C-Motive's electrostatic motors use printed circuit boards instead of magnets
c-motive.com
c-motive.com
Electrolytic capacitors can have far more capacitance than air capacitors. That's the basic concept here.
Here's their patent.[1] Just scroll through the drawings and you'll see how it works.
Here's the key concept: "Numerous aspects of the present disclosure cooperate to increase the breakdown field strength 8406, and / or adjust (e.g. , flatten) the field strength trajectory such as : the permittivity of the dielectric fluid; a selection of fluid constituents to maintain a permittivity profile related to operating temperatures; protection of the dielectric fluid from impurities, presence of water, and / or presence of gases ; providing a surface smoothness of the electrodes 8402, 8404 (or portions thereof), related surfaces, and/ or a housing inner surface ; rinsing / removal of particles and / or impurities (e.g., from manufacturing residue, etc.); provision of a surface treatment on at least a portion of an electrode, and / or on a surface adjacent to the electrode, including varying surface treatments for different electrodes; provision of a coating on at least a portion of an electrode and / or on a surface adjacent to the electrode, including varying the coating for different electrodes; provision of a surface treatment and / or coating on a component at least selectively contacting the dielectric fluid (e.g., a housing inner surface, a packed bed, a side chamber, flow path, and / or eddy region ); protection of composition integrity of the dielectric fluid (e.g., managing materials of bearings, seals , plates , etc. to avoid material breakdown and / or introduction of degradation constituents that negatively affect the performance of the dielectric fluid ); introduction of a field disrupting additive into the dielectric fluid ( e.g., a coated metal oxide, a nano-particle, and /or a conductive particle having a conductor that isolate the conductive particle from physical contact with the dielectric fluid ); introduction of an ion scavenging additive into the dielectric fluid ( e.g., BHT, antioxidants, etc. ); management of gap distance (e.g., using bearings, magnetic separation, a separation assembly, etc.); and / or selected field weakening at certain operating conditions. The utilization of various field management aspects of the present disclosure allows for an increased average field strength in the gap, while maintaining a peak field strength below a breakdown threshold 8406, thereby increasing capacitive energy storage and consequent performance of the ESM 1002."
This thing is sort of like a high voltage electrolytic capacitor with moving parts. They go to a lot of trouble to deal with most of the problems that happen inside capacitors, plus the special problems from moving parts. They had to go all the way to a pumped fluid system with filters, to keep the dielectric fluid cool and clean. Many electric car motors have liquid cooling, so it's no worse than that. It does mean this is probably a technology for larger motors, because the motor requires some accessory systems.
It's not clear that this is a win over magnetic motors, but it's reasonable engineering.
[1] https://patentimages.storage.googleapis.com/cf/eb/f0/6d48f07...
Interestingly, they never mention anything about the need of a pump for the fluid, and claim that their motors are "naturally" sealed.
Are you simply making a joke about permanent magnets?
This is, fundamentally, why electrostatic motors have not seen "power" applications. It's far easier to manufacture a high-tolerance lattice in metals than non-metals. https://ieeexplore.ieee.org/document/1038668
If it's capable of up to about 3000 RPM, and it doesn't weigh too much it could be interesting as an ultralight aircraft power plant.
There's a video with some waves in unlabeled axis. I didn't watch it.
Anyway, it's almost certainly not aimed at aircraft propulsion or power generation. You may want something like it for robotics, but last time a paper from them circulated around here, they seemed to be focusing on instrument actuators and chip fabrication.
"Electric drivetrains" can mean anything from an excavator moving at 5km/h with 3m large wheels in a frequency of less then 0.2Hz up to extreme race RC vehicles, at 100km/h with 5cm wheels at ~100Hz. A car wheels go barely over 1k RPM, but I don't really expect them to do anything useful for those.
I suspect the gap between the plates needs to be kept small to keep forces high (force is something similar to 0.5QV/d), giving high viscous losses that would increase with RPM (proportional?). I suspect that's what eventually limits the speed.
https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=919...
>"C-Motive has designed a sub-5 kW (7 hp) industrial motor platform designed for direct drive applications where high efficiency and high torque lead to substantial operational savings; a 1.5 kW (2 hp) C-Motive machine could save up to $1,400 a year in energy costs in a typical industrial application."
[...]
"A C-Motive electrostatic generator, however, can be connected directly to the hub of the wind turbine and driven directly without an efficiency-robbing gearbox. This can add 20% or more to the annual energy output of the wind turbine..."
That seems like very promising future technology!
Wishing the C-Motive team a lot of luck with their electrostatic generators and electrostatic motors!
