A control algorithm of AC-brushless drives for railways traction application

The paper deals with anisotropic PM brushless motors used in railways traction drives. A control algorithm is presented for optimizing performances in a wide speed range. Starting from the assigned torque-speed traction characteristic and taking into account the limit values of armature current and voltage and of air-gap flux magnitude, the expressions of reference values for the current control are found in the different operating regions. Particular attention is devoted to the flux weakening region and to conditions to avoid saturated operations. In order to show the validity of the proposed control algorithm numerical investigation are carried out with reference to some significant operations of a real light-rail traction drive.