Fault-Tolerant Topologies with Halbach Array and PM-Free Multi-Stage Multi-Module Electric Machines for Electric Aircraft Propulsion

Electrically propelled aircraft require electric machines which are compact and efficient at largely different operating conditions and with maximal fault tolerance. This paper studies the fault tolerance of machine topologies with two electromagnetic stages mechanically coupled on the same shaft. A coreless axial flux PM (CAFPM) motor stage consists of two Halbach array PM rotors and two stators with integrated cooling to enable high efficiency at high current density. A second stator DC-excited synchronous (SDCES) motor stage operates using AC 3-phase and DC stator windings employing concentrated non-overlapping toroidal coils with a reluctance consequent-pole rotor. The combination of two stages can take advantage of the ultra-efficient, lightweight, and fault-tolerant aspects for one electric machine with multiple independent sections or modules per stage. Systematic analysis is performed assuming modular construction and derated operation is simulated for both stages with finite element analysis (FEA). Markov chain reliability analysis is employed to illustrate system survivability, considering multiple combinations of single-point faults that enable cruising power operation for a large hydrogen-fueled blended wing aircraft with distributed electric propulsion.