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Electric motor design claims remarkable improvements

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Re: Electric motor design claims remarkable improvements

#31

Post by bArray »

tinco wrote: post #13
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'm a total novice to electric motor design, but they mention being able to switch between simulating phases. I don't think they mean they do higher torque at lower power input. I think it means that they can transparently trade efficiency for higher torque, so they can be efficient at low torque, high speed, while also be able to deliver torque at low speed without requiring gearing. I know how marketing departments…

Good point and yeah, that would be useful. Getting greater torque without needing gearing would definitely add to efficiency.

Re: Electric motor design claims remarkable improvements

#32

Post by hwillis »

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.

> I just want to mention that improving motor efficiency would also help with some of the other losses you mention.

It's not that simple. Increases in torque are strongly associated with increases in current- torque is directly proportional to total magnetic flux, so more torque in a smaller package generally means more current in your wires. The alternative is to add more turns of thinner wire, but thinner wire has lower packing efficiency.

Losses from current rise as RI^2 in simple wires, slightly faster in transistors, and some very complex factor in batteries that I can't remember but is between I^3 and I^4. You can make a 100% efficient motor, but if it quadruples the current draw then it will be almost useless for vehicles.

Re: Electric motor design claims remarkable improvements

#33

Post by bArray »

natermer wrote: post #17
tinco wrote: post #13

Earlier quoted context omitted.

I'm a total novice to electric motor design, but they mention being able to switch between simulating phases. I don't think they mean they do higher torque at lower power input. I think it means that they can transparently trade efficiency for higher torque, so they can be efficient at low torque, high speed, while also be able to deliver torque at low speed without requiring gearing. I know how marketing departments…

I'm a lay person somewhat familiar with the terminology. I am going to be wrong on several details. What they were talking about is phase weakening. Think of voltage as 'electrical pressure'. Like PSI or Bar. Think of amperage as 'volume per second' or 'amount of electrons (equivalent charge) per second'... like liters per minute. Combine the volume per second by pressure and you get total energy per second; watts. H…

Very interesting, thank you! Do you have more information I can read about phase weakening and BLDC control algorithms?

I ask because I happen to be designing a BLDC motor controller, I am aware of using the back EMF to measure the motor phase, but never considered it as a force slowing the motor down. As a software engineer by trade I was hoping I could perhaps dynamically switch between the two control techniques to get low-end torque and high-end speed? I was also hoping to setup the controller to optimize the various parameters for the specific motor it is controlling by measuring the back EMF.

Any help is greatly appreciated :)

Re: Electric motor design claims remarkable improvements

#34

Post by hwillis »

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…

> Surely the advantage would be the same as for an IC engine.

No. The two types of motor are fundamentally different. Combustion engines need transmissions because they produce relatively constant torque (within 50% of max torque). Electric motors on the other hand produce relatively constant power.

This makes total sense when you think about it. An IC engine is powered by explosions; every explosion produces roughly the same force on the piston regardless of speed. You can't get more power without more explosions because you can't cram more air in the cylinder. You can only speed up the engine.

In an electric motor, you can cram as many electrons into the wires as you want. You are only limited by how much heat is generated. Increasing speed increases heat slower than increasing torque, but you can still basically increase either as much as you want.

Re: Electric motor design claims remarkable improvements

#35

Post by leguminous »

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)

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.

Re: Electric motor design claims remarkable improvements

#36

Post by randallsquared »

Mvandenbergh wrote: post #16
phkahler wrote: post #5

Earlier quoted context omitted.

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.

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

Re: Electric motor design claims remarkable improvements

#38

Post by raxxorrax »

hwillis wrote: post #32
codeflo wrote: post #12

Earlier quoted context omitted.

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.

> I just want to mention that improving motor efficiency would also help with some of the other losses you mention. It's not that simple. Increases in torque are strongly associated with increases in current- torque is directly proportional to total magnetic flux, so more torque in a smaller package generally means more current in your wires. The alternative is to add more turns of thinner wire, but thinner wire has…

But the missing torque necessitates a transmission as the article mentions that will also have a limited degree of efficiency.

Re: Electric motor design claims remarkable improvements

#40

Post by balfirevic »

bArray wrote: post #33
natermer wrote: post #17

Earlier quoted context omitted.

I'm a lay person somewhat familiar with the terminology. I am going to be wrong on several details. What they were talking about is phase weakening. Think of voltage as 'electrical pressure'. Like PSI or Bar. Think of amperage as 'volume per second' or 'amount of electrons (equivalent charge) per second'... like liters per minute. Combine the volume per second by pressure and you get total energy per second; watts. H…

Very interesting, thank you! Do you have more information I can read about phase weakening and BLDC control algorithms? I ask because I happen to be designing a BLDC motor controller, I am aware of using the back EMF to measure the motor phase, but never considered it as a force slowing the motor down. As a software engineer by trade I was hoping I could perhaps dynamically switch between the two control techniques t…

Read this: https://krex.k-state.edu/dspace/bitstream/handle/2097/1507/J...

It's a thesis from James Mavey titled "Sensorless field oriented control of brushless permanent magney synchronous motors".

Other good resources:

http://build-its-inprogress.blogspot.com

http://discourse.odriverobotics.com/

https://things-in-motion.blogspot.com

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