Robert KINCHELOE
N-Machine Test
HOMOPOLAR "FREE-ENERGY" GENERATOR TEST
by Robert
Kincheloe
Professor of Electrical
Engineering (Emeritus), Stanford University
Paper presented at the
1986 meeting of the Society for Scientific Exploration (San
Francisco, June 21, 1986)
Revised February 1, 1987
Abstract
Known for over 150 years, the Faraday homopolar generator has been claimed to provide a basis for so-called "free-energy" generation, in that under certain conditions the extraction of electrical output energy is not reflected as a corresponding mechanical load to the driving source.
During 1985, I was invited to test such a machine. While it did not perform as claimed, repeatable data showed anomalous results that did not seem to conform to traditional theory.
In particular, under certain assumptions about internally generated output voltage, the increase in input power when power was extracted from the generator over that measured due to frictional losses with the generator unexcited seemed to be either about 13% or 20% of the maximum computed generated power, depending on interpretation.
The paper briefly reviews the homopolar generator, describes the tests on this particular machine, summarizes and presents tentative conclusions from the resulting data.
The Sunburst Homopolar Generator
In July, 1985, I became aware of and was invited to examine and test a so-called free-energy generator known as the Sunburst N Machine.
This device, shown in Figures 1a & 1b, was proposed by Bruce DePalma and constructed by Charya Bernard of the Sunburst Community in Santa Barbara, CA, about 1979.
The term "free-energy" refers to the claim by DePalma [1] (and others [2]) that it was capable of producing electrical output power that was not reflected as a mechanical load to the driving mechanism but derived from presumed latent spatial energy.
Apart from mechanical frictional and electrical losses inherent in the particular construction, the technique employed was claimed to provide a basis for constructing a generator which could supply the energy to provide not only its own motive power but also additional energy for external use. From August 1985 to April 1986 I made a series of measurements on this particular machine to test these claims.
Generator Description
Details of the generator construction are shown in Figure 2 and Figure 3.
It consists essentially of an electromagnet formed by a coil of 3605 turns of #10 copper wire around a soft iron core which can be rotated with the magnetic field parallel to and symmetrical around the axis of rotation.
At each end of the magnet are conducting bronze cylindrical plates, on one of which are arranged (as shown in Figure 3) one set of graphite brushes for extracting output current between the shaft and the outer circumference and a second set of metering brushes for independently measuring the induced voltage between these locations.
A third pair of brushes and slip rings supply the current for the electromagnet. A thick sheath of epoxy-impregnated fiberglass windings allow the magnet to be rotated at high speed.
The generator may be recognized as a so-called homopolar, or acyclic machine, a device first investigated and described by Michael Faraday [3] in 1831 (Figure 4 & Figure 5) and shown schematically in Figure 6.
It consists of a cylindrical conducting disk immersed in an axial magnetic field, and can be operated as a generator with sliding brushes extracting current from the voltage induced between the inner and outer regions of the disk when the rotational energy is supplied by an external driving source.
The magnitude of the incremental radial generated voltage is proportional to both the strength of the magnetic field and the tangential velocity, so that in a uniform magnetic field the total voltage is proportional to the product of speed times the difference between the squares of the inner and outer brush radii.
The device may also be used as a motor when an external voltage produces an radial current between the sliding brushes.
There have been a number of commercial applications of homopolar motors and generators, particularly early in this century [4], and their operating principles are described in a number of texts [5].
The usual technique is to use a stationary magnet to produce the magnetic field in which the conducting disk (or cylinder) is rotated.
Faraday found, however, (Figure 7) that it does not matter whether the magnet itself is stationary or rotating with the disk as long as the conductor is moving in the field, but that rotating the magnet with the conducting disk stationary did not produce an induced voltage.
He concluded that a magnetic field is a property of space itself, not attached to the magnet which serves to induce the field [6].
DePalma stated [7] that when the conducting disk is attached to a rotating magnet, the interaction of the primary magnetic field with that produced by the radial output current results in torque between the disk and the magnet structure which is not reflected back to the mechanical driving source.
Lenz's law therefore does not apply, and the extraction of output energy does not require additional driving power. This is the claimed basis for extracting "free" energy.
Discussions of the torque experienced by a rotating magnet are also discussed in the literature [8].
