Multi-phase permanent magnet motor drives for fault-tolerant applications

The recent markets crisis imposes the adoption of advanced technical solutions to match the requirements of energy efficiency, promoting a gradual transformation in the field of mechanical actuators for hazardous applications and moving the attention to more electric and efficient systems. Nevertheless the adoption of the electromechanical actuators are still limited in those fields that require a high degree of reliability, especially in the cases that involve huge hazard for peoples and environment or failures in systems characterized by heavy out-of-service or restarting costs. Multi-phase motor drives are gaining a growing interest because they permit a boost in torque and power density, allowing the design of very compact high efficiency drives with good improvement by the reliability point of view. The present paper recalls the basic concepts of multi-phase fault-tolerant design and illustrates their adoption in the development of two different systems for aircraft application such as a flap actuator and a cart lift system. Design details will be presented. Reports of analyses and tests carried out on the drives prototypes will be included to confirm the fault-tolerance capabilities with respect to the lack of one or two phases.