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PowerPedia:Homopolar generator

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A homopolar generator, also known as a unipolar generator, acyclic generator, or disk dynamo, is a Direct current There was an error working with the wiki: Code[80] passes through the There was an error working with the wiki: Code[81] continually in the same direction.There was an error working with the wiki: Code[1]. The device is electrically symmetricalThere was an error working with the wiki: Code[2], and generates Direct current. Some of these devices also have "homopolar magnets", which have pole pieces arranged around a common centre.

History and development

Faraday Disk Dynamo

The homopolar generator was developed first by There was an error working with the wiki: Code[82] Direct current dynamos and then Alternating current alternators.

Later developments

Long after the original Faraday disc had been abandoned as a practical generator, a modified version combining the magnet and disc in a single rotating part (the rotor) was developed. Sometimes the name homopolar generator is reserved for this configuration. One of the earliest patents on the general type of homopolar generators was attained by Charles E. Ball (US238631 March 1881). Other early patents for homopolar generators were awarded to There was an error working with the wiki: Code[83] and There was an error working with the wiki: Code[84] separately. There was an error working with the wiki: Code[85] and There was an error working with the wiki: Code[86] for their work with homopolar generators. The Forbes dynamo, developed by the Scottish electrical engineer There was an error working with the wiki: Code[87], was in widespread use during the beginning of the 20th century. Much of the development done in homopolar generators was patented by There was an error working with the wiki: Code[88] and There was an error working with the wiki: Code[89].

One of the larger homopolar generators that was produced by Parker Kinetic Designs via the collaboration of There was an error working with the wiki: Code[90], There was an error working with the wiki: Code[91], and There was an error working with the wiki: Code[92]s. Another large homopolar generator was built by There was an error working with the wiki: Code[93] at the There was an error working with the wiki: Code[94]" in these machines.

Description and operation

Magnetism and current

Magnetism can make, or There was an error working with the wiki: Code[95], electric current only when the conductor that carries the current and the lines of magnetic force move so that they cut across each other. The direction in which current flows in the moving conductor can be learned with There was an error working with the wiki: Code[108] for generators.

Disk type generator

The device consists of a There was an error working with the wiki: Code[96] Flywheel rotating in a Magnetic field with one electrical contact near the axis and the other near the periphery. It has been used for generating very high currents at low voltages in applications such as There was an error working with the wiki: Code[109], Electrolysis and There was an error working with the wiki: Code[110] research. In pulsed energy applications, the There was an error working with the wiki: Code[111] of the rotor is used to store energy over a long period and then release it in a short time. There is an uncertain nature of the torque reaction in homopolar machines, though it is known that There was an error working with the wiki: Code[112] and There was an error working with the wiki: Code[113]s are generated in circular homopolar generators.

In contrast to other types of generators, the output voltage never changes polarity. The charge separation results from the There was an error working with the wiki: Code[97]" or There was an error working with the wiki: Code[114], which results in large losses at the low voltages generated. The table below shows the results of different relative motions of the parts of a circular homopolar generator There was an error working with the wiki: Code[5]. A drum type HPG has a magnetic field (B) that radiates radially from the center of the drum and induces voltage (V) down the length of the drum.

Field Rotation Paradox

{| width=100% border="0"

|-

! Magnetic source || Disk || Indicator || Voltage generated

|-

| Stationary || Stationary || Stationary || No

|-

| Stationary || Moved || Stationary || Yes

|-

| Stationary || Stationary || Moved || Yes

|-

| Stationary || Moved || Moved || Undetermined

|-

| Moved || Stationary || Stationary || No

|-

| Moved || Moved || Stationary || Yes

|-

| Moved || Stationary || Moved || Yes

|-

| Moved || Moved || Moved || Undetermined

|}

If the magnetic field is provided by a permanent There was an error working with the wiki: Code[115], the generator works regardless of whether the magnet is fixed to the stator or rotates with the disc. Before the discovery of the Electron and the There was an error working with the wiki: Code[116], the There was an error working with the wiki: Code[117] was inexplicable and was known as the There was an error working with the wiki: Code[118]. The voltage is "undetermined" when both the indicator and the disk are rotated, regardless of whether the magnet is moving. There is an EMF and a nonuniform charge density, but no reaction of the indicatorThere was an error working with the wiki: Code[6]. An electric field is generated, but no voltage is brought out for display. This differs from the different relative motions of the parts of a rectilinear homopolar generator (where the answer would be "No"). The current, once started, may be sufficient to maintain itself and even increase in strength and the device would be operated as a self-excited generator.