Because the simple form shown in Figure 6 has essentially one conducting path, such a homopolar device is characterized by low voltage and high current requiring a large magnetic field for useful operation.
Various homopolar devices have been used for specialized applications [9] (such as generators for developing large currents for welding, ship degaussing, liquid metal magnetohydrodynamic pumps for nuclear reactor cooling, torque motors for propulsion, etc.), some involving quite high power.
These have been extensively discussed in the literature, dealing with such problems as developing the high magnetic fields required (sometimes using superconducting magnets in air to avoid iron saturation effects), the development of brushes that can handle the very high currents and have low voltage drop because of the low output voltage generated, and with counteracting armature reaction which otherwise would reduce the output voltage because of the magnetic field distortion resulting from the high currents.
From the standpoint of prior art, the design of the Sunburst generator is inefficient and not suitable for power generation:
1. The magnetic field is concentrated near the axis where the tangential velocity is low, reducing the generated voltage.
2. Approximately 4 kilowatts of power are required to energize the magnet, developing enough heat so that the device can only be operated for limited periods of time.
3. The graphite brushes used have a voltage drop almost equal to the total induced voltage, so that almost all of the generated power is consumed in heating the brushes.
4. The large contacting area (over 30 square inches) of the brushes needed for the high output current creates considerable friction loss.
Since this machine was not intended as a practical generator but as a means for testing the free energy principle, however, from this point of view efficiency in producing external power was not required or relevant.
DePalma's Results with the Sunburst Homopolar Generator
In 1980 DePalma conducted tests with the Sunburst generator, describing his measurement technique and results in an unpublished report [10].
The generator was driven by a 3 phase AC 40 horsepower motor by a belt coupling sufficiently long that magnetic fields of the motor and generator would not interact. A table from this report giving his data and results is shown in Figure 8.
For a rotational speed of 6000 rpm an output power of 7560 watts was claimed to require an increase of 268 watts of drive power over that required to supply losses due to friction, windage, etc., as measured with the output switch open.
If valid, this would mean that the output power was 28.2 times the incremental input power needed to produce it. Several assumptions were made in this analysis:
1. The drive motor input power was assumed to be the product of the line voltage and current times the appropriate factor for a three-phase machine and an assumed constant 70% power factor.
There was apparently no consideration of phase angle change as the motor load increased. This gives optimistic results, since consideration of phase angle is necessary for calculating power in an AC circuit, particularly with induction motors.
It might also be noted that the measured incremental line current increase of 0.5 ampere (3.3%) as obtained with the analog clamp-on AC ammeter that was used was of limited accuracy.
2. The output power of the generator was taken to be the product of the measured output current and the internally generated voltage in the disk less the voltage drop due only to internal disk resistance. Armature reaction was thus neglected or assumed not to be significant.
3. The generated voltage which produced the current in the main output brushes was assumed to be the same as that measured at the metering brushes, and the decrease in metered voltage from 1.5 to 1.05 volts when the output switch is closed was assumed to be due to the internal voltage drop resulting from the output current flowing through the internal disk resistance that is common to both sets of brushes and calculated to 62.5 microohms.
Of these, the first assumption seems the most serious, and it is my opinion that the results of this particular test were inaccurate.
Tim Wilhelm of Stelle, Illinois, who witnessed tests of the Sunburst generator in 1981, had a similar opinion [11].
Recent Tests of the Sunburst Generator
Being intrigued by DePalma's hypothesis, I accepted the offer by Mr. Norman Paulsen, founder of the Sunburst Community, to conduct tests on the generator which apparently had not been used since the tests by DePalma and Bernard in 1979.
Experimental Setup
A schematic diagram of the test arrangement is shown in Figure 9, with the physical equipment shown in Figure 10a. The generator is shown coupled by a long belt to the drive motor behind it, together with the power supplies and metering both contained within and external to the Sunburst power and metering cabinet.
Figure 10b shows the panel of the test cabinet which provided power for the generator magnet and motor field. The 4-1/2 digit meters on the panel were not functional and were not used; external meters were supplied.
I decided to use an available shunt-field DC drive motor to facilitate load tests at different speeds and to simplify accurate motor input power measurements.
Referring to Figure 9, variacs and full-wave bridge rectifiers provided variable d-c supplies for the motor armature and field and the homopolar generator magnet.
