The Woman Behind the Clarke Calculator

Edith Clarke was an American electrical engineer and mathematician whose noteworthy contributions include two patents related to electrical power transmission, various papers on power distribution and synchronous machines, and an extensive electrical engineering textbook for higher education.

 

Edith Clarke. Image used courtesy of Edison Tech Center

 

Clarke was the first female to receive a degree in electrical engineering from the Massachusetts Institute of Technology (MIT), the first female EE professor in the U.S., and the first female elected fellow of the American Institute of Electrical Engineers (now IEEE).

 

Early Life and Education

Born in Maryland in 1883, Edith Clarke was orphaned at a young age. Her early life was marked by a passion for math and science. At 18, she used her inheritance to fund her college education. 

Clarke studied math and astronomy at Vassar College in New York. After graduating in 1908, she taught math in San Francisco at a private girls’ school, then later at Marshall College in West Virginia. 

Her time as an engineer started at the University of Wisconsin, where she enrolled in civil engineering courses in 1911. The summer after her first year, she accepted a job at AT&T as a human “computer,” working for George Campbell and helping him address problems of long-distance electrical transmissions using mathematical applications. During World War I, Clarke worked for the Transmission and Protection Engineering Department, leading a group of female “computers.”

In 1918, she started classes in electrical engineering at MIT, receiving her master’s degree in 1919. Clarke’s master’s thesis was titled “Behavior of a lump artificial transmission line as the frequency is indefinitely increased.”

 

Clarke had a passion for math and science. Image used courtesy of Pixabay

 

The Clarke Calculator

Early in her career, Clarke started developing mathematical methods that dramatically simplified and improved the calculation efforts of electrical engineers, despite having trouble finding work herself as an engineer.

After completing her studies at MIT, Clarke was hired by General Electric (GE), continuing her work as a “computer.”

The occupation of “computer” was first described in the early 17th Century, referring to one or more researchers who perform large-scale computations without electronic assistance.

In 1921, she filed her first patent. She invented a “graphing calculator,” the Clarke calculator, a device that could perform complex calculations related to power systems. The calculator was the first electronic calculator designed specifically for use in the power industry. It significantly impacted how engineers approached complex calculations; it could solve equations involving voltage, electric current, and impedance. 

The device was small and portable, allowing engineers to take it to job sites, where they could make calculations on the spot. The Clarke calculator was a forerunner of the electronic calculators now widely used in engineering and other fields. 

 

Engineering Work

After filing her patent, Clarke took a leave of absence from GE to teach physics at the Constantinople Women’s College in Turkey. She returned to GE in 1922 when she was offered a salaried position as an electrical engineer, the first woman to work as a professional electrical engineer in the U.S. 

In 1926, Clarke was the first woman to deliver a paper to the American Institute of Electrical Engineers, again using mathematical applications to improve the work of engineers. She developed a method for calculating the stability of power systems, which allowed engineers to design power systems that were more reliable and less prone to failure. This method became widely used in the power industry and helped make high-voltage transmission systems more efficient and safe. 

This paper proved to have a great national impact, as transmission lines were becoming longer at the time, leading to heavier loads and an increased risk of system instability. The existing mathematical models at the time were only suitable for smaller systems. Clarke utilized a mathematical method known as the method of symmetrical components to model a power system and its behavior, allowing her and other engineers to identify key characteristics for analyzing larger systems.

 

Transmission lines. Image used courtesy of Pixabay

 

Clarke left GE in 1947 and went to the University of Texas, Austin, where she worked as a professor of electrical engineering until her retirement in 1956.

Today, Edith Clarke remains an inspiration to women in STEM. Her contributions to math and engineering have helped shape the industry. Her pioneering work in developing electronic calculators and graphical methods for solving differential equations continues to be studied and used by engineers worldwide. 

In 1954, Clarke was recognized by the Society of Women Engineers Achievements Award for her many unique contributions to power systems.