Almost all of our electrical systems use 3 phase AC electricity, but how does it work, why was it invented, and who invented it? Ready for the surprising but complex and story as well as the answer to why some countries use 50 Hz and some use 60 Hz and one country uses both?
In order to tell you the story of 3-phase and why it is so complicated, I feel like I need to take a step back and start with a bit about Westinghouse and 2-phase generators and motors which arguably begins in April 1888. At this time Westinghouse had been electrifying cities with alternating current (AC) for 2 years, but Edison had only really been upset about it for around 4 months, when a syndicate cornered the copper market which increased the cost of DC (which used about 3 times the copper) in comparison with AC. However, Westinghouse had trouble with his system that had nothing to do with Edison’s ire; he didn’t have a way to convert electricity that went back and forth to motion that went in a circle for meters and electric motors. Westinghouse was first primarily concerned with a meter, as he knew that if he didn’t have a meter to measure how much power he was distributing, he would have to charge a flat rate, which incentivizes customers to use as much light as possible. Luckily, in April of 1888, an employee named Shallenberger dropped a spring near two pieces of equipment and found that the dropped spring started to spin. Within a month Shallenberger had a working meter and by August they had a system on the market. The meter which operated at 133 Hz was very popular and sold 120,000 units in just 10 years. Now Westinghouse had a meter, but he was still looking for a motor, or something that could do industrial work that was powered by alternating current.
A few weeks after Shallenberger dropped that spring, Westinghouse heard from an employee that the employee’s former professor, an Italian scientist named Galileo Ferraris had created a new type of AC electricity and a corresponding AC motor. Ferraris’ idea required a special generator which generates electricity with two separate sets of coils at 90 degrees to each other. These coils are identical and electrified by the same electromagnet so they have identical current induced in them with the same frequency. In fact, the only difference is the timing of their maximum value, or their phase. Because the two sets of coils have two different phases, this kind of generator is now called a 2-phase generator. (Note that 2-phase generators often have 4 sets of coils, that is because if the coils are at 180 degrees from each other, their wires can be connected as when current is induced in one coil it is induced the other direction in the opposite coil.) In a 2-phase motor, the AC currents are attached at 90 degrees around the object that they were attempting to rotate, called the rotor. The AC current in the coils then induces a current in the rotor and the force between that alternating current from the sets of wires and the induced current in the rotor is what causes the rotor to spin. Ferraris didn’t patent his idea as he didn’t think it would work on an industrial scale, but Westinghouse paid him $1,000 for it anyway, even though Ferraris offered it for free.
At the same time, May, 1888 Westinghouse heard that a 32-year-old Serbian inventor named Nikola Tesla was demonstrating to the American Institute of Electrical Engineers a 2-phase AC motor and generator where the motor was powerful and could be used in industry. According to Tesla, this generator and motor were exactly the same as Ferraris’ 2 phase concept. As Tesla admitted a few months later when he was called on this: “Professor Ferraris not only came independently to the same theoretical results, but in a manner identical almost to the smallest detail.” Nevertheless, Tesla owned the American patent for the 2-phase generator and motor and, despite the fact that Westinghouse’s lawyer found the purchase price to be “monstrous,” Westinghouse felt that, “the Westinghouse Electric Company cannot afford to have others own the patents that are necessary to enable it to make motors to work on the alternating current system.” Therefore, on October 1888, George Westinghouse paid a whopping $170,000 for the motor (equivalent of around $5 million today) with a further $2.50 per horsepower for motors sold in perpetuity. Westinghouse was a very generous man and in 1900 Tesla stated, “Had other industrial firms and manufacturers been as just and liberal as Mr. Westinghouse, I would have had many more of my inventions in use than I now have.” However, despite Westinghouse pouring a further $300,000 into making Tesla’s motor work on an industrial scale, Westinghouse’s team could not get it to work, partially because Tesla’s motor was designed at 60 Hz and Westinghouse wanted it to be at 133 Hz to match Shallenberger’s meter. In April of 1890, Edison’s spy wrote him a gleeful note: “Mr. Westinghouse has ..[only] one alternating current experiment, which is a failure, and Mr. Westinghouse has quarreled with Mr. Tesla [misspelled Mr. Tessler] who invented the alternate current motor.” Despite not having a working industrial motor and being in a PR “battle” with Edison, Westinghouse’s company was doing very well: between 1886 and 1890, Westinghouse’s company sales went from $150,000 a year to more than $4 million a year!
