Funny to see the VC money being spent so tangibly and the timeline for creatives, relationships and placements.
It's mostly harmless; companies need to be able to announce products somewhere.
And wasted it. Jalopnik? InsideDevs.com? CNET? Seriously?
I do like the fact that they believe they can do without a transmission entirely, if that works it will save a good bit of energy through weight reduction, mostly during acceleration and deceleration. The bit I don't get is where they talk about DC-DC conversion, most electric cars that I know something about the guts of use tri-phase AC drive.
Making this work across a wide range of scales will be an interesting challenge, in my experience increased torque comes with its own challenges (such as shafts snapping or rotors slipping on or shearing off the mounts of the shaft they are mounted on).
They give a quote on a practical application:
> The resulting Segway enjoyed a 50-percent increase in range, and four times the torque, which boosted the vehicle’s top speed and allowed it to climb a steep 20-percent grade.
If that scales up linearly to electric cars, that's quite a boost.
If that's the case, however, it doesn't really bode well for them, as their efficiency gains will not translate to the high-RPM, high-power motors used in cars. I'm not EE, but I do know that most engineering involves making trade-offs. So I wouldn't be surprised to learn that techniques to improve low-power, low-RPM efficiency probably sacrifices high-power, high-RPM efficiency.
Heat losses come in many forms:
- resistive losses in wiring
- resistive losses in the batteries themselves
(their Ri is nowhere near zero)
- switching losses in the powertrain
- slip losses between the field and the rotor
If a piece of gear does not get its 'advertised performance' that can mean a defective product, deceptive advertising or plainly bad design, or a combination of all of these.
Having a very expensive motor isn't suddenly going to solve any of that, you'll get an advertised range of 15 km while being able to do only 10 and you'll still feel cheated.
I don't feel cheated, I'm just saying that even a modest bump in efficiency could make a big difference to this kind of vehicle, especially if affected both the propulsion and regen side of things.
The observation is this: The faster you draw power from a battery, the less efficient the battery is. Therefore peak shaving goes a long way toward extending battery life. So a motor that is 10% more efficient may increase range by 12%. Or give you the same range with a battery 15% smaller (~100 lbs for some EVs).
Transmissions and converters all result in transmission losses. They're also more components to purchase, install, and maintain. So if they can build a motor that embodies some of those qualities, that's an improvement, even if the resulting motor were slightly less efficient (which they say is not the case).
If an electric car is using three-phase AC, then there's an inverter in there (because batteries do not come with three-phase AC). I don't believe that's as much loss as DC-DC but it's not nothing.
The original Powerwall was DC, so they must have run the numbers and found out the impact was minimal to switch to AC.
For most applications on the order of 2-4%.
This motor has 48 coils, and the ability to change what order and groupings they get powered. Doesn't that change the current substantially without altering voltage? I don't think you would ever run one coil alone, but that leaves at least 9 other patterns where all coils fire evenly.
And what is 'battery voltage'? Battery voltage is something like 2.8 volts, and that's not consistent across all cells at all levels of charge. Any voltage higher than that is due to composition. From what I recall, recharging multiple cells in series leads to some pretty big problems when some of the cells are aging faster than others. Being hard-wired is not a given.
With 48 coils on the motor and a battery pack of 120 or more cells, there are a lot of voltages and currents you could run through the system by reconfiguring instead of inverting.
Ok, great, so now you have a bunch of discrete speeds you can run the motor at. How smooth a ride do you think that's going to provide?
If you can't run a motor at any arbitrary speed within its range, it's useless for any kind of vehicle.
>And what is 'battery voltage'? Battery voltage is something like 2.8 volts
No, that's cell voltage. A battery is a group of cells. That battery in your car that produces 12V is a group of 6 cells each producing 2V, with the cells all connected in series. As I understand it, Tesla batteries are rather high-voltage.
>From what I recall, recharging multiple cells in series leads to some pretty big problems when some of the cells are aging faster than others.
Yet somehow it works just fine for car batteries over the last 100 years, and for most every other battery we use these days (laptops, etc.).
>With 48 coils on the motor and a battery pack of 120 or more cells, there are a lot of voltages and currents you could run through the system by reconfiguring instead of inverting.
Yeah, again, if you just want to run at various discrete speeds. How many people are going to want a herky-jerky car like that?
And you're giving so much salt back that I have to ask, do you believe they are lying? If so then don't beat around the bush. Just say it. You think they are frauds.
> Yet somehow it works just fine for car batteries over the last 100 years, and for most every other battery we use these days (laptops, etc.).
Every time I've replaced my car battery, it's been because one cell failed after I let it deep discharge. Except once where 2 cells failed.
I thought Tesla did something more sophisticated with their packs, but I'm looking at a picture here and there are for sure ~40 cells wired in series. At best there are 4 batteries per array (or they may be connected on the back side). But you don't have to use that bus architecture. It's mechanically simpler and more robust. It's the default. But it's a compromise, favoring physical robustness for reduced chemical robustness. Some day I hope to see other solutions, perhaps like what I described.
