An electrostatic motor or capacitor motor is a type of

electric motor An electric motor is an electrical machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a wire winding to generate f ...

based on the attraction and repulsion of

electric charge Electric charge is the physical property of matter that causes charged matter to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative'' (commonly carried by protons and electrons res ...

. An alternative type of electrostatic motor is the spacecraft electrostatic ion drive thruster where forces and motion are created by electrostatically accelerating ions.

Overview

An electrostatic motor is based on the attraction and repulsion of electric charge. Usually, electrostatic motors are the dual of conventional coil-based motors. They typically require a high voltage power supply, although very small motors employ lower voltages. Conventional electric motors instead employ magnetic attraction and repulsion, and require high current at low voltages. In the 1740s and 1750s, the first electrostatic motors were developed by Andrew Gordon and by

Benjamin Franklin Benjamin Franklin ( April 17, 1790) was an American polymath who was active as a writer, scientist, inventor, statesman, diplomat, printer, publisher, and political philosopher. Encyclopædia Britannica, Wood, 2021 Among the leading int ...

. Today the electrostatic motor finds frequent use in micro-mechanical (

MEMS Microelectromechanical systems (MEMS), also written as micro-electro-mechanical systems (or microelectronic and microelectromechanical systems) and the related micromechatronics and microsystems constitute the technology of microscopic devices, ...

) systems where their drive voltages are below 100 volts, and where moving, charged plates are far easier to fabricate than coils and iron cores.

Corona-discharge motor

The corona-discharge motor, also known as corona motor, has been known for centuries.

Nanotube nanomotor

In 2004, researchers at

University of California, Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant un ...

, developed rotational bearings based upon multiwall carbon nanotubes. By attaching a gold plate (with dimensions of the order of 100 nm) to the outer shell of a suspended multiwall carbon nanotube (like nested carbon cylinders), they are able to electrostatically rotate the outer shell relative to the inner core. These bearings are very robust; devices have been oscillated thousands of times with no indication of wear. These nanoelectromechanical systems (NEMS) represent a promising direction in miniaturization and may find their way into commercial applications in the future.

Electrostatic ion drive

Electric motors, in general, produce motion when powered by electric currents. The common type of spacecraft ion thruster uses electrostatic forces to accelerate ions to generate forces to create motion, and thus can be considered as unconventional electric motors. Gridded electrostatic ion thrusters commonly utilize

xenon Xenon is a chemical element with the symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the ...

gas. This gas has no charge and is ionized by bombarding it with energetic electrons. These electrons can be provided from a hot-

filament The word filament, which is descended from Latin ''filum'' meaning " thread", is used in English for a variety of thread-like structures, including: Astronomy * Galaxy filament, the largest known cosmic structures in the universe * Solar filament ...

cathode A cathode is the electrode from which a conventional current leaves a polarized electrical device. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. A conventional current describes the direction in whi ...

and accelerated in the electrical field of the cathode fall to the anode (Kaufman type ion thruster). Alternatively, the electrons can be accelerated by the oscillating electric field induced by an alternating magnetic field of a coil, which results in a self-sustaining discharge and omits any cathode (radiofrequency ion thruster).

Patents

The prime classifications of electrostatic motors by the USPTO are: * Class 310 ELECTRICAL GENERATOR OR MOTOR STRUCTURE ** 300 NON-DYNAMOELECTRIC *** 308 Charge accumulating *** 309 Electrostatic * -- J. Gallegos -- "''Static electric Machine''" * -- E. Thomson -- "''Electrostatic motor''" * -- Harold B. Smith -- "''Apparatus for transforming electrical energy into mechanical energy''" * -- W. G. Cady -- "''Electromechanical System''" * —- T. T. Brown -- "''Electrostatic motor''" (1934-09-25) * -- B. Bollee -- "''Electrostatic Motor''" (''ed.'' Electrostatics from Atmospheric Electricity) * -- B. Bollee -- "''Electrostatic Motor''" * -- MITSUBISHI CHEM CORP -- "''Electrostatic actuator''" * -- Robert, et al. -- "''Electrostatic Motor''"

References

External articles and further reading

* de Queiroz, Antonio Carlos M., "
An Electrostatic Linear Motor
'". 24 January 2002. * William J. Beaty, "

'". * "

'", tm.net. * Fast and Flexible Electrostatic Motors at Univ. Tokyo"

'". * Heavy Lifting Electrostatic Motors at Univ. Tokyo"

'". * E. Sarajlic ''et al.''
3-Phase Electrostatic Stepper Micromotors
{{Electric machines Electrostatic motors, Electrostatics Electric motors