Harry Ward Leonard
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 century. He became known with his invention, the Ward-Leonard converters worldwide. Even today, equipment, based on this invention, can be found in many industrial plants as well as in elevator control systems of the 21st century.
Early life, marriage and education
Harry Ward Leonard was born on February 8, 1861 in Cincinnati as a child of parents Ezra George Leonard and Henrietta Dana Ward. He was the fourth of her six children and one great-great - grandson of Artemas Ward - a general in the American Revolutionary War. Although his family name " Leonard " and not " Ward -Leonard " was apparent he called himself apparently either Harry Ward Leonard or Leonard H. Ward. In 1895 he married Carolyn Good in Geneva. As a student at the Massachusetts Institute of Technology (MIT) Leonard helped the student newspaper to found " The Tech " and was chairman of the editorial staff. In 1883 he graduated from MIT.
Career
After graduating from MIT Harry Ward Leonard was hired by Thomas Edison, with the aim to introduce the electric energy distribution of Edison in the central power plant. Within just four years, he was promoted to the position of Director-General of the Western Electric Light Company of Chicago. The following year he founded Leonard and Izard, a company that electric trains and equipment for power stations produced. 1889 his company was acquired by Edison and Leonard was the General Manager of the Edison companies in the United States and Canada. 1896 Leonard organized in Hoboken Ward Leonard Electric as a subsidiary of Edison and became its president. On February 19, 1898 Harry Ward Leonard left the company Edison to his own trading company - to register in Bronxville in Westchester County - the Ward Leonard Electric Company. While working for Edison, Harry Ward Leonard has patented a number of inventions and throughout his career he continued to develop new ideas. He has been granted for more than 100 inventions of the electric power supply and control systems, in related components patents.
The Ward-Leonard converters
The Ward-Leonard converters - or even short Leonardsatz - was Harry Ward Leonard's best-known and most enduring invention. It was introduced about 1891 and soon became the most widely used type of electric motor speed control. In a Ward-Leonard drive, a primary converter drives a direct current generator at a constant speed. Controlling the speed of a DC motor connected via the change in the exciting current to the generator.
The Leonardsatz shown is used to supply and control a reciprocating engine of a motor test bed and consists of:
Although probably only a technician with Leonards systems are familiar to many millions of people were transported in lifts, which are driven by Leonard phrases. Electric elevators used since the twenties until the 1980s, Leonard sets and many are also at the beginning of the 21st century still in use.
Various modifications of the Leonard - set were introduced, but they reject is generally interested in Harry Ward Leonard system. Leonard himself - and many others after him - have to be additional control systems patented to control the motor speed. This is, for example, required to automatically adjust for the change in the flow at the speed or variable displacement for controlling the speed of elevators sensitive. ( See in this regard the control of the boat lift Niederfinow. )
In parallel, mechanical solutions of the variable drive speed and other electrical control systems used and new systems have been developed after Leonard's sentence was inserted. Controllers for DC motors based on electron tubes have been developed in the twenties. However, such electronic controls could not replace the Leonard set up at the time, were developed at the thyristor drives in the late sixties. Since the mid 1970s, Ward-Leonard drives are technically outdated, but the replacement of the existing Leonard phrases will probably 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 gave lectures. He died suddenly on February 18, 1915 in New York at the annual dinner of the "American Institute of Electrical Engineers ."