Dolivo-Dobrovol’skii, Mikhail Osipovich
Born Dec. 21, 1861 (Jan. 2, 1862), in St. Petersburg; died Nov. 15, 1919, in Heidelberg, Germany. Russian electrical engineer; developer of three-phase current technology.
Dolivo-Dobrovol’skii entered the Riga Poly technical Institute in 1878 but was expelled for involvement in student political activities. In 1884 he graduated from a higher technical school in Darmstadt, Germany, and went to work as a designer for the plants of T. Edison’s electric company (subsequently theAllgemeine Elektrizitats-Gesellschaft, of which he became director in 1909).
Dolivo-Dobrovol’skii improved electromagnetic ammeters and voltmeters for measuring direct and alternating current (1887-88). He successfully applied the principle of the motor with a rotary magnetic field to other kinds of measuring devices (1892). He also developed instruments to eliminate noise in telephones from heavy-current electrical networks (1892) and invented a method for splitting DC voltage based on the use of a fixed induction coil, which he called a voltage divider (1893).
In 1888, Dolivo-Dobrovol’skii built the first three-phase AC generator with a rotary magnetic field (power, 2.2 kilowatts) and proposed an asynchronous three-phase AC motor using a cast-iron rotor with a mounted hollow copper cylinder. Soon thereafter the design of the asynchronous electric motor was improved significantly by using the “squirrel wheel” type rotor (1889). During this period he also developed all the elements for three-phase AC circuits, including three-phase current transformers (1890), starting rheostats, meters (for example, the phase meter, 1894), and star and triangle switching systems for generators and motors. In 1891 at the World Electrical Engineering Exhibition in Frankfurt-am-Main, Dolivo-Dobrovol’skii demonstrated the world’s first three-phase system for transmitting electric power over a distance of 170 km. He was the first to propose the widely used method of damping an electric arc in switches (1910-14). In 1919 he advanced the thesis that the transmission of electric power by alternating current over great distances (hundreds and thousands of km) would be inexpedient because of considerable losses in the lines.