Alternating Current Wiring and Distribution (Classic Reprint)
(Excerpt from Alternating Current Wiring and Distribution
...)
Excerpt from Alternating Current Wiring and Distribution
When a current is started ifl a wire each line or element of increasing current tends to induce counter E. M. R.'s or reverse currents in the metal in its neighborhood; thus all the metal in the Wire is subjected to two opposing forces, one to create current flow and the other to retard it. The cen tral portions Of the wire are surrounded by these retarding influences while the outer surface Of the wire can receive them from one side only. The result Of this is that when a wire is suddenly sub jected to an E. M. F. The current begins first to flow on its surface, and an appreciable time elapses be fore the full current density reaches the centre Of the wire. Thus the current may be said to begin on the outside and soak into the wire. If the al ternations are sufficiently frequent the central por tions of the wire are practically never reached by the current, and the copper available for conduct tivity is little greater than what it would be if the conductor were a tube of similar outside diameter. The thickness of the walls of the equivalent tube will be less as the frequency increases. It is easy to understand that this effect is relatively greater with large wires than with small also, that it will be much greater with iron than with copper wires.
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(Mr. Emmet is well known to the engineering profession as ...)
Mr. Emmet is well known to the engineering profession as an engineer who for many years has carried heavy responsibilities in the electrical and mechanical industries. His book will delight his many friends and admirers and will inspire and interest the young engineer. - from the foreword
William Le Roy Emmet was an electrical engineer who made major contributions to alternating current power systems including the design of large rotary converters.
Background
He was born on Travers Island near what is now New Rochelle, New York, the second of six sons and fourth of ten children of William Jenkins Emmet and Julia Colt (Pierson) Emmet. His great-grandfather was Thomas Addis Emmet (1764 - 1827), noted Irish patriot, whose brother Robert was the tragic hero of an ill-fated Irish uprising.
His father operated a sugar business successfully during the Civil War, but its failure shortly after left the family in chronically straitened financial circumstances.
His great-grandfather was Thomas Addis Emmet (1764 - 1827) [q. v. ], noted Irish patriot, whose brother Robert was the tragic hero of an ill-fated Irish uprising.
His grandfather, also named Robert, was a noted lawyer and judge.
Emmet later characterized his mother, the granddaughter of Jeremiah H. Pierson, Congressman from New Jersey and prominent Ramapo Valley mill operator, as a "beautiful" woman of "extraordinary intelligence and exalted ideals. "
The playwright Robert E. Sherwood was one of his nephews. During a happy childhood in rural Westchester County, Emmet developed a lifelong fondness for nature, fishing, sports, and music.
Education
He was an indifferent student in three elementary schools.
Financial stringency led him to apply to the United States Naval Academy, where, after first failing the admissions examination and taking work at the Maryland Agricultural College, he was admitted in 1876.
He graduated fifty-fourth in a class of seventy-six in 1881.
Career
Naval retrenchment brought about his discharge in 1883, although he served during the Spanish-American War as navigator on a collier and during World War I as a member of the Naval Consulting Board.
Between 1883 and 1891 Emmet held various posts, the most important being with Frank J. Sprague [Supp. 1], pioneer in electric traction, for whom he did installing and troubleshooting on electric street railways in various cities.
The job confirmed Emmet's interest in electrical engineering. In 1891 he joined Samuel Insull [Supp. 2] and the Edison General Electric Company in Chicago. He moved the following year to the New York offices of the newly organized General Electric Company and in 1894 to its Schenectady plant, where he remained until retirement.
During his early years, Emmet was responsible for a variety of technical improvements in electrical apparatus. While working for Sprague he improved motors, patented a new trolley device, and contrived a superior insulating material of varnished cambric, a material he developed further in his years with General Electric.
His interest in electric distribution problems led to a pioneering text, Alternating Current Wiring and Distribution (1894). With E. M. Hewlett he developed oil switches, essential for high-voltage work. For about a decade Emmet was responsible for G. E. 's participation in the epochal Niagara Falls power project; his converters, transmission lines, and generators contributed significantly to its success.
About 1899 Emmet turned his attention to steam turbines, particularly as a source of power for electric generators. Working with Charles G. Curtis, he was chiefly responsible for developing the first two generations of successful steam turbines which, in less than a decade, effectively eliminated reciprocating engines as prime movers in steam generating plants.
Emmet also helped introduce mica tape insulation and improved cooling systems in generators which developed insulation breakdowns from high-speed high-temperature operation. By 1909 the steam turbine had achieved such economies that Emmet began to campaign for turbine-generated electrical propulsion on ships.
His initial installation on the 20, 000-ton naval collier Jupiter proved more efficient than reciprocating engines and both more efficient and more reliable than geared turbine engines. During World War I, General Electric provided Emmet-designed geared turbines for some three hundred merchant ships and fifty destroyers and subsequently produced turbo-electric drives for the new battleship New Mexico and for the two battle cruisers that were ultimately converted into the aircraft carriers Lexington and Saratoga.
Emmet's later years were devoted to the mercury vapor turbine. Mercury with its high boiling point and other physical properties offered substantial theoretical promise as a thermodynamic fluid in very high temperature ranges, but the long and costly development of a practical device extended beyond Emmet's lifetime.
Between 1928 and 1949 General Electric built eight mercury-steam generating plants, including developmental models.
The designs were technically sound and economically efficient, but the development of very-high-pressure high-temperature steam turbines doomed the mercury-vapor engines to economic extinction. In large degree self-taught, Emmet had a profound faith in experimentation.
But he also respected and made good use of both theory and mathematics. Persistent and determined, he deeply believed the secret of engineering success to be close attention to detail.
He died at the age of eighty-two at his nephew's home in Erie, Pennsylvania. He was buried in Arlington National Cemetery.
During his youth he was, he reports, a deeply religious Anglican, but in later years religion played little part in his life.
Views
A thoroughgoing individualist who argued that creative ideas came from individuals, not committees, he nevertheless recognized the necessity for large organizations and won the confidence and support of his superiors in General Electric, who gave him substantial independence in his work.
Membership
He was a member of the American Philosophical Society (1898) and the National Academy of Sciences (1921)
Connections
Emmet never married; he lived successively with two of his brothers and a nephew.