Re: Solar powered electrostatic motor drone ??

I think Philips dabbled with them many decades ago. A report will be somewhere in the Philips Technical Review.

Thanks for that hint. The Philips Technical Review is a treasure trove of interesting stuff.

I found a paper by B. Bollée on electrostatic motors:

I wonder how many orders of magnitude an electrostatic motor is worse than a magnetic motor, in some criterion like power per volume or power per dollar. 6 maybe?

It's not so easy to tell. Electromagnetic motors have benefitted from a long and intense process of optimization, both for performance and for ease of manufacturing. Throwing some ballpark guesses at a possible realization of a 1kW electrostatic motor, I got a motor volume greater than an electromagnetic motor, to be sure, but not hugely so. One or two orders of magnitude perhaps. Certainly not six.

Jeroen Belleman

One source says that "Benjamin Franklin invented the first electrostatic motor in 1748."

The main problem for outdoor use is going to be leakage, I expect.

Could be useful if you forget where you parked your car at the airport. ;)

Cheers

Phil Hobbs

Seems to me that an electrostatic motor will need switching of many kilovolts into the electrodes. Charging and discharging, efficiently.

I was thinking of stacks of many stator disks with conductive sectors, interleaved with as many rotor disks. Running voltage would be a few hundred volts, maybe up to a kV. Commutation can be mechanical or electronic. If fed with AC, commutation is implicit, but some tricks would be needed to create a starting torque.

Leakage in humid condition can be dealt with by covering the disks with an insulating coating. The problem is not so different from magnetic motors.

Jeroen Belleman

Cheers

Phil Hobbs

They just come in pairs.

Since humid air has higher K than dry air such a motor might even run better?

Where did that come from? Why do you think monopoles should be involved?

Jeroen Belleman

Magnetostatics and electrostatics are not the same in our world, because there’s no free magnetic charge (i. e. monopoles) to cause magnetic leakage.

Cheers

Phil Hobbs

Is magnetism quantized?

If you read about the John Chan hysteretic core model in LTSpice, you get the impression that the magnetic flux threading a magnetisable core is quantised, which it sort of is. Magnetisable core materials are broken up into small magnetic domains, and they flip magnetic oerientation on a domain by domain basis.

At a deeper level a magnetic field is just the relativistic consequence of moving electric charges, and since charge is quantised, the magnetic field has to be too, but I doubt if there a minimum increment in magnetic field that can be expressed in very small fractions of a Tesla.

OK, true, but I don't see why that affects the practicality of electrostatic motors. In fact, if you remove the motor drive of a pelletron, it will happily run in reverse, driven by the acccumulated charge on the high-voltage electrode.

(I'm not suggesting that a pelletron is an optimal configuration for an electrostatic motor.)

Jeroen Belleman

I remember, as a child, bringing a magnet slowly towards the input transformer of a sensitive amplifier and hearing the crunching noise as the domains flipped over. It was a source of wonder to me - expecially as I couldn't find anything about it in the textbooks available to me at the time.

There are very big ones at CERN, but the projectiles are tiny...

Jeroen Belleman

One I repaired used a "piezoelectric transformer" in the gun itself, right next to the electrodes. That is much smaller and lighter than the equivalent electromagnetic transformer, so it would also be the obvious choice for a lightweight electrostatic motor.