41–50 of 144 posts
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.
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.
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.
I’ve always wondered why no one is researching motors that use electric fields instead of magnetic?
Earlier quoted context omitted.
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 roughl…
Generally speaking, no. P = 2piM*n, while the common types of motor used in electric drives (synchronous and asynchronous three phase machines) will produce nominal torque at (almost) any speed from 0 (not for asynchronous machines) to nominal speed; therefore output power is pretty much proportional to speed.
The only type of motor that comes to mind that has somewhat of a constant-power behaviour to it are series wound motors.
I’ve always wondered why no one is researching motors that use electric fields instead of magnetic?
There are electrostatic motors, it's just that they aren't particularly interesting (low power density, very high drive voltages, poor efficiency). They do have one interesting property, which is that at zero speed they can develop nominal torque without using any power (unlike say a synchronous servo).
Earlier quoted context omitted.
> 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.
Also, a single stage spur or helical reduction has ~99% efficiency[2]. It's not at all like a full transmission[3], which has a ton of parts that are always spinning and churning oil, plus sliding friction. The reduction on an electric motor uses a more efficient grease and does not churn oil. Fun fact- greases (mixes of soap and oil, normally silicone oils) are non-newtonian fluids. They're shear-thinning, like ketchup, and have much lower friction under pressure while still sticking in place, unlike oil. Amazingly sophisticated for something that has existed for centuries!
Anyway, what I'm saying in the above post is that even if the efficiency is much higher, even counting the gearing, it does not necessarily lead to higher efficiency elsewhere in the car. If this motor gives 20% improvement on an 85% efficient motor+gearset, that's only a 3.4% decrease (85/88) in power required. Say that 3.4% of power would have been operating in a regime that had 10% higher losses(which would be insane)- that's only .34% in cascading savings. 3.74% total. That decrease will be very, very easily overwhelmed if the motor requires higher current or is otherwise less ideal for the drivetrain. Resistive losses alone mean that if the current is 1.85% higher, it will be a net loss.
[1]: https://en.wikipedia.org/wiki/Constant-velocity_joint
[2]: https://khkgears.net/new/gear_knowledge/abcs_of_gears-b/gear...
Earlier quoted context omitted.
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.
Electric motors don't have this particular problem, and they don't need a start gear that is a lot shorter than the other gears (1st to 2nd is usually around a factor two, while from 2nd up to the next higher gear the ratio will change by perhaps 30 % or so) because they can deliver nominal torque at low speeds or from zero speed (so they don't need a clutch, either). An ICE can't do that.
Here are the transmission ratios of a random six speed transmission:
1st 2nd 3rd 4th 5th 6th R
4.2 2.5 1.7 1.3 1 0.8 3.8I’ve always wondered why no one is researching motors that use electric fields instead of magnetic?