Sensorless operation of a fault tolerant PM drive

There is much interest in the use of electric drives for aeroengine fuel pumps on the more electric aircraft. As a safety critical system the drive must possess fault tolerant properties in order to meet the reliability requirements. Previous work has resulted in the development of a six-phase fault tolerant permanent magnet drive for this application. This drive exhibits fault tolerance in both the motor and power electronics but has the weakness of dependence on a single shaft position sensor. This is addressed through the use of a position estimation scheme. The sensorless scheme makes use of a flux linkage-current-angle model to estimate the rotor position. The fault tolerant drive has six independent phases and the voltage and current measurements from each of these phases are used by the estimation scheme. Two different position estimation algorithms are examined based on 'per-phase' and 'all-phase' approaches.