Founded by engineers from University of Wisconsin-Madison, a company has just appeared claiming to have a route to 13kW/kg electric motors for flight.

H3X-motor-translucent-other-contrast

“For long-distance electric aircraft to be feasible, substantial improvements need to be made to electric propulsion system technology,” according to the company, named H3X. “ARPA-E has determined that for a Boeing 737 to complete a typical five hour flight, the propulsion system must be >12 kW/kg continuous.”

Named HPDM-250, the yet-to-be-made motor is projected to produce 200kW continuously from 15kg. Drive electronics are built-in.

“These specifications are estimates based on electromagnetic thermal and structural simulations. Data from dynamometer will be available Q2 2021,” said HX3.

Figures (see table below) are with a 4:1 reduction gearbox “H3X can design a high torque densisity planetary gearbox that is integrated into the front end cap of the machine to achieve your desire torque peed requirements,” said H3X. “The example 4:1 planetary is based n a real design that is 3kg and 97% efficient.”

• 120Nm peak torque at 360Arms
• 250kW peak
• 30 second peak duration
• 0 – 20,000 RPM
• 95Nm continuous torque
• 200kW continuous
• 96.7% peak motor efficiency
• 99% peak inverter efficiency
• 95.7% peak combined efficiency
• up to 800V dc bus
• 15kg mass
• 6.75 litre volume

Not much about the motor design is public – its data sheet has to be requested – but H3X said that part of the weight reduction comes from its stator coil which is additively manufactured from pure copper with >93% IACS (international annealed copper standard) conductivity, achieving >70% copper fill factor in the HPDM-250.

Primary near-term applications for this motor, said the company, are urban air mobility, EVTOL, UAVs, “military jets and select regional aircraft markets. Primary long-term applications: large commercial electrified aircraft, such as the Boeing 737.”