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Author Topic: Homopolar Generators (N-Machine) by Bruce de Palma  (Read 244903 times)

Offline PulsedPower

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Re: Homopolar Generators (N-Machine) by Bruce de Palma
« Reply #45 on: February 21, 2008, 08:05:27 AM »
Quote
If you attach the magnets to the shaft so they spin WITH the disk,
there IS NO BACK EMF.

theres nothing to push against, the magnetic source is spinning with the disk.

but the field, being circular, remains stationary


In my previous post I mentioned that there is no torque reaction on the magnets anyway in fact quite a few homopolar machines put the rotor inside a large air core solenoid. Because the magnetic field produced by rotor current flow is orthogonal to the magnet field there can be no torque reaction on the magnet. This is the case with a uniform field, if the field is not uniform in the direction of motion then there is a some induction in the rotor producing a field and consequently some torque reaction on the magnet assembly, If the magnets travel with the rotor then there will be no eddy currents induced in the rotor  as even a nonuniform field will be unchanging with respect to the rotor. But as the magnets are not moving with respect to the return current path eddy currents can be induced in it instead. Non uniformity of the field in the radial direction produces no eddy currents. It is difficult to describe without drawing it. AFAIK as the previous poster mentioned having the magnets travel with the field will still produce voltage when measured from a stationary point most likely because the magnetic field is now moving with respect to the return conductor.

I am guessing that this lack of torque reaction with the field magnet is what you mean by nothing to push against, but the return current path provides plenty to push against the current in it sets up a magnetic field opposite to the current flowing though the rotor. That 27000 rpm 140 lb rotor mentioned in my other post didn't come to a stop by itself. I understand that there might be some difficulties measuring the power input to a homopolar generator if it is measured by running it on cradles like a brake dynanometer as some torque will appear outside the machine if care is not taken in locating the output terminals maybe this is why some people asociate them with over unity power output. Also the strong stray magnetic fields associated with them may also play havoc with the instruments used to measure the power input and output. In a pulsed power application the input power is well defined as the polar moment of inertia and the rpm of the rotor are easily quantified and the output power is measured with instruments which are designed to deal with the strong sources of interference associated with this environment

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Offline argona369

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Re: Homopolar Generators (N-Machine) by Bruce de Palma
« Reply #46 on: February 22, 2008, 04:58:41 AM »
Quote
If you attach the magnets to the shaft so they spin WITH the disk,
there IS NO BACK EMF.

theres nothing to push against, the magnetic source is spinning with the disk.

but the field, being circular, remains stationary


In my previous post I mentioned that there is no torque reaction on the magnets anyway in fact quite a few homopolar machines put the rotor inside a large air core solenoid. Because the magnetic field produced by rotor current flow is orthogonal to the magnet field there can be no torque reaction on the magnet. This is the case with a uniform field, if the field is not uniform in the direction of motion then there is a some induction in the rotor producing a field and consequently some torque reaction on the magnet assembly, If the magnets travel with the rotor then there will be no eddy currents induced in the rotor  as even a nonuniform field will be unchanging with respect to the rotor. But as the magnets are not moving with respect to the return current path eddy currents can be induced in it instead. Non uniformity of the field in the radial direction produces no eddy currents. It is difficult to describe without drawing it. AFAIK as the previous poster mentioned having the magnets travel with the field will still produce voltage when measured from a stationary point most likely because the magnetic field is now moving with respect to the return conductor.