Voltages and currents were measured with Micronta model 11-191 3-1/2 digit meters calibrated to better than 0.1% against a Hewlett Packard 740B Voltage Standard that by itself was accurate to better than .005%.
Standard meter shunts together with the digital voltmeters were used to measure the various currents. With this arrangement the generator speed could be varied smoothly from 0 to over 7000 rpm, with accurate measurement of motor input power, metered generator output voltage Vg and generator output current Ig.
Speed was measured with a General Radio model 1531 Strobotac which had a calibration accuracy of better than 2% (as verified with a frequency counter) and which allowed determination of relative speed changes of a few rpm of less.
Small changes in either load or input power were clearly evident because of the sensitivity of the Strobotac speed measurement, allowing the motor input power to be adjusted with the armature voltage variac to obtain the desired constant speed with no acceleration or deceleration before taking readings from the various meters.
Generator Tests
Various tests were conducted with the output switch open to confirm that generated voltage at both the output brushes (Vbr) and metering brushes (Vg) were proportional to speed and magnetic field, with the polarity reversing when magnetic field or direction of rotation were reversed.
Tracking of Vbr and Vg with variation of magnetic field is shown in Figure 11, in which it is seen that the output voltages are not quite linearly related to magnet current, probably due to core saturation.
The more rapid departure of Vg from linearity may be due to the different brush locations as seen on Figure 3, differences in the magnetic field at the different brush locations, or other causes not evident. An expanded plot of this voltage difference is shown in Figure 12, and is seen to considerably exceed meter error tolerances.
Figure 11 also shows an approximate 300 watt increase in drive motor armature power as the magnet field was increased from 0 to 19 amperes.
(The scatter of input power measurements shown in the upper curve of Figure 11 resulted from the great sensitivity of the motor armature current to small fluctuations in power line voltage, since the large rotary inertia of the 400 pound generator did not allow speed to rapidly follow line voltage changes).
At first it was thought that this power loss might be due to the fact that the outer output brushes were arranged in a rectangular array as shown in Figure 3.
Since they were connected in parallel but not equidistant from the axis the different generated voltages would presumably result in circulating currents and additional power dissipation.
Measurement of the generated voltage as a function of radial distance from the axis as shown in Figure13, however, showed that almost all of the voltage differential occurred between 5 and 12 cm, presumably because this was the region of greatest magnetic field due to the centralized iron core.
The voltage in the region of the outer brushes was almost constant, with a measured variation of only 3.7% between the extremes, so that this did not seem to explain the increase in input power. The other likely explanation seems to be that there are internal losses in the core and other parts of the metal structure due to eddy currents, since these are also moving conductors in the field.
In any event, the increase in drive power was only about 10% for the maximum magnet current of 19 amperes.
Figure 14 typifies a number of measurements of input power and generator performance as a function of speed and various generator conditions.
Since the generator output knife switch procedure was very stiff and difficult to operate the procedure used was to make a complete speed run from zero to the maximum speed and descending again to zero with the switch open, taking readings at each speed increment with the magnet power both off and on.
The procedure was then repeated with the switch closed. (It was noted that during the descending speed run the input power was a few percent lower than for the same speed during the earlier ascending speed run; this was presumably due to reduced friction as the brushes and/or bearings became heated. In plotting the data the losses for both runs were averaged which gave a conservative result since the losses shown in the figures exceed the minimum values measured).
The upper curve (a) shows the motor armature input power with a constant motor field current of 6 amperes as the speed is varied with no generator magnet excitation and is seen to reach a maximum of 4782 watts as the speed is increased to 6500 rpm.
This presumably represents the power required to overcome friction and windage losses in the motor, generator, and drive belt, and are assumed to remain essentially constant whether the generator is producing power or not [12].
Curve 14b shows the increase of motor armature power over that of curve (a) that results from energizing the generator magnet with a current of 16 amperes but with the generator output switch open so that there is no output current (and hence no output power dissippation).
This component of power (which is related to the increase of drive motor power with increased magnet current as shown in Figure 11 as discussed above) might also be present whether or not the generator is producing output current and power, although this is not so evident since the output current may affect the magnetic field distribution.
Curve 14c shows the further increase of motor armature input power over that of curves (a) plus (b) that results when the output switch is closed, the generator magnet is energized and output current is produced.
