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.
I wish they had some examples of what RPM, torque, weight, and size specs were for a few possible applications. They seem to emphasize low RPM, but is that 200 RPM or 2000RPM? With other electric motors being capable of 10k-20k RPM, the "low" RPM mention is very vague.
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.
It's an electrostatic motor, so expect peak performance at close to 0 RPM. It probably won't work well at 1k RPM, but whether "too high frequency" for it is closer to 10 RPM or 100 RPM isn't clear.
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.
Their applications pages mentions wind turbines and automotive applications and promises increased efficiency vs conventional motors. That would require maintaining 90%+ efficiency at well over 1k RPM. But no specs anywhere, so hard to tell whether this is real.
TBH, I didn't think about low rotational speed wind turbines. Yeah, it may be a big thing for those.
"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 don't think it was really for automotive applications. It said something like "low speed vehicles". Made me think of something like golf carts or maybe ATVs. Of course without a gearbox, the biggest factor would be what wheel diameters are used since that would be the main ratio with revs per mile.
I've long wondered if there's a possible application for something like this using 3d printing and electrets. Basically you can freeze an electric field inside of an insulator if you apply it as the material solidifies. I think you should be able to embed electrets inside of 3d prints simply by generating a strong electric field at the print head or slightly behind it. You can also vary the field and embed a 3d electret that can act as, say, a sensor or a hidden ID in the print.
I’ve been doing pcb design around sensor coils for capacitive sensing. My engineering team has been playing with similar ideas around printing coils for other electro magnetic purposes. Motors are an obvious usecase. Good to see others doing similar stuff with printed circuit boards. It takes a way a lot of complexity and pcb processes have some pretty good precision these days.
I'm fairly ignorant about motor design, but my immediate thought was "isn't this going to exert pulling forces on the PCB traces?". Seems like that would limit how much torque your motor can exert? Which I guess isn't necessarily a problem for many applications.
The forces are pretty much shear forces in the plane of the PCB, which traces can handle reasonably well. Also, the amount of force per trace is very small - the motor only has significant torque because there are many traces per PCB multiplied by many PCBs.
I recall watching Carl Brugeja on YouTube some years ago making tiny motors using PCB for the coils, like this[1] for example. Like you say idea is hardly groundbreaking, but there's a lot of details to optimize as with any non-trivial engineering project.
Fishman has been doing these with guitar pickups for several years now. It's supposed to allow for greater consistency and also make it possible to do some stuff that couldn't be done with an actual coil of wire.
I think they use it to change the number of coils that are active in the pickup. I think this is outside of/as well as supporting existing features like coil tapping humbuckers.
Whatever they are using, it is absolutely necessary.
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.
Not the person you asked but there’s a few reasons off the top of my head:
- 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?
The dieletric oil in transformers is both toxic and flammable, causing a lot of damage when they start burning. If an alternative, safer fluid existed it would be a massive market.
I guess it depends on what dielectric constant they need and the serviceability. Even deionized water can be a dielectric. I think Novec makes multiple non-toxic non-flammable dielectric too.
>"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!
The C-Motive guys have PR all over the web.
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...
I wish they had some examples of what RPM, torque, weight, and size specs were for a few possible applications. They seem to emphasize low RPM, but is that 200 RPM or 2000RPM? With other electric motors being capable of 10k-20k RPM, the "low" RPM mention is very vague.
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.
It's an electrostatic motor, so expect peak performance at close to 0 RPM. It probably won't work well at 1k RPM, but whether "too high frequency" for it is closer to 10 RPM or 100 RPM isn't clear.
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.
Their applications pages mentions wind turbines and automotive applications and promises increased efficiency vs conventional motors. That would require maintaining 90%+ efficiency at well over 1k RPM. But no specs anywhere, so hard to tell whether this is real.
TBH, I didn't think about low rotational speed wind turbines. Yeah, it may be a big thing for those.
"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 don't think it was really for automotive applications. It said something like "low speed vehicles". Made me think of something like golf carts or maybe ATVs. Of course without a gearbox, the biggest factor would be what wheel diameters are used since that would be the main ratio with revs per mile.
I've long wondered if there's a possible application for something like this using 3d printing and electrets. Basically you can freeze an electric field inside of an insulator if you apply it as the material solidifies. I think you should be able to embed electrets inside of 3d prints simply by generating a strong electric field at the print head or slightly behind it. You can also vary the field and embed a 3d electret that can act as, say, a sensor or a hidden ID in the print.
Previous discussion 2 months ago: https://news.ycombinator.com/item?id=41309292
A lot of blabla, no technical data. Suspicious.
Some more technical content (literature review, but includes the university work this spun out of) if the sales page isn't doing it for you:
https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=919...
I’ve been doing pcb design around sensor coils for capacitive sensing. My engineering team has been playing with similar ideas around printing coils for other electro magnetic purposes. Motors are an obvious usecase. Good to see others doing similar stuff with printed circuit boards. It takes a way a lot of complexity and pcb processes have some pretty good precision these days.
I'm fairly ignorant about motor design, but my immediate thought was "isn't this going to exert pulling forces on the PCB traces?". Seems like that would limit how much torque your motor can exert? Which I guess isn't necessarily a problem for many applications.
The forces are pretty much shear forces in the plane of the PCB, which traces can handle reasonably well. Also, the amount of force per trace is very small - the motor only has significant torque because there are many traces per PCB multiplied by many PCBs.
I recall watching Carl Brugeja on YouTube some years ago making tiny motors using PCB for the coils, like this[1] for example. Like you say idea is hardly groundbreaking, but there's a lot of details to optimize as with any non-trivial engineering project.
[1]: https://www.youtube.com/watch?v=oa6sP-joAr8
Fishman has been doing these with guitar pickups for several years now. It's supposed to allow for greater consistency and also make it possible to do some stuff that couldn't be done with an actual coil of wire.
Electrostatic microphones have been a thing for a long time, so that's not unexpected. But it's not a power application.
What kind of stuff? Isn't just everything possible with FOC on BLDC motors?
I think they use it to change the number of coils that are active in the pickup. I think this is outside of/as well as supporting existing features like coil tapping humbuckers.
Not a big fan of the dielectric fluid these motors have to be filled with.
Whatever they are using, it is absolutely necessary.
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.
There are new dielectric refrigerants that aren’t as polluting, but they’re more expensive
"Rotating seals can never be perfect,"
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.
Extremely high value analysis! Probably why we aren't seeing an announcement for a motive product release.
Why?
Not the person you asked but there’s a few reasons off the top of my head:
- 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.
"- weight"
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?
The dieletric oil in transformers is both toxic and flammable, causing a lot of damage when they start burning. If an alternative, safer fluid existed it would be a massive market.
I guess it depends on what dielectric constant they need and the serviceability. Even deionized water can be a dielectric. I think Novec makes multiple non-toxic non-flammable dielectric too.
From the page: https://www.c-motive.com/applications/
>"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!
Nice. I like the short paragraph on "Why hasn’t anyone done this before?" at the bottom of the page.
tl;dr: concept very old; C-Motive combined incremental improvements
I found somebody doing single phase electric motor on YouTube:
https://youtu.be/s3yO7jYaD98?si=xecjNpuDaMA0IP1Q