I am guessing that this lack of torque reaction with the field magnet is what you mean by nothing to push against, but the return current path provides plenty to push against the current in it sets up a magnetic field opposite to the current flowing though the rotor. That 27000 rpm 140 lb rotor mentioned in my other post didn't come to a stop by itself. I understand that there might be some difficulties measuring the power input to a homopolar generator if it is measured by running it on cradles like a brake dynanometer as some torque will appear outside the machine if care is not taken in locating the output terminals maybe this is why some people asociate them with over unity power output. Also the strong stray magnetic fields associated with them may also play havoc with the instruments used to measure the power input and output. In a pulsed power application the input power is well defined as the polar moment of inertia and the rpm of the rotor are easily quantified and the output power is measured with instruments which are designed to deal with the strong sources of interference associated with this environment


Hi Pulse,
It sounds like you know your homopolar generators.
I never thought of the lack of torque back into the magnetic source.
But just the closing path producing torque relative to
The rotor. that is interesting.

I?ve always wondered if there was a way to do away
with any slip rings. A ?one piece? device that would rotate as a whole
(Closing path included) driving a load.
 But I think it would be fundamentally impossible.
But maybe there would be a way?

Btw , the spiral disk I believe was not for a higher voltage
But to counteract torque and reinforce the magnet?

"Because the current is flowing in a large circle at the rim of the disk, the magnetic field created
by the current not only does not work against the field magnet above the circular plate, as in
conventional generators, but it actually reinforces the magnet"

>Tesla's Fuelless Generator,
>http://home.comcast.net/~onichelson/Fuelless.pdf
>from this page which has some good articles,
>http://tesla.nichelson.googlepages.com/home

Offline sm0ky2

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Re: Homopolar Generators (N-Machine) by Bruce de Palma
« Reply #47 on: February 22, 2008, 05:03:52 AM »
our set-up in the lab was a 15-inch copper dsk

mounted between two disk-magnets.

S/N facing together on either side of the disk. Steady power from a power-supply to run a DC motor, which turned the device. The power produced was nothing near overunity, since our motor was grossly overpowered for the mass of our homopolar generator.

What i remember distinctly, was the fact that there was no difference in torque when current was being drawn off the disk - between a carbon-brush on the exterior rim and a slip-ring on the shaft. 

I dont know what the set-up was on that massive disk that "came to a stop", but when we replicated the generator, using a rotating magnetic field,  it essentially flywheeled to a stop, wether or not we extracted electricity from it.

The experiment was to show the difference between the disk rotating above the magnet, and the disk rotating WITH the magnet. Voltage/Current are constant, but with a stationary magnet, there is negative forces when electricity is drawn.
as far as back  EMF from a pair of leads... that value is so rediculously small that it appears minute even to the drag effects of friction from the surrounding air.

Moving the magnets with the disk in this manner does not alter the induction effect whatsoever.
the magnetic field remains stationary (provided that your shaft turns straight).


@ Argona - if i understood Tesla correctly, the spiral cut sections of his disk were not to raise the voltage,. but to raise the CURRENT. as it forces the current to flow around the disk. instead of finding "shorter" paths across the radius of the disk as it spins around. - granted the overall current flow, does make a spiral around the disk, not all of it travels in that path and there is a great deal of curent loss with a non-spiral-cut disk. - at least thats how it works according to Tesla.

Free Energy | searching for free energy and discussing free energy

Re: Homopolar Generators (N-Machine) by Bruce de Palma
« Reply #47 on: February 22, 2008, 05:03:52 AM »
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Offline PulsedPower

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Re: Homopolar Generators (N-Machine) by Bruce de Palma
« Reply #48 on: February 22, 2008, 10:29:15 AM »
Hi argona, I am a bit rusty on these machines but I did the math on a 120MJ one just for the fun of it years ago, it is nice to dream, 120 MJ in a package weighing less than 3 tonne would have been an interesting but expensive toy to build.

Quote
Btw , the spiral disk I believe was not for a higher voltage
But to counteract torque and reinforce the magnet?

