Single Fluid Tuned Winding Induction Motors

This proposal focusses in the development of two high power density and high reliability asynchronous lift motors for Electric Vertical Takeoff and Landing (eVTOL) while being relevant to the NASA Revolutionary Vertical Lift Technology (RVLT) Project. This motors are proposed in response to NASAs A1.06 Vertical Lift Technology for Urban Air Mobility -Electric Motor Fault Mitigation Technology request of advanced technologies supporting electric/hybrid-electric propulsion for the advance air mobility, specifically, to the area of Single Fluid Motor with High Power Density and High Reliability. The key issues in the Phase II program are the redesigning - scale down of the present highly successful Ohio State University megawatt class induction motor to, (1) optimize overall design (poles, topology, size, etc.) from 1 MW class to a 200 kW class UAM eVTOL motor as well as, (2) to operate with single fluid bearings and (3) synergistically integrate the lubrication with cooling in order to operate a single fluid and to achieve maximum power density and reliability. During this program, two full-size motors (with shaft equivalent performances) based on different electromagnetic solutions will be fabricated in order to allow a complete shaft-to-shaft testing program and an apple-to-apple comparative analyze. Both motors will develop 500 kW continuously at 5000 rpm using a proprietary single fluid semi-evaporative cooling and lubrication method. At the end of Phase 2, both motors will be thoroughly tested on a custom built bench test. The aero-propulsion reliability is obviously extremely important, while the UAMs propulsion is the less forgiving of all flying machines. In the case of a total power loss, planes can glide, and helicopters can auto-rotate, but UAMs cannot control a reasonable descent. As such, the UAMs safe flying especially near buildings depends drastically on the motors’ reliability. IEEE found that over 50% of the electric motors' failures are generated by the bearings. Even more, the hunt for high-density motors is mostly rival to the bearing ‘s life. We demonstrated prior the semi-evaporative cooling with a claimed WR of 7.25 kW/kg continuous (still standing). Simulations show that using a single fluid solution and the semi-evaporative cooling, we can overpass the 10 kW/kg psychological barrier with a bearing's life of tens of years. Simulations also show that our motors will generate the rated power even with a phase out or an internal short-circuit. Basically, we are developing the most power-dense motors having also the most reliable configuration based on the single fluid implementation. The overall objectives have been positively enhanced after Phase 1. The original objective to develop two new high-performance induction motors designed with single fluid cooling/lubrication now is increased to three motors and a portable test bench. This positive revision was possible due to the novel solutions developed in Phase 1 related to the rotor and stator constructions, fabrication and assembly technologies. Collaterally, the usage of the semi-evaporative coolant also for lubrication was found less challenging as originally thought. Overall, the cost of prototyping is lower vs. the original estimation and hence more hardware can be build.  The Phase 2 would continue the design, but also includes the building and full testing of at least two prototypes. All the concept motors are asynchronous (induction) type with 18 poles, 9 phase, 750 Hz at 5000 rpm incorporating two-phase semi-evaporative cooling and lubrication.  The minimum targeted power density is 10 kW/kg CONTINOUSLY in a direct drive configuration.     Phase 2 Objectives: Finish the electromagnetic optimization for Evo3 “Largely distorted pole ratio” motor conceived at the end of Phase 2 Prototype design of Evo2 (two layers winding) and EVo3 (single layer distorted aspect ratio) motor. Fabrication of the portable test bench rig. Fabrication of the motors Testing of the motors and refinements

The innovations (related to cooling and lubrications) may be directly and immediately applied to the other area (the first area) of the A1.06 solicitations: Electric Machine/Motor Fault Detection and Fault Mitigation and Megawatt electric propulsion systems in the A1.04 Electrified Aircraft Propulsion subtopic. In addition to eVTOL, UAMs and electric passenger aircraft, NASA can benefit for many applications where lightweight power components are required such as smaller land-based motors and generators. The results of this work can lead to various applications related to high power density rotating machines in a plethora of fields which are not traditionally electrically driven. Transportation and energy are two major relevant application areas with immediate applications for aircraft turbogenerators, aero-propulsion motors, marine propulsion and portable emergency power systems.

This is early/mid-stage (TRL 4) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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