How did magnetic-coupled variable speed drives evolve?
Foot Mounted Style In the 1940’s and 50’s, magnetic coupled devices known as eddy current clutches were effectively used with AC motors and were quickly becoming a popular method of varying the speed of many industrial loads. [Fig 1] Although bulky and inefficient, these workhorses were quite reliable and were used in applications such as punch presses, conveyors, winders, and other machine tool situations. These were oversized foot mounted units that initially were designed as a separately housed clutch assembly with an input shaft and an output shaft to be coupled in line between the motor and the load. Also offered were motor and clutch combination (one piece) packaged units. In those days, the primary focus was in functionality, performance and maintainability, as energy efficiency was not as important a factor as it is today. Shaft-Mounted Styles In the 1960’s some of the first commercially available motor shaft-mounted magnetically coupled drives were offered to the industry. Thi