Physics

Like all dynamos, the Faraday disc converts Kinetic energy to Electrical energy. However, unlike all other dynamos, this machine cannot be analysed using Faraday's own law of There was an error working with the wiki: Code[119]. This law (in its modern form) states that an electric current is induced in a closed electrical circuit when the magnetic flux enclosed by the circuit changes (in either magnitude or direction). However, the circuit in the Faraday disc is parallel to the magnetic flux vector and therefore encloses no magnetic flux. Therefore, Faraday's law does not apply to this machine.

Instead, the There was an error working with the wiki: Code[120] is used to explain the machine's behaviour. This law, discovered thirty years after Faraday's death, states that the force on an electron is proportional to the There was an error working with the wiki: Code[121] of its Velocity and the There was an error working with the wiki: Code[122] vector. In geometrical terms, this means that the force is at right-angles to both the velocity (azimuthal) and the magnetic flux (axial), which is therefore in a radial direction. The radial movement of the electron then creates an electric current between the centre of the disc and its rim.

There is a subtle difficulty in this explanation, which often leads to a misunderstanding of how the machine works. The key word in the preceding paragraph is velocity, which prompts the question, "velocity relative to what?". If the velocity relative to the magnet is assumed as the cause of the Lorentz force, then the explanation contradicts There was an error working with the wiki: Code[123], which states that it is impossible to tell whether a uniform magnetic field is moving or stationary. This assumption would also imply that rotating the magnet and not the disc would cause a current to flow, which is not what experimenters have found.

The correct interpretation of the velocity of the electron is that it is relative to the static parts of the machine, which are the sliding contacts and the circuit to which they are connected. In the language of special relativity, these objects act as the 'There was an error working with the wiki: Code[98]'. It is the velocity of the electron relative to these components that causes it to experience the Lorentz force.

Classical Theory
General Relativistics

Unipolar Induction

Relativistic Effect

Armature Reaction Theory

Torque

Back Torque

Experimental Results

Homopolar Generator Types

Patents

The United States Patent Office uses the clasification class 310 (Electrical generator or motor structure) and subclass 178 (Dynamoelectric Rotary D.C. Homopolar) for these devices. Many of the homopolar patents were obtained prior to 1975. Below is a list of homopolar generator patents.

American

G. D. Hathaway, "There was an error working with the wiki: Code[7], Direct current homopolar machine".

W. F. Weldon, "There was an error working with the wiki: Code[8] Homopolar machine ".

Antonios Challita, "There was an error working with the wiki: Code[9] Electrical machine".

W. F. Weldon, "There was an error working with the wiki: Code[10], Method of constructing a rotor assembly for homopolar generator".

W. F. Weldon, "There was an error working with the wiki: Code[11] Rotor assembly for homopolar generator".

W. F. Weldon, "There was an error working with the wiki: Code[12] Homopolar generator power supply system".

W. F. Weldon, "There was an error working with the wiki: Code[13] Removable brush mechanism for a homopolar generator ".

Esko Ensio hubta-Koivisto, "There was an error working with the wiki: Code[14] Electric unipolar motor".

E. C. Ketchum and D. H. Andrews, "There was an error working with the wiki: Code[15] Dynamo electric machine".

A. Kingsbury, "There was an error working with the wiki: Code[16] Dynamo electric machine".

W. A. Dick, "There was an error working with the wiki: Code[17] Dynamo electric machine".

There was an error working with the wiki: Code[99], "There was an error working with the wiki: Code[18] Dynamo electric machine".

