The paper describes a variable-voltage induction-motor fan drive, in which the rotor is constructed of hollow unlaminated steel and is cooled using the rotating-heat-pipe principle. A procedure for performance computations is presented, and the special properties of fan drives with unlaminated rotors are demonstrated by both theoretical and tested results for an experimental machine. It is shown that the design successfully overcomes the normal problem of fan-drive cooling in the region of slip equal to ⅓. Difficulties associated with losses at low slip are identified, and ways of relieving this problem are examined.