Electric motor design claims remarkable improvements • Hacker News Board

Re: Electric motor design claims remarkable improvements

#101

Post by tgtweak » Sat, Aug 10, 2019, 6:18 PM UTC

nullwasamistake wrote: post #80

This reads like BS. They mention increases in efficiency like it matters when electic motors are already ~95% efficient. They mention cogging as a problem, when everyone solved that a decade ago by using FOC drivers. It does field weakening by physically rotating part of itself? That doesn't sound like a good idea. At all. A single reduction gear is complex and heavy? Uh no, its probably the cheapest part of the moto…

I think that those "95% efficient" motors are not 95% efficient at all speeds and loads. From what I can grasp, the variable configuration of the rotors let's them trade speed and torque without any loss in efficiency by changing the energizing patterns in the controller. The reduction gearbox is pretty simple in design but it adds one extra component to fail, and it adds weight.

I'm curious to see if they can make the controller simple (cheap, reliable, efficient) - that seems to be the next immediate challenge.

Cool project for sure, the patents have a fair bit of good information on them. They also have a functioning prototype which is good for a company at this stage. See 60 seconds in here: https://youtu.be/yqIKZGx-06Y

I think waiting two years to get them into a car is a bit of a miss in terms of roadmap.

Re: Electric motor design claims remarkable improvements

#102

Post by mikeash » Sat, Aug 10, 2019, 6:25 PM UTC

dzhiurgis wrote: post #100

mikeash wrote: post #86

Earlier quoted context omitted.

Right, look at the size of the motor versus the size of the batteries in an electric car. Efficiency is already well over 90%, too. If you managed to create an idealized electric motor that was 100% efficient, had no limits on power, torque, or RPM, weighed nothing, took up no space, and cost nothing, it would be a nice improvement but I don't think even this would revolutionize electric cars. Batteries are the key.

While motor efficiency is 90%, drivetrain is less than that because of gearbox. This motor claims to remove this inefficiency.

Tesla claims that their drive unit (which includes the motor, inverter, and gearbox) efficiency on their latest models is 93%.

Re: Electric motor design claims remarkable improvements

#103

Post by hwillis » Sat, Aug 10, 2019, 6:25 PM UTC

blattimwind wrote: post #82

hwillis wrote: post #55

Earlier quoted context omitted.

What you're describing[1] is only true for fixed-voltage controllers. With a real driver, all motors will behave as I described, even induction motors[2]. The only caveat is that due to saturation and hysteresis there are obvious nonlinear regions where speed or torque can't be increased. Between those two regions, all motors are capable of constant power output. Air-core motors are in theory more ideal, but good luc…

You seem to misunderstand. Let's talk about an 15 kW asynchronous machine with two poles hooked up to a VFD. At nominal voltage (say 400 V) and nominal frequency (say 50 Hz) it will produce approx 50 Nm of torque to reach its nominal power (n ~ 2900 min^-1). Input current will be somewhere around 30 A. Let's say we want it to run at approx 300 min^-1, thus frequency is reduced to ~5 Hz and voltage to ~40 V. Output to…

Sure, there are lots of ways you can make a motor that will mess that up. You can put in current-limiting fuses. Many motors cool themselves with fans, so they can dissipate lots of heat at speed and will just burn up if you try to add torque. You can make windings with insulation that breaks down at low voltage so the motor can't spin fast.

For big stationary motors that are wound for high voltage, the large number of turns means copper losses dominate and limit torque at all but the highest speeds. Nevertheless, those motors can be rewound for lower resistance, which will cause them to have more even tradeoffs at different voltages/currents. Rewinding a squirrel cage rotor is... a bit of a task, obviously, but the torque/voltage constants are always pretty interchangeable.

Re: Electric motor design claims remarkable improvements

#104

Post by hwillis » Sat, Aug 10, 2019, 6:36 PM UTC

guntars wrote: post #95

magicalhippo wrote: post #83

Earlier quoted context omitted.

In the Fully Charged episode[1] linked in a recent thread here about some guy in Amsterdam making electric cars and boats, the guy mentions that the motors have brushes. I was mildly surprised as I just assumed they'd be brushless DC motors. Are they just efficient enough that the cost/simplicity outweighs going brusless? Or are there other advantages to using brushed motors for electric vehicles? [1]: https://www.yo…

Perhaps it’s simpler and more efficient speed control circuitry. For a DC motor you just need to step down the DC voltage from the batteries. For a brushless motor you basically need a variable frequency inverter that’s necessarily going to be more complex and possibly less efficient.

Yep, mainly. You still need basically the same circuitry, but 3x simpler- you only need one phase instead of three. However you still need the same PWM-type controller to do it. The single phase can operate at several times lower speed though, which makes the output devices and gate drive much cheaper.