H. Hertz, "There was an error working with the wiki: Code[19] Unipolar exciter for turbo-generators".

D. W. Troy, "There was an error working with the wiki: Code[20] Dynamo electric machine".

A. S. Hubbard, "There was an error working with the wiki: Code[21] Dynamo electric machine".

B. Von Ugrimoff, "There was an error working with the wiki: Code[22] Cooling device for electrical sliding contacts".

E. C. Ketchum, "There was an error working with the wiki: Code[23] Brush holders for dynamos".

J. E. Noeggerath, "There was an error working with the wiki: Code[24] Dynamo electric machine".

J. E. Noeggerath, "There was an error working with the wiki: Code[25] Dynamo electric machine".

J. E. Noeggerath, "There was an error working with the wiki: Code[26] Dynamo electric machine".

J. E. Noeggerath, "There was an error working with the wiki: Code[27] Dynamo electric machine".

J. E. Noeggerath, "There was an error working with the wiki: Code[28] Armature for unipolar machines".

J. E. Noeggerath, "There was an error working with the wiki: Code[29] Unipolar dynamo electric machine".

J. E. Noeggerath, "There was an error working with the wiki: Code[30] Acyclic machine".

J. E. Noeggerath, "There was an error working with the wiki: Code[31] Protective device for unipolar machine".

A. C. Eastwood, "There was an error working with the wiki: Code[32] System of control for electric motors".

J. E. Noeggerath, "There was an error working with the wiki: Code[33] Dynamo electric machine".

W. Mathiesen, "There was an error working with the wiki: Code[34] Unipolar dynamo".

There was an error working with the wiki: Code[100], "There was an error working with the wiki: Code[35] Unipolar generator".

J. E. Noeggerath, "There was an error working with the wiki: Code[36] Dynamo electric machine".

C. Macmillan, "There was an error working with the wiki: Code[37] Power transmission mechanism".

C. Macmillan, "There was an error working with the wiki: Code[38] Dynamo electric machine".

J. E. Noeggerath, "There was an error working with the wiki: Code[39] Unipolar alternating current machine".

E. C. Ketchum, "There was an error working with the wiki: Code[40] Dynamo".

H. H. Wait, "There was an error working with the wiki: Code[41] Dynamo electric machine".

J. E. Noeggerath, "There was an error working with the wiki: Code[42] Unipolar machine".

There was an error working with the wiki: Code[101], "There was an error working with the wiki: Code[43] Dynamo electric machine".

J. E. Noeggerath, "There was an error working with the wiki: Code[44] Electric motor".

E. R. Cox, Jr., "There was an error working with the wiki: Code[45] Dynamo electric machine or motor".

B. Bjarnason, "There was an error working with the wiki: Code[46] Dynamo electric machine".

F. W. Throop, "There was an error working with the wiki: Code[47] Dynamo electric machine".

G. Dalen and A Hultovist, "There was an error working with the wiki: Code[48] Dynamo electric machine".

F. G. Mayer, "There was an error working with the wiki: Code[49] Dynamo electric machine".

E. Thomson and M. J. Wightman, "There was an error working with the wiki: Code[50] Dynamo electric machine".

G. Rennerfelt, "There was an error working with the wiki: Code[51] Dynamo electric machine".

H. E. Dikeman, "There was an error working with the wiki: Code[52] Dynamo electric machine".

J. E. Maynadier, "There was an error working with the wiki: Code[53] Dynamo electric machine".

T. L. Willson, "There was an error working with the wiki: Code[54] Dynamo electric machine".

Nikola Tesla, "There was an error working with the wiki: Code[55] Dynamo electric machine".

J. B. Entz, "There was an error working with the wiki: Code[56] ''Dynamo electric machine".

There was an error working with the wiki: Code[102], "There was an error working with the wiki: Code[57] Unipolar dynamo electric machine".

There was an error working with the wiki: Code[103], "There was an error working with the wiki: Code[58] ''Dynamo electric machine".

R. Eickemeyer, "There was an error working with the wiki: Code[59] ''Electro magnetic and megneto electric machine".

R. Eickemeyer, "There was an error working with the wiki: Code[60] Device for taking electric currents from or to moving surfaces".

R. Eickemeyer, "There was an error working with the wiki: Code[61] Magneto electric and electro magnetic machine".

R. Eickemeyer, "There was an error working with the wiki: Code[62] Magneto electric and electro magnetic machine".

R. Eickemeyer, "There was an error working with the wiki: Code[63] Magneto electric and electro magnetic machine".

R. Eickemeyer, "There was an error working with the wiki: Code[64] Dynamo electric and electro magnetic machine".

R. Eickemeyer, "There was an error working with the wiki: Code[65] Dynamo electric and electro magnetic machine".

R. Eickemeyer, "There was an error working with the wiki: Code[66] Dynamo electric and electro magnetic machine".

R. Eickemeyer, "There was an error working with the wiki: Code[67] ''Magneto electric and electro magnetic machine".

There was an error working with the wiki: Code[104], "There was an error working with the wiki: Code[68] Unipolar dynamo electric machine".

