HOMOPOLAR "FREE-ENERGY" GENERATOR TEST
Professor of Electrical Engineering (Emeritus)
Paper presented at the 1986 meeting
Society for Scientific Exploration
June 21, 1986
Revised February 1, 1987
HOMOPOLAR "FREE-ENERGY" GENERATOR TEST
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
This device, shown in Figs 1a and 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 
(and others ) 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
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.
Details of the generator construction are shown in Figs. 2 and 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 Fig. 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  in 1831 (Figs. 4,5) and shown
schematically in Fig. 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
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 , and their operating principles are described in a
number of texts .
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, (Fig 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
He concluded that a magnetic field is a property of space
itself, not attached to the magnet which serves to induce the
DePalma stated  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 .
Because the simple form shown in Fig. 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  (such as generators for developing large
currents for welding, ship degaussing, liquid metal
magnetohydrodynamic pumps for nuclear reactor cooling,
torquemotors for propulsion, etc.), some involving quite high
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
1. The magnetic field is concentrated near the axis where
the tangential velocity is low, reducing the generated
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 .
The generator was driven by a 3 phase a-c 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 Fig. 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
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 a-c circuit, particularly with
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 a-c ammeter that was used was of limited
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 .
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.
A schematic diagram of the test arrangement is shown in Fig. 9,
with the physical equipment shown in Fig. 10. 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 avaiable shunt-field d-c 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
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.
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 Fig. 11, in which it is seen that the output voltages are not
quite linearly related to magnet current, probably due to core
The more rapid departure of Vg from linearity may be due to
the different brush locations as seen on Fig 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 Fig. 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 Fig. 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 Fig. 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 Fig. 13, 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
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
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 .
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 Fig.
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 Fig. 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
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
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 Fig. 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 Fig. 17
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.
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.
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
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 a-c ripple superimposed on the measured d-c, 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
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
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
occured to a number of people and several such machines have
At least one of these known to me , using what seemed to
be a good design techniques, was unsuccessful.
1. DePalma, 1979a,b,c, 1981, 1983, 1984, etc.
2. For example, Satelite 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,
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,
7. DePalma, op. cit.
. 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.
[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
[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
[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
[Das Gupta, 1961] - A. K. Das Gupta, "Design of self-compensated
high current comparatively higher voltage homopolar generators",
AIEE Trans. Oct 1961, p567-73. (Discusses very high current
homopolar generator design)
[Das Gupta, 1962] - A. K. Das Gupta, "Commutatorless D-C generators
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 Mar 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. v.28, Dec 1928, p.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)
[Lamme, 1912] - B. G. Lamme, "Development of a successful direct-
current 2000-kW unipolar generator", AIEE Trans. 28 June 1912,
p1811-40. (Early discussion of design of high power homopolar
[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
[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
[Savage, 1949] - Norton Savage, letter re [Cohn, 1949a]; ELECTRICAL
ENGINEERING, July 1949, p645. (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, p.544-59. (Theory and experiment on torque in a
(Sysop note: The following figure also had an accompanying drawing)
Figure 5 - Transcription of the first experiment showing generation
of electrical power in a moving conductor by Michael
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
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
(Sysop note: a sketch appeared in this area)
(Sysop note: The following figure also had an accompanying drawing)
Figure 7 - Test of a rotating magnet by Michael Faraday, December
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
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
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
(Sysop note: The following figure also had an accompanying drawing)
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-phms
Reduction of the above data gives as the equivalent circuit for the
(Sysop note: a drawing R(internal) = 62.5 micro-ohms
appeared in this area) R(brush) = 114.25 " "
R(shunt) = 31.25 " "
17 DECEMBER 1980
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
MOTOR ARMATURE POWER 4782 5226 6028
INCREMENT 444 802
METER BRUSH VOLTAGE .005 1.231 1.070
OUTPUT CURRENT 0 0 4776
GENERATED VOLTAGE 1.280 (1.280)
GENERATED POWER 0 0 (6113)
HOMOPOLAR GENERATOR TEST - BIG SPRINGS RANCH APRIL 26, 1986
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