Then, on November 15, 1890, a bank in England collapsed, and the economy in England and America went with it. Westinghouse had borrowed heavily to fulfill all his new orders, and his business was now on the verge of collapse. The bankers agreed to fund him but wanted another person as manager as, “Mr. Westinghouse wastes so much on experimentation, and pays so liberally for whatever he wishes in the way of service and patent rights.” Westinghouse found funding elsewhere, but was trying to be more economical, so he stopped all research on Tesla’s motor (although he still had to pay $15,000 to Tesla every year as a minimum payment).
However, even though Westinghouse’s research into making a multi-phase motor was stalled, there were others making progress on it. The most important was a 26-year-old Russian/Polish man working for the German company AEG named Mikhail Dolivo-Dobrovolsky.
In late 1888, a few months after Tesla became famous for his 2-phase system, Dolivo-Dobrovolsky decided that, “Tesla’s arrangement, with two entirely independent currents differing by 90 deg. in their phases, was not particularly advantageous,” as the field around the rotor would fluctuate by 40%. Dobrovolsky mathematically determined that three phases lowered the fluctuations to 15%, and began building generators and motors that had three separate sets of coils. This was when Dolivo-Dobrovolsky came to a remarkable conclusion that 3-phase wasn’t just better for motors, it was a new way of transferring electricity with only three wires, not six. This trick is only possible because if you connect three waves that are all 120 degrees apart at any point, the total will add up to zero. In this way, you can basically ground three of the six wires, and only need 3 live wires for transmitting electricity, and, when you reach the end of your line, you just combine the 3 live wires to the ground and do not need a return. This is very important, because with transmitting electricity, especially over long distances, the problem is always how to lower costs, which usually means lowering the amount of copper wire needed. With 3-phase power, you can reduce the amount of wire needed for transmission by 50% and you can still use all three phases to power high-voltage 3-phase motors.
Not only that but in August of 1889, Dolivo-Dobrovolsky also patented two types of 3-phase transformers: called delta and star (or why) for the shapes that they make. With these transformers, the three phases can be safely transformed to high voltages and low current for long distance transmission without much loss and then transformed back to lower voltages to be safely used. You might be wondering how Dolivo-Dobrovolsky managed to light lightbulbs with a single live wire, and the answer is he didn’t. Instead he used a single live wire to the bulbs with a “return” of a neutral wire, which is a wire that is created so that, if the 3 phases are in balance, there is no current in them but they can still complete the circuit.
Not only that, but Dobrovolsky also realized that his 3-phase motor was not very efficient as it induced circular currents called eddy currents in the rotor (the part that spun) which worked against the motion of the rotor. To reduce the amount of eddy currents, Dobrovolsky started to put a series of parallel slits in the rotor, which he patented in 1889. With the slits these rotors look like large cages and in 1894, the English scientist Silvanus Thomson called it a “sort of squirrel cage” as it looked large enough to hold a squirrel I guess, and the name stuck. Squirrel-cage motors are a mainstay in modern engineering and in 2017, an engineering textbook stated that Dolivo-Dobrovolsky’s design from the 1890s remains, “virtually unchanged for more than 100 years of their existence.”
In 1890, Dolivo-Dobrovolsky’s transmission system and motor impressed an intense looking man named Oskar von Miller who was the technical director of an upcoming Frankfurt Electrical Exposition. Miller had initially hoped to use high voltage DC powered from a waterfall, but the closest waterfall with a nice cement factory next to it with a turbine that they could use was in Lauffen, Germany, a full 175 km away. At first, Miller went to a Swiss engineer named Charles Brown whose company had been experimenting with long distance DC from hydroelectric plants, but, after some deliberations, Miller decided to work with the exciting new 3-phase transmission, and, so, Miller brokered an unusual cooperation between Brown’s company, Dolivo-Dobrovolsky’s company, the German government and the cement factory to make this technological advance.
