How about a 2000V VFD 0.5HP motator?

[freebeard]

spectrum.ieee.org: Electrostatic Motors Reach the Macro Scale

It turns out that Benjamin Franklin was on to something in 1747

For this quest he and his team found inspiration in a lesser-known accomplishment of one of the United States’ founding fathers. “The fact is that Benjamin Franklin built and demonstrated a macroscopic electrostatic motor in 1747,” says Krein. “He actually used the motor as a rotisserie to grill a turkey on a riverbank in Philadelphia” (a fact unearthed by the late historian I. Bernard Cohen for his 1990 book Benjamin Franklin’s Science ).


C-Motive’s 360-watt motor has a half dozen each of rotors and stators, shown in yellow in this cutaway illustration. C-MOTIVE TECHNOLOGIES

[Piotrsko]

Think the gaps are too small for 2Kv, even in a vacuum, it should just arc unless there's thick HV insulation on those plates.

[freebeard]

The actual article:

The machine would be feeble if the dielectric between the charges was air. As a dielectric, air has low permittivity, meaning that an electric field in air can not store much energy. Air also has a relatively low breakdown field strength, meaning that air can support only a fairly weak electric field before it breaks down and conducts current in a blazing arc. So one of the team’s greatest challenges was producing a dielectric fluid that has a much higher permittivity and breakdown field strength than air, and that was also environmentally friendly and nontoxic. To minimize friction, this fluid also had to have very low viscosity, because the rotors would be spinning in it. A dielectric with high permittivity concentrates the electric field between oppositely charged electrodes, enabling greater energy to be stored in the space between them. After screening hundreds of candidates over several years, the C-Motive team succeeded in producing an organic liquid dielectric with low viscosity and a relative permittivity in the low 20s. For comparison, the relative permittivity of air is 1.

[Piotrsko]

Well, sorry..... nothing in the picture or article demonstrated a fluid flow path unless they inject it through the bearing races, and I don't see a seal on the encoder end or an output port. Sealed low hp, low duty cycle could be practical, but I want to see a viable 25 hp version dealing with cooling the "special fluid"

Btw my turkey rotisserie is 1/8 hp

[freebeard]

Sealed low hp, low duty cycle could be practical

I saw more use for robot limb joints than as a prime mover. My concern [should I care] would be shear stress.

Shear Stress in Fluids: Definition, Examples, Application
Shear stress likewise has a substantial impact on the wall-borne fluid friction, resulting in heating, corrosion, and wear-down of surfaces in contact with the flowing fluid. Awareness of these mechanisms informs the design of materials used in piped systems, optimising their durability and lifespan.

[Piotrsko]

Interesting concern about the shear forces. I was going on using some sort of steel, now I wonder how abrasive the dielectric could possibly be. Case hardened steel is somewhat magnetic.

Fractional hp for robot joints? Much rpm and gear reductions , then.

[freebeard]

Quoting the article again:

C-Motive’s motor uses nonconductive rotor and stator disks on which have been deposited many thin, closely spaced conductors radiating outward from the disk’s center, like spokes in a bicycle wheel. Precisely timed electrostatic charges applied to these “spokes” create two waves of voltage, one in the stator and another in the rotor. The phase difference between the rotor and stator waves is timed and controlled to maximize the torque in the rotor caused by this sequence of attraction and repulsion among the spokes.

The "Precisely timed electrostatic charges" is why I characterized it as a Variable Frequency Drive.

[Piotrsko]

Vfd would have more to do with rpm. Hmmm wires instead of discs. Hmmm.

[freebeard]

IIRC VFD enables forward/reverse in software. Something like a stepper or selsyn motor.

What it's about is controlling crankshaft rotation.