Loren Frank Stringer


Loren Frank Stringer
Associated organizations
Westinghouse Electric Corporation
Fields of study
Power electronics
IEEE Lamme Medal, William E. Newell Award


Loren Frank Stringer was born on September 28 of 1925. He earned a BS in Electrical Engineering from the University of Texas in 1947, and a MSEE from CalTech in 1947 and a PhD from the University of Pittsburgh in 1963. He joined the Westinghouse company in 1947. In 1958, he was appointed Manager, Development Engineering, Systems Control Division and in 1963 he was appointed Director, Thyristor Drive Systems Development Group, with the responsibility for directing and coordinating the Corporate effort involved in the development of high power thyristor drive systems. The immediate result of this effort was a 10,000 HP reversing mill and a 40,000 HP continuous hot strip mill for Alcoa, the world's first thyristor powered continuous mill.

In 1965, Dr. Stringer was appointed Consulting Engineer and Director of Advanced Development, Systems Control Division. In 1972, Dr. Stringer became Division Engineering Manager, Industrial Equipment Division, Buffalo. In this capacity, he was responsible for planning and implementing strategic engineering power electronics programs for both the Industial Equipment and Industry Systems Division. With the formation of the Power Electronics and Drive Systems Division in 1979, Dr. Stringer became the Division Engineeering Manager with responsibility for all design and development engineering for the Division.

"In addition to his contributions in the field of Mill Automation, Dr. Stringer was responsible for the planning, design, and development of many power electronic products such as adjustable frequency, thyristor cycloconverter synchronous motor drive, for the Yankee dryers; 6500 KW wound rotor, thyristor cycloconverter excited, induction generators for load compensation of excavator distribution systems; also pulse width modulated, voltage source, self-commutated, thyristor inverter induction motor drives for machine tools; also a 25 megawatt, 25/60 hertz frequency changer for a steel mill distribution system; also a thyristor converter starting system for a 100 megawatt pumped storage facility; also a 16 megawatt, voltage source, harmonic neutralized, self-commutated thyristor inverter, this perhaps the largest ever built, for a linear induction motor drive; and finally thyristor DC drives for such diverse applications as feed and spindle drives for machine tools, mine hoists, arc furnace electrode hoists, paper machines, rolling mills, uniterruptable power supplies, wire drawing machines, test stands, and many others in the electrochemical and transporation industries.

Dr. Stringer was instrumental in the planning, development, design, and start-up of the adjustable frequency, load commutated, current source, thyristor inverter, 3600 HP synchronous motor drives for induced draft fans that were installed at the Bayshore Station of the Toledo Edison Company in 1979. Although the basic principle of this drive had been implemented in extremely rudimentary forms using thyratrons and Ignitrons some fifty years before, this appears to have been the first large scale commercial application in the U.S. of such technology.

Dr. Stringer planned and directed the development of a fully microprocessor based digital controller for static power converter drive systems that included all sequencing, protective, diagnostic, display, gating, and feedback control functions. This control has been employed in over a hundred drive systems, both AC and DC, in the steel, paper, chemical, and utility industries.

Dr. Stringer was the recipient of a Westinghouse Special Patent Award, the B.G. Lamme Scholarship, and the Westinghouse Order of Merit. He was also awarded the IEEE's Lamme Medal and William E. Newell Award in 1984. Dr. Stringer held 24 United States Patents. He was past Chairman of the IEEE Static Power Converter Committee, past Chairman of the N.E.M.A. Static Power Converter Section, Chairman of the Technical Support Subcommittee of the American National Standards Institute, Comittee C34, and was Technical Advisor to the U.S. National Committee of the International Electrotechnical Commission. He was also the Chairman of the Industrial Power Converter Systems Department of the Industry Application Society of the IEEE. Dr. Stringer was elected a Fellow of the IEEE in 1979 for contributions to the development and application of solid state power electronic systems.

Dr. Stringer served in the Naval Reserve during World War II. He was a member of Tau Beta Pi, the Caltech Varsity T Association, and the New York Academy of Sciences. He was a life member of the Association of Iron and Steel Engineers.