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Electric motor design claims remarkable improvements

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Re: Electric motor design claims remarkable improvements

#21

Post by chrismorgan »

phkahler wrote: post #5
iamgopal wrote: post #3

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.

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?

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.

Re: Electric motor design claims remarkable improvements

#22

Post by spacenick88 »

Svip wrote: post #20
yholio wrote: post #8

Electric cars don't usually have "gearboxes" proper. They use gears, fixed ratio reductors. This is not expensive nor is it fragile nor bulky nor inefficient. The benefits that a very high torque motor could bring are real but marginal, a few percentage points improvements on the respective metrics. They could instantly be negated by, say, the lower initial reliability of a revolutionary design.

I am genuinely curious, why aren't there transmissions for electric engines? Surely the advantage would be the same as for an IC engine. I remember hearing that Tesla tried to build a 2 speed transmission for their Roadster back in the day, but apparently it kept breaking, so they stuck with no transmission. Are there transmissions out there for EVs, and I just haven't been paying attention? And if no, why is it so h…

Afaic the upcoming Porsche Taycan has a two speed transmission. In the Taycan it's used for more efficiency at >160 kph or so something an American car really doesn't need and it costs them a slower 0-100 kph. Tesla uses another trick to get better acceleration to 100 kph. They have two motors and one is geared for high efficiency at US highway cruising speeds (so ca 120 kph).

In general electric motors have a very wide band of excellent efficiency and an even wider band of great efficiency and they are orders of magnitude more efficient than ICE in any part of their operational torgue/speed range.

Re: Electric motor design claims remarkable improvements

#24

Post by tjoff »

iamgopal wrote: post #3

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.

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)

Re: Electric motor design claims remarkable improvements

#25

Post by jdietrich »

tjoff wrote: post #24
iamgopal wrote: post #3

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.

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.

Re: Electric motor design claims remarkable improvements

#26

Post by magicalhippo »

Svip wrote: post #20
yholio wrote: post #8

Electric cars don't usually have "gearboxes" proper. They use gears, fixed ratio reductors. This is not expensive nor is it fragile nor bulky nor inefficient. The benefits that a very high torque motor could bring are real but marginal, a few percentage points improvements on the respective metrics. They could instantly be negated by, say, the lower initial reliability of a revolutionary design.

I am genuinely curious, why aren't there transmissions for electric engines? Surely the advantage would be the same as for an IC engine. I remember hearing that Tesla tried to build a 2 speed transmission for their Roadster back in the day, but apparently it kept breaking, so they stuck with no transmission. Are there transmissions out there for EVs, and I just haven't been paying attention? And if no, why is it so h…

Electric motors full torque regardless of RPM, unlike an ICE which has the usable torque in a limited RPM range.

Re: Electric motor design claims remarkable improvements

#27

Post by hwillis »

iamgopal wrote: post #3

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.

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.

Re: Electric motor design claims remarkable improvements

#28

Post by hwillis »

LargoLasskhyfv wrote: post #14

Uhm. *Halbach Cylinder" like in [1] https://en.wikipedia.org/wiki/Halbach_array ?

No, doesn't look like. Halbach arrays use magnets in different directions to smoothly redirect a field; you can do the same thing with iron or soft steel. Since the field on the back side of the magnets is basically static it doesnt cost any efficiency and its much cheaper. Halbach arrays are sometimes used in motors that need to be very light, like very specialty high-acceleration brushless motors.

Re: Electric motor design claims remarkable improvements

#29

Post by bArray »

codeflo wrote: post #12
bArray wrote: post #6

Feel free to educate me... > The HET is a three-dimensional, circumferential flux, exterior > permanent magnet electric motor with some interesting > characteristics. For starters, it runs four rotors where other motors > typically run one or two. The stator is fully encapsulated in a four > sided "magnetic torque tunnel," each side having the same polarity, > ensuring that all magnetic fields are in the direction of…

I agree about the article, I just want to mention that improving motor efficiency would also help with some of the other losses you mention. Going from 80% to 90% means that you need half as much cooling, batteries may be more efficient when you draw less power from them, etc. That might it worth it even if the motor efficiency gain alone doesn’t look like much on paper.

> Going from 80% to 90% means that you need half as much

> cooling

At the very most this will be 90% isn't all heat, I imagine the amount of cooling required to stay roughly the same.

> batteries may be more efficient when you draw less power

> from them, etc.

From memory, a switch mode power supply is one of the most efficient at about 90% - but you really have to design it well to get that kind of efficiency [1]. The batteries were a soft point for cars. But there's quite a bit of efficiency to get from phase control algorithms which would be in the motor control circuit.

[1] https://en.wikipedia.org/wiki/Switched-mode_power_supply

Re: Electric motor design claims remarkable improvements

#30

Post by yholio »

IshKebab wrote: post #23
yholio wrote: post #15

Earlier quoted context omitted.

And then goes on to make outlandish claims about the benefits of the technology

Also true, but I didn't say otherwise.

Meanwhile, I logically built on the same point to present a contrarian opinion, so your initial reply is somewhat pointless nitpicking. It's exactly what the author of the article intended, making a passing reference to the fundamental flaw thet invalidates the rest of the hype contained. It's not even a conspiracy, it's standard clickbaity journalism, a balanced article about a possible 3% efficiency boost would not make it to HN front-page.
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