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Comment by iamgopal | Hacker News Reader

How cooling of rotor being achieved ? Energy, power and torque density of other motor designs are limited by their cooling capacity. Reluctance motor being externally cooled, has this as a prime selling point. I think for claimed improvement, it will need external cooling which is not mentioned in article.

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There's a lot not mentioned. How do they move the rotor magnets in field weakening? How do they reconfigure the coils? How do they get 20 percent more efficiency when most are already over 90-95 percent?

I think they must be claiming a 20% improvement on the 90% baseline, otherwise it doesn't make any sense.

Once again emphasizing the importance of separating between percent and percentage point :P

So, 90% improved to 92%? That's not nothin'...

That's still impossible. 20% of 90% is 18%.

A 20% improvent would be a 20% closer to 100% specifically 20% out of the remaining 10% so 2% overall improvement.

From 90% to 92%

20% less energy dissipated as heat.

I assumed they mean overall efficiency of a vehicle since supposedly it won't be needing a gearbox and the writer of the article is an arsetard.

Not that it’s what’s going on here, but as an aside: it’s possible to get over 100% efficiency, so long as you can take from the environment to achieve it. Reverse-cycle air conditioners routinely get 300–400% efficiency when heating, because they’re moving heat that already exists, rather than generating new heat.

As a layman, how it sounds to me is that your 90–95% figure is the optimal efficiency, but electric cars don’t spend most of their time driving their motors at the speeds that yield this optimal efficiency; this motor, then, has a wider range of speeds at which it can be optimal. They’re also taking reduced weight into account. Hence talking about all this in terms of range rather than electrical efficiency.

They probably mean something along the lines of a 20% reduction in losses. Or, they're comparing at an operating point that is far from peak efficiency. Motors can have 70% or lower efficiency when running at low speeds.

If efficiency is 90%, then 10% is waste; cut that by 20%, and your motor efficiency is now 92%. Something like that. There's a lot of ways they can arrange the math, not to mention it's not clear which motor they're comparing to, which makes this kind of claim very vague. They should just state the efficiency they get.

One picture clearly shows a cooling jacket, and the renders look like liquid could flow into the stator the same way the wires do.

Having an outrunner configuration for this motor makes very little sense. It's hard to cool and power, and magnets are generally powerful enough to produce excess flux in the iron. Their field weakening would also work better with an inrunner since you could do it entirely electronically, and it would be easier to manufacture.

Just curious, if heat is such a limiting factor, why does electric vehicles typically not make use of a regular air intake in the front grill?

I imagined that cooling wasn't that much of an issue since they don't seem to prioritize it a lot.

(I get that there are other factors, but regardless they feel they have the luxury to do without it)

An electric motor is drastically more efficient than an internal combustion engine and so produces much less heat, but it's more difficult to get the heat out of the motor. You don't need a big radiator with lots of airflow to cool an electric motor, but you do need an intelligently designed heat exchanger in the motor unit.

They still have intakes and radiators, maybe just not quite as large. Plus it seems to be stylish to put giant grilles and even fake vents on some cars nowadays.

Here's a great video showing the Chevy Bolt's cooling and heating systems:

https://m.youtube.com/watch?v=_ILkLUE3Zxc

This channel has some awesome, in-depth videos. There is a whole series going over the Bolt's components, including the drive unit and battery.

Model 3 video on cooling the pack.

https://www.youtube.com/watch?v=WU-u-tUjsXo

I think their power density claims must be comparing to the power density of a motor plus gearbox.

"It's easy to cool, at least the stator is, because you can run liquid cooling inside the copper coils."

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