Large adjustable-speed wind-tunnel drive

PROPELLER-drive equipment for use in wind-tunnel work, where airplane model testing is involved, presented no unusual problems until the advent of the present national emergency. The emergency stressed the importance of research work in airplane design, necessitating the application of the largest motor drive so far considered where a fixed frequency supply provided the energy source. Tunnels are now in operation or in the process of construction, powered by drives rated up to 40,000 horsepower. The primary condition for all such drives is variable or adjustable speed over at least a 6 to 1 range, with a large number of speed-control points and accurate speed regulation.