Dobrovolsky and Brown then created 3-phase electricity with the generator powered by a waterfall in Lauffen, then used a star transformer to step up the voltage from 55 volts to the startlingly high (at the time) 8,500 volts, and then used only three live wires at that high voltage to the town of Frankfurt. This high voltage was needed, because they needed to use the thinnest wire possible. Shoot, even with their super thin 5 mm thick wires, they still used over 60 tons of copper! Dobrovolsky and Brown then used another star transformer to step down the voltage to around 65 volts where they used it to electrify sets of lights, as well as a 3-phase 100-hp motor that powered an artificial waterfall.
This system, that many scientists and engineers had previously assumed would not work over long distances, made that impressive distance with 74% of its power intact and was heralded as, “nothing short of magnificent.” An account in The Electrical Engineer Magazine beamed: “I do not think that I am guilty of exaggeration in expressing an opinion that the Lauffen-Frankfort transmission is the most difficult and most momentous experiment made in technical electricity since that mysterious natural force … has been made serviceable to mankind.” This was the first electrical system that in any way resembles modern electrical distribution, and we continue to use three phase, delta transformers, and star or why transformers to this very day. However, don’t be confused by the three plugs in household plugs to think that we are getting 3-phases in each plug. In reality, most household plugs actually only gets ONE live wire (the other two plugs are the neutral and the ground wire, a wire connected to a large metal stick in the ground).
However, Dolivo-Dobrovolsky was not particularly adept at explaining the advantages of his system, and many people became confused about the difference between 2 phase and 3 phase which all started to be called “polyphase”: a name it retains to this very day (In addition, unknown to Dolivo-Dobrovolsky, his collaborator on the project, Charles Brown, became jealous of the attention that Dolivo-Dobrovolsky was gaining for 3-phase. In October of 1891, Brown wrote a letter to the editor of “The Electrical World” magazine stating that, “the adoption of the three-phase current only increased the difficulties to be met” and that all of the real “constructive improvements” demonstrated at the Frankford exhibition were “almost without exemption” due to him! In addition, Brown claimed that “the three-phase current as applied at Frankfort is due to the labors of Mr. Tesla, and will be found clearly specified in his patents.” Now you might be wondering what Brown was talking about with that last comment, let me explain. See it turns out that back in 1888, Tesla not only patented a 2-phase generator and motor but also a 3-phase motor. If D Dolivo-Dobrovolsky had known about Tesla’s 3-phase motor, he might have emphasized that Tesla’s had 6 wires not 3, and the advantages of the 3-wire 3-phase transmission system, but he didn’t and instead focused on the advantages of 3-phases for the motor over 2-phases, which weakened his claim. As Dolivo-Dobrovolsky did not speak English and Brown did, and the system was so complex, many scientists started to believe that Tesla invented 3-phase transmission instead of Dolivo-Dobrovolsky.
All of that might have been sorted out if on May 20th, 1891, about a week after the fair opened, Tesla’s backers pushed him to give his first talk on his newest device – the Tesla coil. The Tesla coil was an instant success on a global scale. 3-phase could reduce the wires by 50%, but Tesla coils could light a bulb with no wires if held near the coil! The world went into, basically, a Tesla mania, and as an article in the Electrical Engineer Magazine put it, “No man in our age has achieved such a universal scientific reputation in a single stride as this gifted young electrical engineer.”
It was at this pivotal time that George Westinghouse started to re-invest into making Tesla’s 2-phase motor work on an industrial scale. Part of the motivation was that one of his engineers convinced him that 60 Hz would travel longer distances with less loss than 133 Hz, and that another engineer named Benjamin Lamme claimed he could improve Tesla’s motor’s windings and make them work for industry. With an agreement with Tesla and his backers (who owned 54% of the patent), Westinghouse was allowed to drop any payments on horsepower in the motors and, in late 1891, Benjamin Lamme was finally allowed to build his two-phaseAC motor and succeeded in creating a 2-phase motor that was industry ready by the beginning of 1892, which, according to Lamme, was the first induction motor made at the Westinghouse Company, “which bears any close resemblance to the modern type.”