It is certainly not zero or negligible but rises to a maximum of 802 watts at 6500 rpm. The total motor armature input power under these conditions is thus the sum of (a), (b), and (c) and reaches a maximum of 6028 watts at 6500 rpm.
The big question has to do with the generated output power. The measured output current at 6500 rpm was 4776 amperes; the voltage at the metering brushes was 1.07 volts.
Using a correction factor derived from Figure 12 and assuming a common internal voltage drop due to a calculated disk resistance of 38 microohms, a computed internal generated potential of 1.28 volts is obtained which if multiplied by the measured output current indicates a generated power of 6113 watts.
All of this power is presumably dissipated in the internal and external circuit resistances, the brush loss due both to the brush resistance and the voltage drops at the contact surfaces between the brushes and the disk (essentially an arc discharge), and the power dissipated in the 31.25 microohm meter shunt.
It still represents power generated by the machine, however, and exceeds the 802 watts of increased motor drive power due solely to closing the generator output switch and causing output current to flow by a factor of 7.6 to 1.
If the 444 watts of increased input power that resulted from energizing the magnet with the output switch open is assumed to have been converted to generated output power and hence should be included as part of the total increased drive motor power required to produce generated output, the computed 6113 watts of generated power still exceeds the total input power of 444 watts plus 802 watts by a factor of 4.9 to 1.
The computed output power even slightly exceeds the total motor armature input power including all frictional and windage losses of 6028 watts under these conditions (although the total system effeciency is still less than 100% because of the generator magnet power of approximately 2300 watts and motor field power of about 144 watts which must be added to the motor armature power to obtain total system input power).
It would thus seem that if the above assumptions are valid that DePalma correctly predicted that much of the generated power with this kind of machine is not reflected back to the motive source.
Figure 15 summarizes the data discussed above.
To further examine the question of the equivalence between the internally generated voltage at the main output brushes and that measured at the metering brushes, a test was made of the metered voltage as a function of speed with the generator magnet energized with a current of 20 amperes both with the output switch open and closed. The resulting data is shown in Figure 16.
The voltage rises to about 1.32 volts at 6000 rpm with the switch open (which is close to that obtained by DePalma) and drops 0.14 volts when the switch is closed and the measured output current is 3755 amperes, corresponding to an effective internal resistance of 37 microohms.
Even if this were due to other causes, such as armature reaction, it does not seem likely that there would be a large potential drop between the output and metering brushes because of the small distance, low magnetic field (and radial differential voltage), and large mass of conducting disk material.
Internal currents many times the measured output current of almost 4000 amperes would be required for the voltage difference between the outer metering and output brushes to be significant and invalidate the conclusions reached above.
A further method of testing the validity of the assumed generated output potential involved an examination of the voltage drop across the graphite brushes themselves.
Many texts on electrical machinery discuss the brush drop in machines with commutators or slip rings. All of those examined agree that graphite brushes typically have a voltage drop that is essentially constant at approximately one volt per brush contact when the current density rises above 10-15 amperes per square centimeter.
To compare this with the Sunburst machine the total brush voltage was calculated by subtracting the IR drop due to the output current in the known (meter shunt) and calculated (disk, shaft, and brush lead) resistances from the assumed internally generated output voltage. The result in Figure17 shows that the brush drop obtained in this way is even less than that usually assumed, as typified by the superimposed curve taken from one text.
It thus seems probable that the generated voltage is not significantly less than that obtained from the metering brushes, and hence the appropriateness of the computed output power is supported.
Conclusions
We are therefore faced with the apparent result that the output power obtained when the generator magnet is energized greatly exceeds the increase in drive power over that needed to supply losses with the magnet not energized. This is certainly anomalous in terms of convential theory. Possible explanations?
1. There could be a large error in the measurements resulting from some factor such as noise which caused the digital meters to read incorrectly or grossly inaccurate current shunt resistances.
If the measured results had shown that the computed generated output power exceeded the input drive power by only a few percent this explanation would be reasonable and would suggest that more careful calibration and measurements might show that the results described above were due to measurement error.
With the data showing such a large ratio of generated power to input power increase, however, in my opinion this explanation of the results seems unlikely.
(A later test showed that the digital meters are insensitive to a large AC ripple superimposed on the measured DC, but within their rated accuracy of 0.1% give a true average value).
