Harry Ward Leonard

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Harry Ward Leonard (born February 8, 1861 in Cincinnati , Ohio , † February 18, 1915 in New York ) was an American electrical engineer and inventor . His 30-year career spanned from the late 19th to the early 20th centuries. He became known worldwide with his invention, the Ward-Leonard converter . Equipment based on this invention can still be found in many industrial plants and elevator controls of the 21st century.

Early life, marriage and education

Harry Ward Leonard was born on February 8, 1861 in Cincinnati to parents Ezra George Leonard and Henrietta Dana Ward. He was the fourth of their six children and a great-great grandson of Artemas Ward - a general in the American War of Independence . Although his family name appeared to be "Leonard" rather than "Ward-Leonard", he apparently called himself either Harry Ward Leonard or H. Ward Leonard . In 1895 he married Carolyn Good in Geneva . As a student at the Massachusetts Institute of Technology (MIT), Leonard helped found the student newspaper "The Tech" and became editor-in-chief. In 1883 he graduated from MIT.

Career

After graduating from MIT, Harry Ward Leonard was employed by Thomas Edison with the aim of introducing Edison's electrical power distribution to the central power station . Within just four years, he was promoted to the position of general manager of the Western Electric Light Company of Chicago . The following year he founded Leonard and Izard , a company that manufactured electric trains and equipment for power plants. In 1889 his company was acquired by Edison and Leonard became the general manager of Edison operations in the United States and Canada . 1896 organized Leonard in Hoboken the Ward Leonard Electric as a subsidiary of Edison and became its president . On February 19, 1898, Harry Ward Leonard left Edison to register his own trading company - the Ward Leonard Electric Company - in Bronxville, Westchester County . While working for Edison, Harry Ward Leonard patented a number of inventions and throughout his career he continued to come up with new ideas. He has been granted patents for more than 100 inventions of electrical power supply and control systems for related components.

The Ward-Leonard converter

The Ward-Leonard- converters - or short Leonardsatz - was Harry Ward Leonard's best-known and most enduring invention. It was introduced around 1891 and soon became the most widely used type of electric motor speed control. In a Ward-Leonard converters a prime mover drives a DC - generator at a constant speed. The speed of a connected DC motor is regulated by changing the excitation current on the generator.

Leonard converter

The Leonard set shown serves to supply and control a pendulum machine of an engine test bench and consists of:

  1. Asynchronous motor as drive machine
  2. Main generator (separately excited DC machine )
  3. Exciter generator ( shunt machine )

While probably only technicians are familiar with Leonard's systems, many millions of people have been transported in elevators powered by Leonard sets . Electric elevators have been using Leonard sets from the 1920s through the 1980s, and many are still in use as the 21st century began.

Various modifications of the Leonard Theorem have been introduced, but they are generally based on Harry Ward Leonard's system. Leonard himself - and many others after him - have patented additional control systems to regulate the engine speed. This is necessary, for example, in order to automatically adjust the speed to change the flow rate on variable displacement pumps or to precisely control the speed of elevators. (See the control of the Niederfinow ship lift .)

In parallel, mechanical variable speed drive solutions and other electrical controls were used and new systems developed after the Leonard theorem was introduced. Controls for direct current motors based on electron tubes were developed in the twenties. Such electronic controls could not replace the Leonard set until the point in time when thyristor-controlled drives were developed at the end of the sixties. Ward-Leonard drives have been technically obsolete since the mid-1970s , but the replacement of the existing Leonard sets is likely to last until the end of the 21st century.

Sudden death

Harry Ward Leonard was an active member of the American Institute of Electrical Engineers , published technical papers, organized various meetings and lectured. He died suddenly on February 18, 1915 in New York at the annual dinner of the American Institute of Electrical Engineers.

swell

  1. ^ The Tech. (PDF; 291 kB) In: Vol. 36. No. 52nd Massachusetts Institute of Technology, November 22, 1916, accessed August 8, 2006 .
  2. ^ Westchester County Archives. In: Incorporation Records, 1876-1914 - Personal Name Index - LM A-0050 (8), p. 64. Westchester County, New York, February 19, 1898, accessed August 7, 2006 .
  3. ^ Alfred Böge: The technician manual . Vieweg-Verlag, Braunschweig / Wiesbaden 1999, ISBN 3-528-34053-3 .
  4. ↑ H. Ward Leonard: Electrical Transmission of Power patent no. 463,802. United States Patent Office, November 24, 1891, accessed August 10, 2006 .
  5. ↑ Jasen M .; Ed. Everett: "1915." The People's Chronology. (No longer available online.) Thompson Gale; eNotes.com, 2006, formerly in the original ; Retrieved August 7, 2006 .  ( Page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2Template: Dead Link / history.enotes.com  

literature

personal data
SURNAME Ward Leonard, Harry
ALTERNATIVE NAMES Leonard, H. Ward
BRIEF DESCRIPTION American electrical engineer
DATE OF BIRTH February 8, 1861
PLACE OF BIRTH Cincinnati
DATE OF DEATH February 18, 1915
Place of death new York