Also, I'm giving a lot of "salt back" because I'm an electrical engineer, so I can see how all this stuff is total garbage. You're obviously not. I've even worked on 3-phase "DC brushless" motors and their controllers, so I do know what I'm talking about. This stuff about not needing a DC-DC converter is BS. Of course you don't need a "DC-DC converter" if your motor is AC, which every motor without a mechanical commutator is. You still need some type of power control circuitry to drive the motor; you can't hook it up to a battery!
>Every time I've replaced my car battery, it's been because one cell failed after I let it deep discharge. Except once where 2 cells failed.
If you did a deep discharge, the other cells were degraded too, you just saw the cell that failed first.
>But you don't have to use that bus architecture. It's mechanically simpler and more robust.
Yes, actually you do, unless you want to have ridiculous currents at only 4.2V going to your inverter, which would be stupid because you'd need bus bars and would still have high resistive losses. This is the whole reason we have batteries with series-connected cells instead of parallel-connected cells.
High Torque, Low RPM Motors – Key Enablers of Quiet Flight
High torque gears -> weight
High speed gears -> maintence hassle
It's always been a trade off of fewer compressor stages vs. not having gears. Either of extra compression stages and gears add weight and reduce efficiency, so it's always a tradeoff.
Increasing the torque density compared to the current state-of-the-art would be a big deal for robotics applications.
Aviation is probably the sweet spot application for this motor because decreased weight means increased payload and money. The increased cost is less of a concern than in, say, your cell phone. If you could run the motor without a gearbox and without active cooling, that would save costs in other areas and also decrease maintenance costs.
The "too good to be true" part of aviation is if it, together with battery technology, is able to keep airplanes in the air for a significant amount of time. The high energy density of aviation fuel means that we can build a "good enough" efficiency jet engine by building it like we do today, and just throw fuel at the problem to keep an airplane in the air. With electric propulsion the energy envelope is much tighter and we basically need these miracle solutions in battery tech, motor tech, or both, to make it viable. The presenter's premise was that an airplane that currently takes 180 horsepower to stay in the air, could do the same work with 90 horsepower if the motor and fan were designed differently. Many people are looking at the battery side of the equation, but not many people are looking at the motor side of the equation and there are significant gains to be had here. He then presents evidence indicating that designing a motor and fan differently is possible, and that current turbofan designs are optimized to work with the constraints of jet engines (ie, needing gearboxes to generate enough torque to run bigger and bigger fans).
So more data, more truth, more future
>Torque is the amount of work that a motor or engine produces, typically measured on a per-revolution basis.
No, that's energy, not torque. Torque is rotational force. Torque times rotation is power, which is the rate of work. Work = energy. This is Engineering 101 here; it's inexcusable for the IEEE of all organizations to screw this up. I expect this kind of lousy journalism from a mainstream, layman news outlet like NBC or something, not something aimed at engineers.
>A typical motor’s copper content could be reduced by 30 percent, while generating equivalent torque, they say. So for a given torque level, the HET consumes significantly less energy than competing designs.
Very little of the electrical energy input to a motor is consumed by resistive losses in the windings; almost all of it is consumed by conversion to mechanical energy. Reducing winding resistance is nice, but it's not going to produce some enormous energy savings. Reducing the weight is helpful too, but again, those extra windings are only a fraction of the motor's weight, and unless the motor is being used in an aircraft, motor weight isn't really that big a deal in a vehicle, battery weight is.
>The company’s permanent-magnet tech requires no rare-earth metals.
This sounds like a total crock. Always be suspicious of new inventions when a single invention claims revolutionary advances in more than one field. Magnet technology is separate from motor technology, just like CPU technology is separate from mobile phone technology: it's a very necessary component, but still a component, one which is usually sourced from an outside vendor. Motor manufacturers do not make their own permanent magnets; there's companies that specialize in that. And making magnets with the highest densities of magnetic flux without rare-earth elements would be a pretty big game-changer, so why are they talking about motor windings instead of this?
>The system incorporates a purely electronic transmission
A what? Not possible: a transmission is a mechanical item that converts rotary motion into rotary motion at a different speed and torque level (e.g., high-speed, low-torque into low-speed, high-torque). This is just a meaningless sound bite. Most EVs use transmissions (usually single-speed "gearboxes", not multi-speed "transmissions") because they'd have to make the motor physically larger to generate the torque necessary to drive a car directly, and the extra weight and size isn't worth it; it's easier to drive motors fast and use a gearbox to gear it down, even with the efficiency loss.
>Many electrified vehicles must also integrate a DC-to-DC converter
Again, the "Institute of Electrical and Electronic Engineers" apparently don't understand basic electronics any more. Most EVs use 3-phase brushless motors, or induction motors (Tesla). The motor controllers are driven by DC because that's what Li-ion batteries produce, and they output waveforms to directly drive the windings on the motor in accordance with the current demand for power. I don't see how they expect to get around some sort of controller here.
Sorry, this whole piece sounds like BS. The whole thing is likely some kind of scam to get investor money and then disappear.
> A what? Not possible: a transmission is a mechanical item that converts rotary motion into rotary motion at a different speed and torque level
Other articles about this company explain what this electronic "transmission" is: variable windings. So they can switch from 6 phase to 4 to 3, which will change the RPM per volt. I think.
But I believe this is much less common with lithium ion batteries (~3.6 V/cell) than it was with NiMH (~1.2 V/cell).