Electrical Drives for Wide Speed Ranges
G. A. Caldwell, W. H. Formhals · Transactions of the American Institute of Electrical Engineers · 1942
THE electrical drive for a wide speed range is obtained by the addition of a rotating regulator called a Rototrol to a conventional variable voltage system. This combination will give a speed range of 120 to 1 or more, and can be used effectively in many industries to simplify the mechanical design of the machine which it drives. Its use eliminates elaborate gear-change mechanism, clutches, and so forth, and at the same time gives a more flexible control scheme with the complete speed range under the control of the operator without leaving the work or stopping the machine.