MIT team developing 1MW motor for electric aviation

A team of MIT engineers is developing a 1MW 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 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.

The motor under design is a 1-MW, air-cooled, outer-rotor, Halbach-array PMSM. Component level risk mitigation experiments indicate that the performance of the prototype machine will match the design specifications.

(A Halbach array rotor uses a specific arrangement of magnets to enhance magnetic field strength on one side while significantly reducing the magnetic field on the other side. The most common arrangement is a series of magnets where each magnet is rotated by a certain angle relative to its neighboring magnets. This rotation of magnets creates a non-uniform magnetic field distribution. The concentrated magnetic field on one side provides a stronger and more efficient magnetic interaction with the stator, which can lead to improved torque or power output. The reduced magnetic field on the opposite side can minimize unwanted interactions with other components or external objects.)

The stator core loss estimate has been validated through experimental measurements on toroidal samples and full size stator laminations. The lamination bonding process increases the core loss of Fe-Co-V material by a factor of 1.2.

A modular, single-phase winding pattern increases the robustness and power density of the system by enabling single-phase inverter drives. The stator winding process and insulation have been successfully demonstrated through a mockup stator winding.

High power density electric machine for turboelectric propulsion. Perreault 2023.

The team introduced a new model for Halbach array rotors, offering a computationally efficient alternative to FEA during the design process. The Halbach array rotor eliminates the need for rotor back iron. Instead, a light-weight titanium rim is used to retain the permanent magnets. The model matches FEA and experimental data within 5%. The model is simple, easy to use, and easy to adapt to different machine toplogies.

Electric Machine Design Specifications

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.

Spakovszky and members of his team, along with industry collaborators, will present their work via a set of five papers at a special session of the American Institute of Aeronautics and Astronautics – Electric Aircraft Technologies Symposium (EATS) at the Aviation conference in June.

The MIT team is composed of faculty, students, and research staff from GTL and the MIT Laboratory for Electromagnetic and Electronic Systems: Henry Andersen Yuankang Chen, Zachary Cordero, David Cuadrado, Edward Greitzer, Charlotte Gump, James Kirtley, Jr., Jeffrey Lang, David Otten, David Perreault, and Mohammad Qasim, along with Marc Amato of Innova-Logic LLC. The project is sponsored by Mitsubishi Heavy Industries (MHI).

As designed, the MIT electric motor and power electronics are each about the size of a checked suitcase weighing 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, 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.

To mitigate risk, the team has built and tested each of the major components individually, and shown that they 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, they say 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 envision 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.

Resources

Paper: "Design and Manufacturing of a High-Specific-Power Electric Machine for Aircraft Propulsion"

Paper: "A Megawatt-Class Electrical Machine Technology Demonstrator For Turbo-Electric Propulsion"

Paper: "Design and Optimization of an Inverter for a One-Megawatt Ultra-Light Motor Drive"

Paper: "Novel Channel-type Heat Exchanger for a Megawatt-Class Integrated Motor Drive Technology Demonstrator"

Paper: "High Speed Rotor System for a Megawatt-Class Integrated Motor Drive Technology Demonstrator"

Posted on 10 June 2023 in Aviation & Aerospace, Electric (Battery), Market Background, Motors | Permalink | Comments (0)