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.
It seems to me that 'counter pumping' seals could work here, as is used on many automotive shaft work and with no contamination mechanism = no fail mode?
You could use a magnetic coupling to allow a true static seal. It's reasonably common in light-to-medium duty pumps for the same reasons around leakage, but there are limits on the transferable torque.
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.
I'm not sure. Could be cost. It might also be that they need time to test or even redesign to use the new fluids if they have different specs. Another possibility is that no matter what the fluid, if it breaks down or evaporates, the loss of insulation could still lead to a fire by igniting other things, such as the pole or nearby vegetation.
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.
You're probably correct about the design, so that would be a question of retrofitting existing old hardware. The example you're giving shows that the transition to these new fluids is already there. Thanks!
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.
It seems to me that 'counter pumping' seals could work here, as is used on many automotive shaft work and with no contamination mechanism = no fail mode?
Extremely high value analysis! Probably why we aren't seeing an announcement for a motive product release.
You could use a magnetic coupling to allow a true static seal. It's reasonably common in light-to-medium duty pumps for the same reasons around leakage, but there are limits on the transferable torque.
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.
Thanks, I had a look at the datasheets and it seems that I have to upgrade my knowledge. But why are transformers fire still a thing then? Cost?
I'm not sure. Could be cost. It might also be that they need time to test or even redesign to use the new fluids if they have different specs. Another possibility is that no matter what the fluid, if it breaks down or evaporates, the loss of insulation could still lead to a fire by igniting other things, such as the pole or nearby vegetation.
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.
You're probably correct about the design, so that would be a question of retrofitting existing old hardware. The example you're giving shows that the transition to these new fluids is already there. Thanks!
The problem with de-ionised water is that its still really quite corrosive.
Its also not as dialectic as common oils.
Yeah, I would not expect it to be used in this case, but just pointing out that it does exist as a non-toxic, non-flammable option.