Everyone knows electric airplanes are coming. We just don’t know when. Several short range planes that can carry a few passengers are being tested, but to get electric aircraft that can fly more people longer distances will require better batteries or more powerful motors. The issue when it comes to electric flight is power versus mass.
The startup H3X says it has developed a compact electric motor that develops more than 3 times the power and weighs less than most commercially available motors. To be specific, the company claims its HPDM 250 motor has an output of 13 kW per kg. For aircraft applications, 12 kW per kg is the benchmark the industry is aiming to achieve. According to Tech Crunch, the best production motors today can only offer 3 to 4 kilowatts per kilogram of continuous power. The HPDM 250 is rated at 250 kW of continuous power yet only weighs 15 kg.
How does H3X get so much power from such a small package? While the pieces are similar in some ways to motors and power assemblies available today, the team basically started from scratch with the idea of maximizing efficiency and minimizing size. That meant solving the different cooling issues that pertain to various components of any electric motor.
An electric motor typically has three components — the motor, a power delivery system, and a gearbox. Usually each component has its own housing and they are all bolted together to make one complete system. But the gearbox may not be able to operate at the temperatures generated by the motor or the power system. What H3X has done is integrate all the components into one housing that uses one cooling system.
“No one [else] is targeting the level of performance we’re looking at right now,” Liben says. “We’re not relying on one big tech or something — there’s no magic bullet. There are a few improvements that have very significant gains, like 50% better than the state of the art, and lots of areas that add 10%-20%.”
One of the improvements is using advanced power electronics that can tolerate the higher temperatures inside the common housing. But better cooling techniques are also a factor. Using new pure copper 3D-printing techniques allows more cooling to fit inside the housing and the use of custom internal geometries so the motor, gearbox, and power electronics can all be mounted in the best possible location inside the housing.
Aren’t all these advanced techniques like pure copper 3D-printing expensive? Yes they are, but as Liben explains, the compact size of the complete motor package leads to cost savings in other areas of aircraft design. “People think, ‘3D printing copper, that’s expensive!’ But when you compare it to the super high performance windings you’d need otherwise, and the different ways that you manufacture them, that can require a lot of manual steps and people involves. It can be a lot simpler printing something,” he explains. “It can be counterintuitive, but…..when you’re selling something three times smaller than the other guy, even if it’s high performance materials, it’s actually not as expensive as you’d think. Based on the customers we’ve talked to so far, we think we’re in a good spot.”
Liben is excited about the prospects for the new motor. He admits that electric passenger airplanes that can fly medium range routes are a few years off yet, but thinks the HPDM 250 could open new commercial opportunities for cargo drones, electric boats, and air taxis, all of which could benefit from longer range and higher carrying capacity.
Why are Liben and his colleagues doing this? “The problem was uniquely suited to our abilities, and passions too — we’re excited about this stuff. We care about decarbonization of the different transit sectors, and aviation is going to become a growing part of the global carbon footprint over the next few decades as electric improves ground vehicles.”
An electric motor that is 3 times more powerful for its weight and size could be just what the electric transportation revolution needs to accelerate its forward progress. For more details about the HPDM 250 high power compact electric motor, check out the video below.
Image courtesy of H3X