A linear brushless doubly-fed machine drive for traction applications

This paper proposes a new form of traction drive for rapid transit applications and describes work currently undertaken to investigate its viability. A brief background description of linear induction motor propulsion systems and the problems and limitations experienced in their practical application is given. The principle is introduced of the adjustable-frequency self-cascaded induction machine, or brushless doubly-fed machine and its advantages of synchronous operation and significantly reduced power converter rating are explained. The linear counterpart of the brushless doubly-fed machine is developed and its perceived advantages and disadvantages for traction application are discussed. The design, and testing to confirm design parameters, of a laboratory machine is described and discussed with respect to its intended application. Finally, predictions of the performance of the drive at speeds commensurate with a typical mass transit system are presented