Mixed-loop control of an asynchronous traction drive based on electromagnetic state stimulator concept

The paper presents a new concept for the traction drive with squirrel-cage induction motor supplied from inverter sourced by high voltage overhead line and working with a reduced switching frequency. A new current - voltage control scheme was proposed for such a drive. This method provides the smooth control variables and combines in one algorithm both a stator current vector oriented control scheme for the exact supervising of the motor torque at the low rotor speed and a scalar control scheme for the appropriate setting of the stator voltage amplitude and its frequency at the high speed. Improved current controller and a new algorithm of reconstruction of the desired stator voltage vector produced by the inverter enabled a significant reduction of the switching frequency.