- Harry Ward Leonard
name = Harry Ward Leonard
image_width = 229px
caption = Harry Ward Leonard
February 8, 1861
Cincinnati, Ohio, U.S.A
February 18, 1915
New York, U.S.A
nationality = American
inventor, electrical engineer
Ward Leonard motor control system
Harry Ward Leonard (
February 8, 1861– February 18, 1915) was an electrical engineerand inventorwhose 30-year career spanned the late 19th century and the early 20th century. He is best known for his invention, the Ward Leonard motor control system. Equipment based on this invention remained in service into the 21st century.
Early life and heritage
Harry was born on February 8, 1861 in
Cincinnati, Ohioto Ezra George Leonard and Henrietta Dana Ward. He was the fourth of their six children. He was a great great grandson of American Revolutionary WarGeneral Artemas Ward. Although his surname was evidently “Leonard” and not “Ward-Leonard,” he apparently identified himself as either Harry Ward Leonard or H. Ward Leonard. In 1895, Harry was married to Carolyn Good in Geneva, Switzerland.
As a student at the
Massachusetts Institute of Technology(MIT), Harry was instrumental in founding the student newspaper, The Tech, and served as the president of the paper’s board of directors. He graduated from MIT in 1883. [cite web | last = | first = | title = The Tech | work = Vol. 36. No. 52 | publisher = Massachusetts Institute of Technology | date = 1916-11-22| url = http://www-tech.mit.edu/archives/VOL_036/TECH_V036_S0100_P001.pdf | accessdate = 2006-08-08 ]
After graduating from MIT, Mr. Leonard was employed by
Thomas Edisonto help introduce the Edison central-station electric power distribution system. Within four years, he was promoted to the position of general superintendent of the Western Electric Light Company of Chicago, Illinois. The following year, he established Leonard and Izard, a firm that set up electric railways and generating stations. In 1889, his firm was acquired by Edison and Leonard became the general manager of the Edison operations in the United States and Canada. In 1896, Leonard organized and became president of Ward Leonard Electric as an Edison company in Hoboken, New Jersey. In 1898, Mr. Leonard left the Edison organization and incorporated his own [http://www.wardleonard.com Ward Leonard Electric Company] on February 19, 1898 in the village of Bronxville in Westchester County, New York. [cite web | last = | first = | title = Westchester County Archives | work = Incorporation Records, 1876-1914 -- Personal Name Index -- L-M A-0050 (8), p. 64 | publisher = Westchester County, New York | date = 1898-02-19| url = http://www.westchestergov.com/wcarchives | accessdate = 2006-08-07 ]
While working for Edison, Mr. Leonard patented a number of inventions and he continued developing new ideas throughout his career. He was granted patents for more than 100 inventions of electrical distribution and control systems and related equipment.
The Ward Leonard motor control system
The Ward Leonard motor control system was Mr. Leonard’s best known and most lasting invention. It was introduced in about 1891 and soon became the most widely used type of
electric motorspeed control.
In a Ward Leonard system, a drives a
direct current(DC) generator at a constant speed. The armature of the DC generator is connected directly to the armature of a DC motor. The DC motor drives the load equipment at an adjustable speed. The motor speed is adjusted by adjusting the output voltageof the generator using a rheostat to adjust the excitation current in the field winding. The motor field current is usually not adjusted, but the motor field is sometimes reduced to increase the speed above the base speed. The prime mover is usually an alternating current(AC) motor, but a DC motor or an engine might be used instead. To provide the DC field excitation power supply, Ward Leonard systems usually include an exciter generator that is driven by the prime mover. [cite book | first=Charles S. | last=Siskind | authorlink= | coauthors= | year=1963 | title=Electrical Control Systems in Industry | edition= | publisher=McGraw-Hill, Inc. | location=New York | id= ISBN 0-07-057746-3 ] [cite web | last = Leonard | first = H. Ward | title = Electrical Transmission of Power patent no. 463,802 | work = | publisher = United States Patent Office | date = 1891-11-24| url = http://patimg1.uspto.gov/.piw?Docid=00463802&idkey=NONE | accessdate = 2006-08-10]
Although only technical specialists are likely to be familiar with Ward Leonard systems, many millions of people have ridden in
elevatorspowered by Ward Leonard drives. From the 1920’s through the 1980’s most electrically driven elevators used Ward Leonard control and many systems remained in use at the beginning of the 21st century. [cite conference | first = A.B. | last = Kulkarni | authorlink = | coauthors = | title = Energy consumption analysis for geared elevator modernization: upgrade from DC Ward Leonard system to AC vector controlled drive | booktitle = Conference Record of the 2000 IEEE Industry Applications Conference | pages = vol.4, pp.2066-2070 | publisher = Institute of Electrical and Electronics Engineers | date = Oct 2000 | location = | url = | doi = | id = | accessdate = ]
Many variations of the Ward Leonard system have been implemented, but they have generally continued to be called Ward Leonard systems. H. Ward Leonard and many others have patented auxiliary
control systemsused to regulate the motor speed as required to automatically perform specific tasks such as controlling pumpspeed to regulate flow.
Mechanical types of
adjustable-speed drives and other electrical types continued to be used and new types developed after the Ward Leonard system was introduced. Electron tubetypes of DC motor controls began to be developed in the 1920’s but electronic controls didn’t seriously begin to displace the Ward Leonard system until thyristorcontrolled drives were developed in the late 1960’s. By the mid 1970’s, Ward Leonard drives were rapidly becoming obsolete, but the replacement of existing Ward Leonard drives has continued past the end of the 20th century.
H. Ward Leonard was an active member of the
American Institute of Electrical Engineers, publishing technical papers, attending meetings and making presentations. He died suddenly on February 18, 1915 in New York while attending the annual dinner of the American Institute of Electrical Engineers. [cite web | last = Everett | first = Jasen M.; Ed. | title = “1915.” The People's Chronology | work = | publisher = Thompson Gale; eNotes.com | date = 2006 | url = http://history.enotes.com/peoples-chronology/year-1915/energy | accessdate = 2006-08-07 ]
Booster (electric power)
Ward leonard control
*cite web | last = Leonard | first = H. Ward | title = Descendants Of William Ward of Sudbury Born Abt 1603, and Other Related Families| work = | publisher = rootsweb.com | date = 2006 | url = http://worldconnect.genealogy.rootsweb.com/cgi-bin/igm.cgi?op=GET&db=rckline-wards&id=I14813 | accessdate = 2006-08-08
*cite journal | last = The Editors | first = | authorlink = | coauthors = | title = Technology for Electrical Components | journal = Power Transmission Design | volume = | issue = | pages = 25–27 | publisher = | date = Nov 1989 | url = | doi = | id = | accessdate =
*cite journal | last = Staff | first = | authorlink = | coauthors = | title = Motor Speed Drive Survey | journal = Instruments and Control Systems | volume = | issue = | pages = 69–70 | publisher = | date = Dec 1971 | url = | doi = | id = | accessdate =
*Citation | last = | first = | author-link = | last2 = | first2 = | author2-link = | title = H. Ward Leonard Dies | newspaper = The New York Times | pages = archives | year = 1915 | date = February 19, 1915
url = http://query.nytimes.com/gst/abstract.html?res=950CE6DD1238E633A2575AC1A9649C946496D6CF
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