MIT aeroengineers are creating a one-megawatt electrical motor that is a stepping stone toward electrifying commercial airliners. Pictured are some industrial concepts for hybrid-electric aircraft. (Image: Airbus SAS 2023)

A team of MIT engineers is creating a one-megawatt motor that could be a key stepping-stone toward electrifying larger aircraft. The team has designed and tested the major components of the motor and has shown through detailed computations that the coupled components can work as a whole to generate one megawatt of power — at a weight and size competitive with current small aero-engines.

For all-electric applications, the team envisions the motor could be paired with a source of electricity such as a battery or a fuel cell. The motor could then turn the electrical energy into mechanical work to power a plane’s propellers. The electrical machine could also be paired with a traditional turbofan jet engine to run as a hybrid propulsion system, providing electric propulsion during certain phases of a flight.

“No matter what we use as an energy carrier — batteries, hydrogen, ammonia, or sustainable aviation fuel — independent of all that, megawatt-class motors will be a key enabler for greening aviation,” said project lead Zoltan Spakovszky.

The MIT electric motor and power electronics are each about the size of a checked suitcase and weigh less than an adult passenger. The motor’s main components are: a high-speed rotor, lined with an array of magnets with varying orientation of polarity; a compact, low-loss stator that fits inside the rotor and contains an intricate array of copper windings; an advanced heat exchanger that keeps the components cool while transmitting the torque of the machine; and a distributed power electronics system, made from 30 custom-built circuit boards, that precisely change the currents running through each of the stator’s copper windings, at high frequency.

“I believe this is the first truly co-optimized integrated design,” Spakovszky said. “Which means we did a very extensive design space exploration where all considerations from thermal management to rotor dynamics, to power electronics and electrical machine architecture were assessed in an integrated way to find out what is the best possible combination to get the required specific power at one megawatt.”

As a whole system, the motor is designed such that the distributed circuit boards are close coupled with the electrical machine to minimize transmission loss and to allow effective air cooling through the integrated heat exchanger.

“This is a high-speed machine, and to keep it rotating while creating torque, the magnetic fields have to be traveling very quickly, which we can do through our circuit boards switching at high frequency,” Spakovszky said.

To mitigate risk, the team has built and tested each of the major components individually and shown that it can operate as designed and at conditions exceeding normal operational demands. The researchers plan to assemble the first fully working electric motor and start testing it in the fall.

Once the MIT team can demonstrate the electric motor as a whole, the design could power regional aircraft and could also be a companion to conventional jet engines, to enable hybrid-electric propulsion systems. The team also envisions that multiple one-megawatt motors could power multiple fans distributed along the wing on future aircraft configurations. Looking ahead, the foundations of the one-megawatt electrical machine design could potentially be scaled up to multi-megawatt motors, to power larger passenger planes.

“I think we’re on a good trajectory,” Spakovszky said. “We are not electrical engineers by training but addressing the 2050 climate grand challenge is of utmost importance; working with electrical engineering faculty, staff, and students for this goal can draw on MIT’s breadth of technologies so the whole is greater than the sum of the parts. So, we are reinventing ourselves in new areas. And MIT gives you the opportunity to do that.”

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