Ferraris, Galileo

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Ferraris, Galileo

(b. Livorno Vercellese, Italy, 31 October 1847; d. Turin, Italy, 7 February 1897)

electrical engineering, physics.

One of four children of a pharmacist, Ferraris became one of the prime electrical innovators of the 1880’s. At age ten he went to live in Turin with a physician uncle, who guided the boy’s education in the sciences and classics. He subsequently spent three years at the University of Turin and two years at the Scuola d’Applicazione di Torino, graduating in 1869 with the title engineer. His doctoral thesis at the university in 1872 was Teoria matematica della propagazione dell’elettricità nei solidi omogenei.

Ferraris then taught technical physics at the Regio Museo Industriale in Turin and also investigated light waves and the optical characteristics of telescopes, especially the phase difference of two waves in sinusoidal motion. This led to the concept of phasedisplaced electrical waves and a rotating electromagnetic field. Further studies in polyphonic acoustics and interference in telephone circuits sharpened Ferraris’ grasp of coacting forces in and out of phase. His continued interest in optics resulted in the publication, in 1876, of the Proprietà degli strumenti diottrici....

Ferraris represented the Italian government on the awards jury at the 1881 International Electricity Exposition at Paris, where he learned of the Deprez system of high-voltage alternating current transmission and low-voltage distribution. He was also a delegate to the Paris conference of 1882 to determine standard electrical units, and in 1883 he was his country’s delegate to the electrical exposition in Vienna. These duties prepared Ferraris for his service in 1883 as president of the international section of the Electricity Exposition at Turin, where he saw the Gaulard-Gibbs transformer. A paper on the transformer, presented before the Academy of Science at Turin in 1885, led to an intensive study of the interlocking relationships of electrical and magnetic forces in the primary and secondary circuits of the transformer system, and he drew heavily on the optical analogy of light polarized elliptically and circularly.

Carrying the notion further, Ferraris visualized the placing of two electromagnets, each fed by a current displaced 90° out of phase, at right angles to each other, thereby producing the equivalent of a revolving magnetic field. This could induce currents in an included copper drum (or rotor), and the resulting torque would be equivalent to the power of an alternating current electric motor—then still the missing unit in the production of an alternating current system. Ferraris constructed such a device and tested it in August-September 1885 by feeding one coil with current from a small Siemens alternator and the second coil with current from a Gaulard transformer. Switching the currents reversed the direction of rotation. Ferraris freely discussed his principle and openly showed his models in classroom and laboratory. He did not apply for patents because he felt a professional pride in discovery and the extension of all knowledge. This was indicated when he wrote; “Above industrial importance I perceive scientific importance, above material use, intellectual use.”

The Ferraris principle led to the design and construction of an alternating-current motor without commutator or brushes, which had a squirrel-cage copper rotor revolving by induction from its surrounding “rotating” stator field; it was asynchronous and self-starting. This type of motor today is responsible for the bulk of conversion of electrical power to mechanical power. Ferraris announced his discovery before the Royal Academy of Sciences at Turin on 18 March 1888. Others later claimed priority for the concept of the rotating field—especially Deprez, Walter Baily, and Nikola Tesla. In litigation in German and U.S. courts between 1895 and 1900, it was established that Ferraris had anticipated the principle but that Tesla had applied it, independently, to motor design. The original Ferraris devices are still preserved at the Istituto Elettrotecnico Nazionale Galileo Ferraris in Turin, an institute inaugurated in 1935 as a center for all forms of electrical research and study.

Ferraris participated in the AEG-Oerlikon effort to extend alternating current systems, as demonstrated in the 175-kilometer Lauffen-Frankfurt transmission line that inaugurated the Frankfurt Electrical Exposition of 1891 (at which he was awarded highest honors). He represented his government and was elected vice-president of the electrical exposition in Chicago in 1893, where the standards for the henry, the joule, and the watt were adopted.


Ferraris’ Opere were published in 3 vols. by the Associazione Elettrotecnica Italiana (Milan, 1902–1904); see also Sulla illuminazione elettrica (Turin, 1879); “Rotazioni elettrodinamiche prodotte per mezzo di correnti alternate,” in Atti dell’Accademia della scienze, 23 (1888), 360–363; and Lezioni di elettrotecnica dettate nel R. Museo industriale italiano in Torino (Turin-Rome, 1897; 2nd ed., 1904).

Bern Dibner

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Galileo Ferraris

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