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Harry W. Leonard

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Harry Ward Leonard, born on February 8, 1861, is responsible for hundreds of inventions regarding electrical distribution, control systems, and equipment. He is best known for the Ward-Leonard Control System, which utilizes AC-powered motor generator sets to power DC motors with the motion of the machinery. Mining and construction equipment such as stripping shovels have benefited from this invention. It is also used for the operation of many elevators.

Contents

[edit] History

[edit] Birth and Early Life

Leonard was the fourth of six children born to parents Ezra George Leonard and Henriette Dana Ward in 1861 in Cincinnati, Ohio. His great, great-grandfather, General Artemas Ward, fought in the American Revolution.

Leonard had a growing interest in engineering and enrolled in the Massachusetts Institute of Technology (MIT) to study engineering. He graduated in 1883 at the age of 23 and went to work for Thomas Edison to establish a central-station power distribution system. His hard work was well received and he was promoted to general superintendent of the Western Electric Light Co. of Chicago by the time he was 26. A year later, he set up his own company, the Leonard and Izard Firm, but it was soon acquired by Thomas Edison. Though Leonard was appointed general manager, he left the company in 1898 in order to start his own, the Ward Leonard Electric Co.

Leonard married Carolyn Good in 1895. Their wedding ceremony took place in Geneva, Switzerland.[1]

[edit] Invention

Leonard had patents for more than 100 inventions during his lifetime, many of which are still present today. A New York Times article listing his inventions included: “electrically driven reversible rolling mills, electric mine hoists, locomotives, elevators, gasoline electric trucks, transmission gearing for motor cars, rheostats, automatic switches, electric heaters, and automatic electric lighting systems for railway trains and motor cars and electric distributing systems”.[2]

[edit] Ward Leonard Motor Control System

The Ward Leonard motor control system was devised in 1891. It involves a prime mover (usually an AC or alternating current motor) that operates a direct current or DC generator at a consistent speed. The framework of the generator is connected to a direct current or DC motor. The motor, in turn, is responsible for adjusting the speed of the equipment and does so by altering the output voltage of the generator with the help of a rheostat. The flow of the motor field typically stays unaltered and can be reduced at times to increase the speed of the base. Ward Leonard systems typically include an exciter generator that is operated by the prime mover in order to field power supply from the DC exciter.[3]

The Ward Leonard motor control system has been useful for many different concepts and industries. It was particularly useful in the development of steam shovels by manufacturers such as Marion Steam Shovel Co. and Bucyrus Co. Both utilized the Ward Leonard motor control system for their steam powered shovels and excavators because without it, large machines could not get the full power required from electric motors. The Ward Leonard system, using AC powered generator sets to transmit power to DC motors, allows maximum pull for the machine’s motor while preventing it from burning out.

The first shovel to utilize this system was the 225-B, produced by Bucyrus, and the 300-E, manufactured by Marion. Once the system was incorporated into these models, it became the standard configuration for all electric shovels.[4]

[edit] Death

Leonard died on February 18, 1915 while attending a dinner for the American Institute of Electrical Engineers in New York. His death occurred at the Hotel Astor when he proceeded to take off his overcoat. He commented that he had felt a snap in his neck and within 15 minutes, he had died. A doctor was present but was unable to prevent Leonard’s death. Leonard’s wife requested that information of the condition that led to his death be withheld from the public.[5]

[edit] References

  1. Who is Ward Leonard? Ward Leonard, 2008-09-27.
  2. H. Ward Leonard Dies. The New York Times, February, 1915. (accessed: 2008-09-27)
  3. Who is Ward Leonard? Ward Leonard, 2008-09-27.
  4. Haddock, Keith. The Earthmover Encyclopedia. Motorbooks: St. Paul, 2003.
  5. H. Ward Leonard Dies. The New York Times, February, 1915. (accessed: 2008-09-27)