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Modular Fault-Tolerant Machine Design with Improved Electromagnetic Isolation for Urban Air Mobility (UAM) Aircraft

The electric propulsion machines used in Urban Air Mobility (UAM) aircraft must achieve high power density, efficiency, and reliability. A modular stator configuration (i.e., breaking the machine into multiple three-phase groups) is a promising approach for achieving high levels of stator and power electronics fault tolerance. This paper proposes a stator configuration using double-layer concentrated windings that offers an improved tradeoff between the electromagnetic isolation characteristics of individual modules and their power density metrics compared to previously reported modular stator configurations. The proposed stator structure utilizes a unique stator tooth tip structure that increases the leakage inductance. The post-fault performance characteristics of the new configuration have been investigated via simulation for both open-circuit and short-circuit faults. These results demonstrate that the healthy module exhibits very little impact when either fault type is applied to an adjacent module, even during the initial transient period following the fault application. The modular motor approach is applied to a quadrotor aircraft application and analyzed for both healthy and faulted operation. The machine is estimated to achieve 14.1 kW/kg active power density and 96.0% efficiency during rated operation at 70 kW, 8000 rpm.