As the 1893 World’s Fair in Chicago’s opening approached, Westinghouse held a meeting on the promotion of their new “Tesla” motor and Benjamin Lamme suggested that they should make what he called a “fad” out of polyphase generators, “so that everybody would buy them, the motor question would soon settle itself.” Years later Lamme recalled that, “instructions were given immediately to get out a standard line of polyphase generators and push them on any and every occasion.” However, Westinghouse realized that it would be difficult to promote polyphase generators at the fair as they didn’t have enough industrial 2-phase generators and transformers in stock and they didn’t have enough time to build them. According to Lamme, Westinghouse suggested using two separate single-phase generators that were staggered 90 degrees apart as “a step towards a coming polyphase supply system.” By this time, Westinghouse could clearly see how promoting the connection between his name and Tesla’s would only help his business. For that reason, Westinghouse created the entrance to the electrical pavilion at the world’s fair with the words “Westinghouse Electric & Manufacturing Co. [with] Tesla Polyphase System,” and invited Tesla to give a demonstration in his area of the pavilion and for the next 10 years or so pushed his connection to Tesla at every turn.
Meanwhile, in 1892, the year before the fair, Edison’s General Electric had merged with another company and Thomas Edison was fired and his company dropped his name and became plain old General Electric or GE. Freed from Edison’s prejudice against AC, General Electric went straight from almost all DC power to being a leader in 3-phase AC! According to Lamme, who became the chief engineer at Westinghouse Electric: “There were two polyphase schools, so to speak, namely the two-phase and the three-phase. The Westinghouse Company was known as the advocate of the two-phase polyphase systems, although it built both; whereas the General Electric Company was considered as favoring three-phase, although it also built both.” 
After the fair, Westinghouse and his lawyers began to win the lawsuits for 2-phase and 3-phase power. In April 1896, Westinghouse paid Tesla $216,600 for all of his multiphase patents in a contract to be shared with GE which basically left both companies free to do whatever multiphase systems they wanted to, and gave both companies (who controlled the electricity market) a huge incentive to talk up Tesla’s contribution and to downplay Dolivo-Dobrovolsky’s.
Meanwhile, Dolivo-Dobrovolsky continued to work at AEG as their head engineer and helped his company become the leader of electrical distribution in Europe and Asia and Africa. As Dobrovolsky experimentally knew that higher frequency caused more loss, at first, he used 40 Hz, however, he felt that it blinked unpleasantly, so he upped it to 50 Hz, where it remains to this day. Tesla on the other hand, insisted on 60 Hz, where it remains in the United States and in countries originally supplied electricity by GE or Westinghouse. One of the strangest examples is in the country of Japan, where Dolivo-Dobrovolsky’s company (AEG) provided the electricity for Tokyo in 1895 at 50 Hz, and GE provided the electricity for Osaka in 1896 at 60 Hz, and, now the entire country is split in two: half at 50 Hz and half at 60 Hz!
In 1914, World War I began, and Dobrovolsky wisely decided that Germany wasn’t a safe place to be for a Russian man and spent much of the war in Switzerland, where he dropped his Russian citizenship for a Swiss one. He returned to Germany in 1918, when Russia ended its participation in World War 1 (as they were busy with the Russian Revolution). However, by then Dolivo-Dobrovolsky was having heart issues and he died from heart problems in November, 1919 at the age of 56. The Germans, in the middle of losing World War I, weren’t particularly interested in honoring the accomplishments of a Russian/Polish man who had abandoned them in their hour of need, and the Russians were pretty busy with revolution to want to honor a man who had mostly accomplished things in Germany, had revoked his Russian citizenship and hadn’t participated in their revolution. As Americans were wholly invested in the story that Tesla had invented all of polyphase electricity (as Westinghouse and GE owned Tesla’s patents), his influence and life story were mostly hidden especially considering his considerable influence on our electric world.
