Evaluation of motor-drive segmentation strategies for fault-tolerance

High availability and safety is a major concern for many actuation applications. Fault-tolerant electrical machines and power converters help achieving this goal but component overrating and system complexity have to be minimised for favourable system designs. This paper will assess several segmentation strategies of fault-tolerant permanent magnet machines on the example of an aerospace actuation system and examine the impacts on system weight and complexity. Considerable detail will be presented on the integration of multi 3-phase machine units in a common motor housing alongside with a detailed comparison between axial and circumferential segmentation, which to the knowledge of the authors has not been published before. A helicopter primary flight control actuation application is used to compare segmentation strategies. Initial results suggest that circumferential machine segmentation and a single layer concentrated winding arrangement are most suitable for applications with a high level of required fault tolerance and high peak to rated torque and speed ratio.