There was an error working with the wiki: Code[105] and H. E. Walter"There was an error working with the wiki: Code[69] Dynamo electric machine".

C. Hering, "There was an error working with the wiki: Code[70] Unipolar dynamo electric machine".
Image:ForbesDynamo.png

There was an error working with the wiki: Code[106], "There was an error working with the wiki: Code[71] Dynamo electric machine".

A. E. G. Lubke, "There was an error working with the wiki: Code[72] Dynamo electric machine".

A. F. Delafield, "There was an error working with the wiki: Code[73] Dynamo electric machine".

C. E. Ball, "There was an error working with the wiki: Code[74] Dynamo or magneto-electric machine".

Related

There was an error working with the wiki: Code[124]

Bruce De Palma

There was an error working with the wiki: Code[125]

There was an error working with the wiki: Code[126]

There was an error working with the wiki: Code[127]

There was an error working with the wiki: Code[128]

There was an error working with the wiki: Code[129]

References

General references

Don Lancaster, "Shattering the homopolar myths". Tech Musings, October, 1997. (PDF)

Don Lancaster, "Understanding Faraday's Disk". Tech Musings, October, 1997. (PDF)

John David Jackson, Classical Electrodynamics, Wiley, 3rd ed. 1998, ISBN 0-471-30932-X

Olivier Darrigol, Electrodynamics from Ampere to Einstein, Oxford University Press, 2000, ISBN 0-19-850594-9

There was an error working with the wiki: Code[130], The Homopolar Handbook : A Definitive Guide to Faraday Disk and N-Machine Technologies. Washington, DC, U.S.A.: Integrity Research Institute, 2001. ISBN 0-9641070-1-5

Trevor Ophel and John Jenkin, (1996) Fire in the belly : the first 50 years of the pioneer school at the ANU Canberra : Research School of Physical Sciences and Engineering, Australian National University. ISBN 0-85800-048-2. (PDF)

Citations

There was an error working with the wiki: Code[75] Rudolf F. Graf, "Dictionary of Electronics Radio Shack, 1974-75". Fort Worth, Texas.

There was an error working with the wiki: Code[76] Ibid.

There was an error working with the wiki: Code[77] Thomas Valone, "Harnessing the Wheelwork of Nature : Tesla's Science of Energy", The Homopolar Generator: Tesla's Contribution. ISBN 1-931882-04-5 (ed. originally presented in the Proceedings of International Tesla Symposium, 1986, p. 6-29)

There was an error working with the wiki: Code[78] Ibid.

There was an error working with the wiki: Code[79] Nikola Tesla, "Notes on a Unipolar Dynamo". The Electrical Engineer, N.Y., Sept. 2, 1891. (Also available at tesla.hu, Article 18910902)

Further readings

Richard A. Marshall and William F. Weldon, "Parameter Selection for Homopolar Generators Used as Pulsed Energy Stores", Center for Electromechanics, University of Texas, Austin, Jul. 1980. (also published in: Electrical Machines and Electromechanics, 6:109-127, 1981.)

Oother articles

Robert Hebner, "Homopolar Generator". Homopolar Welding, UT-CEM.

"K2-64: Unipolar generator". physics.umd.edu.

Richard E. Berg and Carroll O. Alley, "The Unipolar Generator: A Demonstration of Special Relativity", Department of Physics, University of Maryland, 2005. (PDF)

Richard Fitzpatrick, "Magnetohydrodynamic theory ", The homopolar generator. farside.ph.utexas.edu, 2006-02-16.

"5K10.80 Homopolar Generator Lecture Demonstrations.". physics.brown.edu

There was an error working with the wiki: Code[131], "The Faraday Homopolar Generator Experiment". 13 April 1997.

William J. Beaty, "Untried Homopolar Generator Experiments". 1996.

Mike Galloway, "N-1 Homopolar Generator".

Bruce E. DePalma, "The Trombly-Kahn Homopolar Generator Critique of the N-Machine Constructed by Trombly & Kahn". 11 October 1985.

Bruce E. DePalma, "A review of:". 2 February 1995.

"The Faraday Disk Dynamo as the original over-unity device". Archer Energy Systems, Inc., 2006.

There was an error working with the wiki: Code[1], Wikipedia: The Free Encyclopedia. Wikimedia Foundation.

See also

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