In conclusion, if you ask who invented the first 3-phase motor and generator, the answer is pretty clearly Nikola Tesla who patented a 3-phase motor and generator in 1888, but if you ask who was the first to create 3-wire 3-phase electric generation, distribution, transistors and power, as well as the squirrel cage motor and more the answer is different: Mikhail Dolivo-Dobrovolsky. As Dolivo-Dobrovolsky wrote in 1891, “Though the scientific value of the discoveries of Professor Ferraris and Mr. Tesla must not be lessened, yet the merit of the practical working out and execution of the rotary-current [3 phase] system is undoubtably due to [my company]… that brought the whole system to such a pitch of perfection.”
If you are wondering why higher frequencies have higher loses in the lines, and also wondering how GE went from an almost all DC company to a leader of 3-phase electricity, the answer is another scientist who isn’t well known as he should be. One of my favorites: the charismatic and quirky, “Wizard of Schenectady” Charles Stienmetz. And his story is next time at the lightning tamers.
If you are interested in what inspired Ferraris and Tesla to invent the 2-phase motor and generator, which really was a major advance in engineering, I have found how Ferraris was inspired by optics and Tesla was inspired by something called Arago’s wheel. If you want to know more, I have made a video about it, and you can see it and read the script if you join my mailing list. Link below. As an extra incentive, you will be first in line to know when my new book will be out, due Spring 2022. If you are feeling generous, you can join my Patreon and get thanked (thank you Patrons) as well as videos early and other perks, like sneak peaks of my book. I realize that I have said some controversial things, so I added my references below, and I encourage you to double or triple check my work. This is confusing stuff and I am a 1-woman show, I do all the research, write the script, film and edit it so I could have easily made mistakes and I would like to correct them if I do.
 the Story about Shallenberger can be read in Alfred, R “Aug 14, 1888: I Sing the Meter Electric” Wired Magazine (Aug 14, 2008)
 The account that Ferraris did not ask for any money is from Thomson, S Polyphase Electric Currents and Alternate-current Motors (1900)p. 444
 “Professor Ferraris not only came independently…” from “Mr. Nikola Tesla on Alternating Current Motors” The Telegraphic Journal and Electrical Review vol. xxiv(June 7, 1889) p. 648
 Westinghouse wanting the contract with Tesla despite his lawyers finding the cost “monsterous” is from Carlson, W Tesla: Inventor of the Electrical Age (2013) p.113
 $170,000 in 1888 is $4,949.487 in 2021 according to the website in2013dollars.com
 “….as just and liberal as Mr. Westinghouse…” from Tesla, N “Tesla’s Tribute to Westinghouse,” The Age of Steel LXXXVIII, no. 10(September 1900), 9.
 Stanley stated that Westinghouse had poured $300,000 into Tesla coils is from William Stanley “The Induction Motor” Engineering News (Oct 2, 1902) vol. XLVIII No. 14p. 279
 Frank Sprague to Sprague Executive Board (leaked to Edison) (April 29, 1890) Edison Papers Digital Edition [X120CBN]
 Westinghouse’s company sales is from Jonnes, J Empires of Light (2003) p. 223
 “Mr. Westinghouse wastes so much on experimentation…” from Leupp, F George Westinghouse: His Life and Achievements (1919) p. 159
 Westinghouse stopped funding Tesla’s motor is from Skrabec, Q George Westinghouse: Gentle Genius (2007) p. 130
 I got many details about Dolivo-Dobrovolsky from translating “Mikhail Dolivo-Dobrowolsky (1862-1919)” [in Russian] Vavilov, S People of Russian Science: Essays on Outstanding Figures of Natural Science [Люди русской науки: Очерки о выдающихся деятелях есте- ствознания и техники] (1948)
 “Tesla’s arrangement…was not particularly advantageous,” is from Dolivo-Dobrowosky, M “Transmission of power by rotary-phase alternate currents”, Electrical Engineer (London), vol. 7, p 369, (April 10, 1891)
 The date of Dolivo-Dobrovolsky’s transformer patents is from “The invention of the electric motor 1856-1893” Elektrotechnisches Institut (ETI) https://www.eti.kit.edu/english/1390.php
