AC Adjustable-Speed Drives with Electronic Power Converters-the Early Days

Some of the early electronic power converters utilized mercury-arc rectifiers such as thyratrons and ignitrons. Their use in an-ac adjustable-speed drive began about 50 years ago. The first commercial application in the United States was made to an induced draft fan at the Logan station. This drive was in service for about 25 years. The early history of ac adjustable-speed drives which employed electronic power conversion is reviewed.