Linear induction motors

Abstract

The first half of the paper is concerned with the fundamental differences between linear induction motors and their more conventional rotating counterparts. In particular, the effects of the discontinuities which are necessarily introduced either in the stator (‘short stator’ effects) or in the rotor (‘short rotor’ effects) are discussed theoretically. Such discontinuities are shown to involve transient conditions in a linear motor, even when the machine runs at constant speed. The exploitation of double-sided and tubular stators is also discussed.The second part of the paper deals with practical applications of linear induction motors. It includes a brief account of the development of a linear motor which produces a reciprocating motion of stable amplitude without the necessity for any switching device. The possible applications of this type of motor to the textile industry are examined. The use of linear motors as liquid-metal pumps is examined in the light of the earlier theory, and the final section suggests an unusual outlook on induction-motor design which was inspired by the study of linear motors.