Sensorless start-up of soft starter driven IE4 motors

This paper presents a sensorless starting procedure for a soft starter driven IE4 direct on line permanent magnet synchronous motor (PMSM). First, the initial position of the rotor is determined using a pulsating current space vector. Subsequently, the motor is started from standstill by the soft starter from a known position. The following firing sequences are calculated on the basis of the flux angle and speed estimated by a reduced Luenberger observer, which needs no additional sensors besides those provided in a standard industrial soft starter. Measurements clearly indicate the potential performance of this starting procedure.