Equipmake announces the world's most power-dense electric motor
We last caught up with Equipmake back in 2018, when this British company's spoked magnet electric motors were capable of generating a monster 9 kilowatts of power per kilogram, using cheap materials and standard manufacturing processes. By comparison, the company says its best permanent magnet rivals are still languishing at around 5 kW/kg.
Now, the company has decided to take advantage of additive manufacturing to see how far they can push this thing, and the results could be revolutionary. Its upcoming Ampere motor is projected to weigh less than 10 kg (22 lb) and make a whopping 220 kW (295 hp) at a sky-high 30,000 rpm, meaning it offers more than 20 kW/kg, making some four times as much power as a similarly sized permanent magnet motor.
All advances in electric vehicle tech must be compared against what Elon Musk is doing as far and away the technology leader in the mass production world. The most recent information we can find from Tesla is from six years ago, so no doubt things have improved, but at that point the Model S motor was making 270 kW (362 hp) at a weight of 32 kg (70 lb). That equates to about 8.4 kW/kg, casting some doubt on Equipmake's claims about its competition, but still, the Ampere motor would effectively be offering more than two and a half times the power output at a given weight. More to the point, it would allow a fairly significant weight reduction to the car. Fitted to an electric motorcycle, the Ampere would be truly frightening, which is exactly how we like things.
Equipmake says the 3D printing technology it's using (in partnership with Bristol-based additive manufacture specialists HiETA) has allowed it to use less metal in its design, combining components into complex shapes that couldn't be achieved with milling or casting, while preserving the spoked magnet design's outstanding cooling capabilities and reducing inertia to allow that crazy-high rotational speed.
The company hopes to have its first prototypes up and running within 12 months, and in the meantime, we can look forward to seeing its regular spoked-magnet motors on the upcoming Ariel Hipercar sometime this year. Light, powerful, torquey and excellent at evacuating heat, they look like seriously impressive motors for high-performance electric vehicles.
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You can have two motors with the same horsepower rating (power). One operates at 3,000 RPM, and the other operates at 30,000 RPM.
The one that operates at 30,000 RPM has 1/10th the output torque as the 3,000 RPM motor of same horsepower.
There is nothing magical or special about this development. Yes, high speed motors need special design, but the holy grail is moving in the other direction......higher torque for the same power output.
There is a limit to a simple, inexpensive gearbox of about 8-13 to one ratio. Current EV motors do not have enough torque output to directly drive wheels on a car. There is a typical 10:1 gear ratio between EV motors and the vehicle wheels. You want to put a smaller 30,000 rpm motor of same power in that vehicle, you now need a 100:1 gear ratio. You are into specialty planetary and other designs....big, expensive and not as robust with contaminates.
This is before discussing the performance differences. Motor inertia is a significant issue in performance...both acceleration and braking. And motor inertia reflects through that gearbox as the square of the gear ratio. So that 30,000 rpm motor, with a 100:1 gear ratio will reflect its rotating inertia by 100^2 = 10,000 times its actual rotor moment of inertia. Not good.
The holy grail is much high torque with smaller or no gearbox.