2. There could be a large difference between the measured voltage at the metering brushes and the actual generated voltage in the output brush circuit due to armature reaction, differences in the external metering and output circuit geometry, or other unexplained causes.
As discussed above the various data do not seem to support this possibility.
3. DePalma may have been right in that there is indeed a situation here whereby energy is being obtained from a previously unknown and unexplained source.
This is a conclusion that most scientists and engineers would reject out of hand as being a violation of accepted laws of physics, and if true has incredible implications.
4. Perhaps other possibilities will occur to the reader.
The data obtained so far seems to have shown that while DePalma's numbers were high, his basic premise has not been disproved. While the Sunburst generator does not produce useful output power because of the internal losses inherent in the design, a number of techniques could be used to reduce the friction losses, increase the total generated voltage and the fraction of generated power delivered to an external load.
DePalma's claim of free energy generation could perhaps then be examined.
I should mention, however, that the obvious application of using the output of a "free-energy" generator to provide its own motive power, and thus truly produce a source of free energy, has occurred to a number of people and several such machines have been built.
At least one of these known to me [13], using what seemed to be a good design techniques, was unsuccessful.
Footnotes
1. DePalma, 1979a,b,c, 1981,
1983, 1984, etc.
2. For example, Satellite
News, 1981, Marinov, 1984, etc.
3. Martin, 1932, vol. 1,
p.381.
4. Das Gupta, 1961, 1962;
Lamme, 1912, etc.
5. See, for example, Bumby,
1983; Bewley, 1952; Kosow, 1964; Nasar,1970.
6. There has been much
discussion on this point in the literature, and about
interpretation of flux lines. Bewley, 1949; Cohn,
1949a,b; Crooks, 1978; Cullwick, 1957; Savage, 1949.
7. DePalma, op. cit.
8. Kimball, 1926; Zeleny,
1924.
9. Bumby, Das Gupta, op. cit.
10. DePalma, 1980.
11. Wilhelm, 1980, and
personal communication.
12. The increase
in motor losses with increased load are neglected in
this discussion because of a lack of accurate values for
armature and brush resistances, magnetic field distortion
resulting from armature reaction, etc. Such losses, while
small, would be appreciable, however; their inclusion
would further increase the ratio of generated to drive power
so that the results described are conservative.
13. Wilhelm, 1981, and
personal communication.
References
[Bewley, 1949] - L. V. Bewley: letter re: [Cohn, 1949a]; ELECTRICAL ENGINEERING, Dec. 1949, p.1113-4. (Claims error in Cohn's paper)
[Bewley, 1952] - L. V. Bewley: FLUX LINKAGES & ELECTROMAGNETIC INDUCTION, Macmillan, NY, 1952. (Explanation of induction phenomena and the Faraday generator)
[Bumby, 1983] - J. R. Bumby: SUPERCONDUCTING ROTATING ELECTRICAL MACHINES, Claredon Press, 1983. (Homopolar designs, high current brushes including liquid metal)
[Cohn, 1949a] - George I. Cohn: "Electromagnetic Induction", ELECTRICAL ENGINEERING, May 1949, p441-7. (Unipolar generator as paradox)
[Cohn, 1949b] - George Cohn: letter re: [Savage, 1949]; ELECTRICAL ENGINEERING, Nov 1949, p1018. (Responds to criticism by Savage)
[Crooks, 1978] - M. J. Crooks, et al.: "One-piece Faraday generator: A paradoxical experiment from 1851", Am. J. Phys. 46(7), July 1978, p729-31. (Derives Faraday generator performance using Maxwell's equations)
[Cullwick, 1957] - E. G. Cullwick: ELECTROMAGNETISM AND RELATIVITY, Longmans & Green, London, 1957. (Chapter 10, "A Rotating Conducting Magnet", pp.141-60, discusses question of flux rotation with magnet)
[Das Gupta, 1961] - A. K. Das Gupta: "Design of self-compensated high current comparatively higher voltage homopolar generators", AIEE Trans., Oct 1961, pp. 567-73. (Discusses very high current homopolar generator design)