 Dolio-Dobrovolsky created squirrel cage is in “Mikhail Dolivo-Dobrowolsky (1862-1919)” [in Russian] Vavilov, S People of Russian Science: Essays on Outstanding Figures of Natural Science [Люди русской науки: Очерки о выдающихся деятелях есте- ствознания и техники] (1948) also Thompson, S Polyphase Electric Currents (1900) p. 173
“sort of squirrel cage” from Thomson, S Elementary Lessons in Electricity and Magnetism, (1894) p. 507
 “virtually unchanged up to now” Ushakov, V “Electrical Power Engineering” (2017) p. 16
 “Miller decided to work with the exciting new 3-phase transmission” from Allerhand, A “The Earliest Years of Three-Phase Power” Proceedings of the IEEE vol. 108 (Jan, 2020) p. 215-6
 Copper needed is from ibid
 Transformers and voltages used is from Herausgegben vom Vorstand der Ausstellung Offizieller Bericht über die Internationale elektrotechnische Ausstellung in Frankfurt am Main, 1891 (1894) p. 324
 “nothing short of magnificent” is from Lightning: Volume 1 (April 28, 1892) p. 509
 “…the Lauffen-Frankfort transmission is the most difficult …” from “The Transmission of Power at Frankfort” The Electrical Engineer (Sept 18, 1891) p. 286
 “the adoption of the three-phase current only increased” from Brown, C “Reasons for the Use of the Three-Phase Current in the Lauffen-Frankfort Transmission” The Electrical World (Nov 7, 1891) vol. XVIII No. 19 p. 345
 “Tesla not only patented a 2-phase generator and motor but also a 3-phase motor” Nikola Tesla patent US 382,280 “Electrical Transmission of Power” (May 1, 1888)
 “No man in our age has achieved such a universal scientific reputation …” “Mr. Tesla’s Experiments” (April 6, 1892) Electrical Engineer vol 13-14, p. 350
 According to Lamme, B “The Story of the Induction Motor” (March 1921) Electrical Engineering (New York) vol. XL p. 205 “Mr. L. B. Stillwell, who was giving this matter active attention… recommended in favor of 60 cycles, and, in 1891, this was making some progress”
 Tesla’s patent was co-owned by supporters Alfred Brown and Charles Peck, according to Carlson, B Tesla: Inventor of the Electric Age p. 130 “Since they had shrewdly handled the business negotiations and assumed all of the financial risk in developing the motors, Tesla gave Peck and Brown five-ninths of the proceeds from the deal while retaining four-ninths for himself”
 The 2-phase motor at Westinghouse in 1892, “which bears any close resemblance to the modern type.”Lamme, B Benjamin Garver Lamme, Electrical Engineer, An Autobiography (1926) p. 61
 “instructions were given immediately to get out a standard line of polyphase generators” Lamme, B “The Story of the Induction Motor” (March 1921) Electrical Engineering (New York) vol. XL p. 212
 Westinghouse suggested using 2 single phase generators according to Lamme, B Benjamin Garver Lamme, Electrical Engineer, An Autobiography (1926) p. 61
 “There were two polyphase schools, so to speak…” Davis, L Fleet Fire: Thomas Edison and the Pioneers of the Electrical Revolution (2012)
 “Westinghouse paid Tesla $216,600” “Annual Report of the Board of Directors of the Westinghouse Electric” Electricity (June 30, 1897) p. 387
 “(AEG) provided the electricity for Tokyo in 1895 at 50 Hz, and GE provided the electricity for Osaka in 1896 at 60 Hz“ Gordenker, A “Japan’s incompatible power grids” Japan Times vol. 19 (July, 2011) p. 9
 “In 1914, World War I began, and Dobrovolsky wisely decided that Germany wasn’t a safe place to be for a Russian man and spent much of the war in Switzerland, where he dropped his Russian citizenship for a Swiss one.” According to “Mikhail Dolivo-Dobrowolsky (1862-1919)” Vavilov, S People of Russian Science: Essays on Outstanding Figures of Natural Science [in Russian] Люди русской науки: Очерки о выдающихся деятелях есте- ствознания и техники (1948)
 “Though the scientific value of the discoveries of Professor Ferraris and Mr. Tesla…” Dolivo-Dobrowolsky “Transmission of Power by Rotary-Phase Alternative Currents” The Electrical Engineer (April 3, 1891) p. 336
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