A project has been announced in the US to develop lightweight and ultra-efficient electric motors, drives and associated thermal management system for large commercial electric aircraft (writes Nick Flaherty).

The Aviation-class Synergistically Cooled Electric motors with iNtegrated Drives (ASCEND) project brings together an engineering team at Texas A&M University to develop a new axial motor system, with Hyper Tech Research in Ohio working on the cooling.

The teams will develop electric powertrain systems suitable for narrowbody passenger aircraft the size of the current Boeing 737, which can carry 150 to 200 people over a range of more than 2800 nautical miles. They are likely to be paired with a hydrogen fuel cell.

The project aims to deliver power densities of more than 12 kW/kg, with conversion efficiencies of more than 93%. This compares to 6-9 kW/kg for current gasoline-based systems.

The Texas A&M team will focus on powertrain design, fabrication and testing. The axial flux motor’s supply will come from a multi-level inverter using GaN high frequency wideband semiconductors with a thermally conductive nanocomposite electrical insulation.

A two-phase thermal management system with zeolite thermal energy storage will absorb the excess heat generated during take-off. Each subsystem is designed for tight integration with the other subsystems to minimise weight.

Hyper Tech Research is also developing a high efficiency, high power density integrated electric propulsion motor, drive and thermal management system with power levels above 3 MW.

It will use an induction electric machine with a novel thermal management technique for synergistic cooling that safely uses cryogenic bioLNG as the energy source for power generation and a large thermal battery cooling system.

This will allow for a cost-effective motor capable of operating at a higher current density compared with existing conventional non-cryogenic motors without using superconductors.

Also as part of the project, General Electric Global Research is developing a 2 MW fully integrated all-electric aircraft powertrain using a high-voltage, direct drive, synchronous permanent magnet motor with embedded cooling of the windings using supercritical carbon dioxide and high-temperature, high voltage electrical insulation.

The powertrain will feature a modular inverter using SIC transistors. The first step is to demonstrate a 350 kW labscale prototype of the system.