Mikhail Dolivo-Dobrowolsky was born as the son of the Russian civil servant and landowner of Polish descent Josif Florovich Dolivo-Dobrowolski and Olga Mikhailovna Jewreinova from an old Russian noble family in Gatchina near Saint Petersburg. He spent his school days in Odessa, where his father was transferred in 1872. After secondary school he went to the Riga Polytechnic at the age of 16. At the end of the 1870s, after the murder of Tsar Alexander II, a wave of repression broke out, with which all progressively oriented students were expelled from their university, which was equivalent to a study ban in all of Russia. Among them was Dolivo-Dobrowolsky. After his forced exmatriculation in Riga in 1881, he left his homeland in 1883 and went to Germany. He studied electrical engineering at the Department of Electrical Engineering and Information Technology of the Technische Hochschule Darmstadt in Germany from 1883 to 1884. From 1885 to 1887, he became one of Eramus Kittler's first assistants. There he published several smaller publications and was in close contact with Carl Hering, a mechanical engineer from the USA and Kittler's first assistant. After the inventions, Dolivo-Dobrowolsky continued his research in the field of heavy current technology, inventing the phase meter in 1892 and the ferrodynamic wattmeter in 1909. He published papers and gave numerous lectures. From 1903 to 1907 he devoted himself to scientific work in Lausanne, where he acquired Swiss citizenship with his entire family in 1906. After his return to Berlin, he continued his work at AEG and became Technical Director of the apparatus factory in 1909. On 24 October 1911, he received an honorary doctorate from the TH Darmstadt, whose Dolivo building bears his name today. During his life he obtained over 60 patents. In 1919, Dolivo-Dobrowolski died of a severe heart condition at the academic hospital in Heidelberg. He was buried at the forest cemetery of Darmstadt, where his grave - located very close to the memorial of his teacher Erasmus Kittler - can still be visited today. In the city centre of Darmstadt in 1969 a street was named after Dr.-Ing. E. h. Michael Dolivo-Dobrowolsky, the Dolivostraße.
Invention of the three-phase system
In 1887, AEG Director General Emil Rathenau offered him a position, whereupon Dolivo-Dobrowolsky remained associated with the company until the end of his life. At the AEG, Dolivo-Dobrowolsky initially made an effort to further perfect direct current technology. After all, AEG's origins lay in an Edison subsidiary, and Edison, like Siemens, relied entirely on direct current. At that time, alternating current gradually attracted the attention of technicians, and engineers from Ganz Works in Budapest had designed the first transformer in today's sense in 1885. However, AC technology required further equipment, especially reliable and self-starting motors; AC theory was also still underdeveloped. Before Dolivo-Dobrowolsky, the Italian Galileo Ferraris drew attention to alternating current. Ferraris experimented with two alternating currents shifted by 90°, with which he operated specially designed motors. However, he believed that the maximum efficiency was 50 %. Independently of this, in 1887 Nikola Tesla designed a synchronous motor for two-phase alternating current, which was to introduce the two-phase alternating current network in America. Nikola Tesla already dealt with the subject in 1882 and developed a system in a very short time, which was protected by extensive patents. It comprised both motors and generators with multi-phase, preferably two-phase alternating currents. Regardless of these events, a forward-looking solution was found at AEG in 1888. Dolivo-Dobrowolsky worked with chained three-phase alternating current and introduced the term three-phase current. The associated asynchronous motor invented by him was the first functional solution. However, the asynchronous motor with squirrel-cage rotor had the problem of delivering only low torque at low speeds, such as when starting up. The solution was the slip ring motor, a variation of the asynchronous motor in which the short circuit of the rotor is opened and guided to the outside via sliprings. By connecting various external resistors, Dolivo-Dobrowolsky was able to introduce an asynchronous motor with high starting torque in 1891. At the beginning of 1889, the first AEG three-phase motors were in operation, and in the following year they already produced 2 to 3 horsepower. Dolivo-Dobrowolsky paid attention to well distributed windings, a low dispersion of the lines of force and as uniform a force field as possible and achieved a satisfactory result. In 1891, he also developed the first Delta-wye transformer for this purpose.
At AEG and the Swiss cooperation partner Maschinenfabrik Oerlikon, all components for a three-phase network were available, but until now they had only been in trial operation. At this time, Oskar von Miller made the extremely daring proposal to present the three-phase current transmission system Lauffen-Frankfurt at the International Electrotechnical Exhibition planned for 1891 in Frankfurt at the MFO, where Dolivo-Dobrowolsky and his chief electrician partner Charles E. L. Brown realized the project: A 300 HP three-phase AC generator of the MFO was to be driven by the water turbine of the cement plant in Lauffen am Neckar, generating a voltage of about 50 V and 40 Hz, transforming it up to 15 kV and then transmitting it via 175 km of overhead line to Frankfurt and transforming it down again to supply a 100 HP asynchronous motor and several small three-phase motors as well as about 1000 incandescent lamps. The power output of the motors, which had previously been in test operation, was still only 2 to 3 hp. Nevertheless, the plant was put into operation on the evening of 24 August 1891, and a test committee determined that 75 % of the energy generated in Lauffen arrived in Frankfurt. This proved that, on the one hand, alternating current was profitable for a large-scale public electricity supply and, on the other hand, that the three-phase components were now of the same quality as those of direct current technology. The image-boosting effect of the demonstration at the World Expo finally led to the breakthrough of three-phase AC technology. At Siemens and Edison, however, AC technology only slowly gained acceptance, which enabled AEG to become a global company.