A typical 3-phase 2hp industrial motor [1] is over 85% efficient and typical 10:1 reduction gearbox [2] is 94% efficient, which results in about 3kW power usage and 20% power lost to heat, or approx 0.6 kW. If their motor is 100% efficient, used in a 100%-duty-cycle application, in an area with high electrical costs, and with similar reliability to the standard AC motor, this gives $800 or so in savings per year.
In a more typical application with a 50% operating duty cycle and $0.10/kWhr, and guessing at 96% efficiency for their motor, we're down to maybe $200 per year in savings. Larger (>=5hp) motors can be 91% or higher efficiency bringing savings down even more. I can't imagine how C-Motive will equal the reliability, so any extra maintenance could quickly wipe out the savings.
I would guess that a variable-frequency drive (VFD) on the above AC motor, used to control speed and improve the power factor, would have the same efficiency as their motor controller. So I only looked at the AC motor + gearbox versus the C-motive motor + fluid pump.
[1] - https://www.baldor.com/catalog/CEM3558T-5#tab=%22performance... [2] - https://www.bostongear.com/ecatalog?page=product&cid=worm_ge...
They've got something else going on inside the circuitry that lets them manipulate the characteristics of the resulting coil as well to get all the different sounds different traditional pickups get.
I don't have a guitar with the Fishman pickups but have tried them and saw a demo from the Fishman team and talked with the product manager, etc.. I live pretty close to their HQ and they came to a school where I was taking lessons years ago.
Very cool stuff, but the thing is there are other much simpler solutions that don't require a battery or computer in the guitar once people can get out of the mindset of "it must be exactly as Gibson or Fender did it in the 50s." Even Leo Fender had come up with a lot of stuff that was a lot better by the time he died that Fender to this day doesn't use but does get used in say G&L guitars.
The whole nonsense of guitarists thinking "it must be just like Fender and Gibson did it in the 50s" limits the market for both the stuff Leo Fender came up with later and stuff like Fishman's novel pickups.
- weight
- leaks: liquids are always a hassle in things that move. The liquid wants to escape and will do so at the first opportunity.
- serviceability: if there is a leak and a significant loss of fluid, this doesn’t sound like something I can just go pick up at the hardware store like motor oil or hydraulic oil. I’m curious what it is… they simultaneously call it a commodity fluid but also proprietary.
They don't post any specs, but it's supposed to be smaller than traditional motors. If it only needs a small amount to fill small gaps between disks, it might still be lighter than traditional motors. This is especially true if the PCBs are significantly lighter than windings and magnets.
"- leaks: liquids are always a hassle in things that move. The liquid wants to escape and will do so at the first opportunity."
Sure, but this seems like a small concern when we consider that any mobile electric motors require batteries and most of those contain sealed liquid. Even things like bearings in cars are sealed these days.
"- serviceability: if there is a leak and a significant loss of fluid, this doesn’t sound like something I can just go pick up at the hardware store like motor oil or hydraulic oil. I’m curious what it is… they simultaneously call it a commodity fluid but also proprietary."
Sure, if you have an oil leak in your ICE car today, you can't just go get oil, you first have to fix the leak. Don't forget that many transmissions for cars today get filled with "lifetime" fluid and are sealed. This, like the other concerns, is not likely to occur frequently and is consistent with existing paradigms.
I'd be more concerned with what it is rather than it simply being there. Like is it flammable, acidic, caustic, or hazardous in some other way?
In a case of interesting timing, I heard a transformer blow just last week. There wasn't any fire and the fire department wasn't called. The linesmen showed up a couple hours later to replace it.
Its also not as dialectic as common oils.
The reason nobody has used high-power electrostatic motors is that they require high electric fields, which would cause the electric breakdown of air and of most fluids. In contrast, the normal electromagnetic motors use high magnetic fields, which do not cause the breakdown of air, so they do not need immersion in an insulating fluid.
It is likely that the fluid used by them is some kind of fluorinated hydrocarbon, as those have high breakdown fields. Therefore leaks from such a motor are undesirable, so it would be interesting to know how do they prevent leaks between the rotating axle and its bearing. Rotating seals can never be perfect, as the users of Wankel motors must be aware. The main reliability problem of the Wankel motors has also been the rotating seals.
I assume that nobody has tried before to make such motors because nobody has found a way to prevent the leaks until now.
Perhaps the motors are intended to work only with the axle pointing upwards, in which case gravity would prevent the leaks.
No seal is perfect, everything can deteriorate. Why would the seals need to rotate like a Wankel? I think this would be more like the end seals on traditional automotive transmissions. Leaks aren't really that common of a problem there.
There seems to be a lot of different dielectric fluid options. It seems flourinared hydrocarbons are increasingly being replaced by other options. It's possible their proprietary fluid is something else. It would surprise me if their fluid is highly flammable.
tl;dr: concept very old; C-Motive combined incremental improvements