[Das Gupta, 1962] - A. K. Das Gupta: "Commutatorless D-C generator capable to supply currents more than one million amperes, etc"; AIEE Trans. Oct 1962, p399-402. (Discusses very high current low voltage Faraday generators)
[DePalma, 1979a] - Bruce DePalma: "EXTRACTION OF ELECTRICAL ENERGY DIRECTLY FROM SPACE: THE N-NACHINE", Simularity Institute, Santa Barbara CA, 6 March 1979. (Discusses homopolar generator or N-Machine as free-energy source)
[DePalma, 1979b] - Bruce DePalma: "The N-Machine", Paper given at the World Symposium on Humanity, Pasadena, CA, 12 April 1979. (Describes background, development of "free-energy" theories)
[DePalma, 1979c] - Bruce DePalma: "ROTATION OF A MAGNETIZED GYROSCOPE", Simularity Institute Report #33, 16 July 1979. (Describes design of Sunburst homopolar generator)
[DePalma, 1980] - Bruce DePalma: "Performance of the Sunburst N-Machine", Simularity Institute, Santa Barbara, CA, 17 December 1980. (Description of tests and results)
[DePalma, 1981] - Bruce DePalma: "Studies on rotation leading to the N-Machine", DePalma Institute, 1981 (Transcript of talk; discusses experiments with gravity that led to development of idea of free-energy machine)
[DePalma, 1983] - Bruce DePalma: "THE ROTATION OF THE UNIVERSE", DePalma Institute Report #83, Santa Barbara, CA, 25 July 1983. (Uses Faraday disc to discuss universal principles).
[DePalma, 1984] - Bruce DePalma: "THE SECRET OF THE FARADAY DISC", DePalma Institute, Santa Barbara, CA, 2 Feb 1984. (Claims explanation of Faraday disc as a free-energy device)
[Kimball, 1926] - A. L. Kimball, Jr.: "Torque on revolving cylindrical magnet", PHYS. REV. 28, Dec. 1928, pp.1302-8. (Alternative analysis of torque in a homopolar device to that of Zeleny and Page, 1924)
[Kosow, 1964] - Irving L. Kosow: ELECTRICAL MACHINERY & CONTROL, Prentice-Hall, 1964. (Discusses high current homopolar [acyclic] generators)
[Lamme, 1912] - B. G. Lamme: "Development of a successful direct-current 2000-kW unipolar generator", AIEE Trans. 28 June 1912, pp.1811-40. (Early discussion of design of high power homopolar generator)
[Marinov, 1984]- Stefan Marinov: THE THORNY WAY OF TRUTH, Part II; Graz, Austria, 1984 (Advertisement in NATURE). (Claims free-energy generator proved by DePalma, Newman)
[Martin, 1932] - Thomas Martin (ed): FARADAY'S DIARY, Bell, 1932, in 5 vols. (Transcription and publication of Faraday's original diaries)
[Nasar, 1970] - S. Nasar: ELECTROMAGNETIC ENERGY CONVERSION DEVICES & SYSTEMS, Prentice-Hall, 1970. (Discusses principles and applications of acyclic [homopolar] machines)
[Satellite News, 1981] - "Researchers see long-life satellite power systems in 19th century experiment", Research News, SATELLITE NEWS, 15 June 1981. (Reports DePalma's claim for free-energy generator)
[Savage, 1949] - Norton Savage: letter re: [Cohn, 1949a]; ELECTRICAL ENGINEERING, July 1949, p. 645. (Claims error in Cohn's paper)
[Wilhelm, 1980] - Timothy J. Wilhelm: "INVESTIGATIONS OF THE N-EFFECT ONE-PIECE HOMOPOLAR DYNAMOS, ETC. (Phase I)", Stelle, IL, 12 Sept. 1980. (Discusses tests on DePalma's N-Machine)
[Wilhelm, 1981] - Timothy J. Wilhelm: "INVESTIGATIONS OF THE N-EFFECT ONE-PIECE HOMOPOLAR DYNAMOS, ETC. (Phase II)", Stelle, IL, 10 June 1981. (Design and tests of improved homopolar generator/motor)
[Zeleny, 1924] - John Zeleny & Leigh Page: "Torque on a cylindrical magnet through which a current is passing", PHYS. REV. v.24, 14 July 1924, pp.544-59. (Theory and experiment on torque in a homopolar device)
Figure 1a & 1 b ~ Not shown (poor quality image)
Figure 2 ~ Sunburst Homopolar Generator (side view):
Figure 3 ~ Sunburst Homopolar Generator; output (brush) end view:
Figure 4 / Figure 5 ~ Transcription of Faraday's first experiment showing generation of electrical power in a moving conductor (Faraday's Diary, 28 October 1831):
99. Made many expts. with a copper revolving plate, about 12 inches in diameter and about 1/5 of inch thick, mounted on a brass axle.