Re: Electric motor design claims remarkable improvements

#105

Post by rbanffy » Sat, Aug 10, 2019, 6:45 PM UTC

hyperbovine wrote: post #97

mikeash wrote: post #86

Earlier quoted context omitted.

Right, look at the size of the motor versus the size of the batteries in an electric car. Efficiency is already well over 90%, too. If you managed to create an idealized electric motor that was 100% efficient, had no limits on power, torque, or RPM, weighed nothing, took up no space, and cost nothing, it would be a nice improvement but I don't think even this would revolutionize electric cars. Batteries are the key.

Amdahl’s law of EVs.

Wouldn't that be with multi-motor EVs? ;-)

Re: Electric motor design claims remarkable improvements

#106

Post by rbanffy » Sat, Aug 10, 2019, 6:53 PM UTC

wingspar wrote: post #96

hedora wrote: post #94

Earlier quoted context omitted.

Yeah; my old GMC had a carburetor and the fuel economy is the same as the current replacement, which is the same size, runs half the cylinders (unless it needs all 8) re-levels into aerodynamic mode at speed, and has shutters that close the radiator grill when possible. (The new one is fuel injected, etc). I’m not sure what fuel injectors and electronic ignition got the industry, but it wasn’t real world fuel economy…

I think a big driver for fuel injection and electronic ignition was reliability and meeting emissions standards. Old style carburetor and mechanical ignition regularly required ‘real’ tune-ups and had horrible tailpipe emissions.

I'm also pretty sure the average sedan does 0-60 in the same time a 70's supercar. A BMW 330i can do it in 5.8 seconds. A Lamborghini Countach did that in between 5 and 6 depending on the model.

A Miura could do that in less than 7 seconds. And then would burst into flames ;-)

Re: Electric motor design claims remarkable improvements

#107

Post by adammunich » Sat, Aug 10, 2019, 7:17 PM UTC

corodra wrote: post #53

Don't get me wrong, I saw the title and was excited. I want this to be real. I want to believe. But way too many keyword drops. Disruptive is what red flagged me the most. Way too many promises. Only lab results and "experts" commenting that it should work in theory. But no prototype? Even though it's a different motor they don't "believe" it's going to cost more to make than traditional motors? Only 3d renders? I th…

I've learned a great deal about motors over the years. I don't doubt what they have here is real, as, these principles have been known for a long time.

The reason we don't use permanent-magnet synchronous motors like this in cars though, is because rare earth magnets are much more expensive, and more fragile, than using synchronous reluctance motors which are mostly iron.

The auto companies aren't dumb --if they thought PMS motors were cost effective, they would have been using them by now.

Re: Electric motor design claims remarkable improvements

#108

Post by adammunich » Sat, Aug 10, 2019, 7:19 PM UTC

hwillis wrote: post #79

karmakaze wrote: post #68

Their site[0] has an animation of their 4-pole design and describes some advantages. https://www.linearlabsinc.com/why-our-motor/

There are a number of goofy marketing-wank sections on there. Written by an engineer, but it's got the ring of someone really stretching to sound innovative. > As much as 30% of the typical copper needed is reduced by having all the copper in the coil involved in energy conversion. That's total bullshit. Here's what they're saying: in a typical motor, at least some of the copper will be outside the iron[1]. There's w…

Hello fellow motor nerd!

Re: Electric motor design claims remarkable improvements

#109

Post by adammunich » Sat, Aug 10, 2019, 7:23 PM UTC

dzhiurgis wrote: post #100

mikeash wrote: post #86

Earlier quoted context omitted.

Right, look at the size of the motor versus the size of the batteries in an electric car. Efficiency is already well over 90%, too. If you managed to create an idealized electric motor that was 100% efficient, had no limits on power, torque, or RPM, weighed nothing, took up no space, and cost nothing, it would be a nice improvement but I don't think even this would revolutionize electric cars. Batteries are the key.

While motor efficiency is 90%, drivetrain is less than that because of gearbox. This motor claims to remove this inefficiency.

A reduction gear is really not all that much of a loss, wind on the other hand-- that's a big one.

Re: Electric motor design claims remarkable improvements

#110

Post by adammunich » Sat, Aug 10, 2019, 7:23 PM UTC

xxpor wrote: post #90

mikeash wrote: post #86

Earlier quoted context omitted.

Right, look at the size of the motor versus the size of the batteries in an electric car. Efficiency is already well over 90%, too. If you managed to create an idealized electric motor that was 100% efficient, had no limits on power, torque, or RPM, weighed nothing, took up no space, and cost nothing, it would be a nice improvement but I don't think even this would revolutionize electric cars. Batteries are the key.

According to people on the TMC forums (so take with a grain of salt) Tesla's motors only cost $350-400. If that's true, they're basically perfect already. It's the batteries which drive cost and weight.

They are mostly iron so it seems plausible.