, Tesla’s designs followed the natural course of progress. As it traveled through transmission lines, the accumulated resistance in the wires greatly reduced the electrical power supplied by DC.  AC, on the other hand, did not suffer the same loss and was able to travel great distances with little loss of potential. Alternative current can also react with transformers to increase or decrease voltage, so electricity could be made at high power at generating stations then reduced right before local distribution.

Once in the 20th century, electrical power distribution witnessed a massive expansion all over the world. In the first decade of the century, for instance, a generating unit with a capacity of 25,000 kilowatts with pressures up to 200-300 pounds per square inch at 400°-500° F was considered large. In 1930, though, the largest unit in the United States had a capacity of 208,00 kilowatts, with pressures of 1,200 pounds per square inch. Driven by the economy of scale, the price per kilowatt-hour of electricity dramatically plunged which eventually helped electrify the whole nation. With so much energy at our disposal all of a sudden, the world was ready to bloom technologically.





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