To concentrate the polar action two small magnets 6 or 7 inches long, about 1 inch wide and half an inch thick were put against the front of the large poles, transverse to them and with their flat sides against them, and the ends pushed forward until sufficiently near; the bars were prevented from slipping down by jars and shakes by means of string tied round them.
100. The edge of the plate was inserted more of less between the two concentrated poles thus formed. It was also well amalgamated, and then contact was made with this edge in different places by conductors formed from equally thick copper plate and with the extreme end edges grooved and amalgamated so as to fit on to and have contact with the edges of the plate. Two of these were attached to a piece of card board by thread at such *[99]
Figure 6 ~ Homopolar (Acyclic) Generator:
Figure 7 - Test of a rotating magnet by Michael Faraday (December 26, 1831):
255. A copper disc was cemented on the top of a cylinder magnet, paper intervening, the top being the marked pole; the magnet supported so as to rotate by means of string, and the wires of the galvanometer connected with the edge and the axis of the copper plate. When the magnet and disc together rotated unscrew the marked end of the needle went west. When the magnet and disc rotated screw the marked end of the needle went east.
256. This direction is the same as that which would have resulted if the copper had moved and the magnet been still. Hence moving the magnet causes no difference provided the copper moves. A rotating and a stationary magnet cause the same effect.
257. The disc was then loosed from the magnet and held still whilst the magnet itself was revolved; but now no effect upon the galvanometer. Hence it appears that, of the metal circuit in which the current is to be formed, different parts must move with different angular velocities. If with the same, no current is produced, i.e. when both parts are external to the magnet.
Figure 8 ~ Test data from report by Bruce DePalma:
PERFORMANCE OF THE SUNBURST HOMOPOLAR GENERATOR
Machine
speed:
6000
r.p.m.
drive motor
current no
load
15
amperes
drive motor
current increase
when N machine
is
loaded
1/2
ampere max.
Voltage output of N
generator no
load
1.5 volts d.c.
Voltage output of N generator
loaded
1.05
v.d.c.
Current output of N
generator
7200
amperes
(225
m.v. across shunt @ 50 m.v./1600 amp.)
Power output of
N-Machine
7560
watts = 10.03 H.p.
Incremental power ratio
=
7560/268
28.2
watts out/watts in
Internal resistance of
generator
62.5
micro-ohms
Reduction of the above data gives as the equivalent circuit for the machine:
R(internal) = 62.5
micro-ohms
R(brush) =
114.25 " "
R(shunt)
= 31.25 " "
Figure 9 ~ Schematic diagram of generator test arrangement:
Figure 10a & 10b ~ Sunburst power unit & test panel (Not shown: poor image quality)
Figure 11 ~ Input power & generated voltage vs. magnet current:
Figure 12 ~ metering & output brush voltage difference vs. magnet current:
Figure 13 ~ Radial voltage distribution:
Figure 14 ~ Input & output power vs. speed:
Figure 15 - Summary of test results at 6500 rpm:
I II III
MAGNET
POWER
OFF
ON
ON
OUTPUT
SWITCH
OPEN
OPEN CLOSED
SPEED
6500
6500
6500 RPM
MAGNET
CURRENT
0
16
16
AMPERES
MOTOR ARMATURE
POWER
4782
5226
6028
WATTS
INCREMENT
444
802
WATTS
METER BRUSH
VOLTAGE
.005
1.231
1.070 VOLTS
OUTPUT
CURRENT
0
0
4776
AMPERES
GENERATED
VOLTAGE
1.280
(1.280) VOLTS
GENERATED
POWER
0
0
(6113)
WATTS
HOMOPOLAR GENERATOR TEST - BIG SPRINGS RANCH APRIL 26, 1986
Figure 16 ~ Metering brush voltage vs. speed:
Figure 17 ~ Calcualted output brush voltage drop vs. current:
