Systematic Motor Drive Reliability Improvement Methodology Using Fault-Tolerant Modular Motor Drives

The vision of electrically-propelled aviation presents many technical challenges that must be overcome, including orders of magnitude improvements in machine-drive reliability. Dividing the machine-drive into redundant three-phase modules to form a Modular Motor Drive (MMD) provides a promising approach for introducing fault tolerance (FT) features that can enhance its reliability. However, achieving major reliability improvements using FT-MMDs cannot be achieved by designing reliable drive modules alone. This paper presents a system-level approach to maximizing the reliability potential of MMDs considering all aspects of their design. This includes the development of fully-isolated machine modules using enhanced electromagnetic and thermal isolation features combined with fault-hardened inverter modules and distributed control. Each of these key features of a fault-tolerant MMD system is discussed, coupled with a Markov chain analysis of the reliability implications of this approach. These techniques have been applied to a scaled technology demonstrator that incorporates features developed originally for an aircraft propulsor machine design. This demonstrator unit has been fabricated, and experimental results are provided for serious faults including inter-turn short circuits and rotor position sensor failures. These tests have successfully demonstrated the validity of the MMD concept, building confidence in its promising future potential.