It should reinforce the magnet, though it is far easier to put turns in the stationary return current path  as is done with self exciting homopolar generators, they only need a small current to start them. Navel Research Laboratories built a 10MJ unit in the mid 70's. Only a car battery to start it but the current in the magnet rapidly reached 170kA before the current was diverted into the load. Alas there was plenty of torque with the pair of 170 lb rotors @ 18000 rpm initial speed almost stopping in 1 sec. In pulsed power there are good reasons not to spiral the rotor conductor:
1 it increases windage
2 it reduces the burst speed and thereby the energy which can be stored
3 it increases the rotor resistance
4 it increases the rotor inductance

Putting the spiral (coil usually) in the current return path only increases the system inductance and this can be switched out on pulse delivery without reducing the magnetic field (the field will drop slowly as the current decays in the now shorted coil).

SmOkey2, that sounds like a decent sized homopolar machine what sort of current was it putting out? How was the torque measured? measuring the shaft torque or cradling the motor are the safest, cradling the homopolar machine can introduce experimental errors easily. Did you know that an iron disk works fine for long rise time applications, with the advantage of greatly reducing the reluctance of the magnetic circuit (more voltage less magnet)

The setup on the high speed machine (27k rpm) from memory was a single aluminium slab rotor around 14" diameter with lots of brushes which could be brought into contact quicky with the rim and shaft, special attention was made to bring the current return conductor close to the rotor (to reduce system inductance and therby decrease the current rise time) The magnet was an air cored solenoid fed from another homopolar generator and energized seconds before the power was required (keeping a 4T magnet energised any longer than necessary gets expensive both in power and cooling) All the homopolar machines I have read about have been pulsed power ones and they stop very fast once current (40kA to 1MA) is taken from them. Maybe the current you were taking from it was small, being a low voltage machine it takes many amps to get appreciable power from it. 

Over unity or not they are interesting machines for playing with high current :)

Offline sm0ky2

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Re: Homopolar Generators (N-Machine) by Bruce de Palma
« Reply #49 on: February 23, 2008, 04:33:29 AM »
the torque was measured as a function of RPM on the shaft, vs current draw on the DC motor, which was metered at the source.
this rating was within some % error of , but close to the manufacturers specs for those motors.

as far as the actual  measurements for voltage/current, i know we wrote them down, throughout several experiments in a table, for the lab project, but i couldn' tell you what the actual values were..  it could not have been over 100amps, with the equipment were using, We didn't have anything rated much higher than that. - though, to fathom a megaAmpere', i kind of wish we had!!

drawing current off of the disk did not make it stop spinning or even slow down when the magnets were attached to the rotating shaft

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Re: Homopolar Generators (N-Machine) by Bruce de Palma
« Reply #49 on: February 23, 2008, 04:33:29 AM »
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Offline PulsedPower

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Re: Homopolar Generators (N-Machine) by Bruce de Palma
« Reply #50 on: February 27, 2008, 12:23:43 PM »
@smOkey2, I was sure I replied to this thread a few days ago but the post has gone anyway 100 amps is a very light load especially as the generator would put out less than 5V at 1440 rpm That is why pulsed power applications run the rotors so fast, voltage is propertional to speed and field strength. The 1MA generator had 80 tons of rotors but much smaller generators have been produced which produce similar currents

Offline sm0ky2

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Re: Homopolar Generators (N-Machine) by Bruce de Palma
« Reply #51 on: February 27, 2008, 04:05:22 PM »
i dont have any way of moving 80-tons of mass as such high RPM,

but im sure i understood the principal that was being taught, as i have used this in other applications since, and it holds true in every case i have encountered it.
Unless there is relative motion between the source of the field and the inductor, there can be no
'back torque'.

Induction still occurs because the field is stationary.

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Re: Homopolar Generators (N-Machine) by Bruce de Palma
« Reply #51 on: February 27, 2008, 04:05:22 PM »
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Offline PulsedPower

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Re: Homopolar Generators (N-Machine) by Bruce de Palma
« Reply #52 on: February 28, 2008, 03:29:53 AM »
@SmOkey2
Quote
Unless there is relative motion between the source of the field and the inductor, there can be no
'back torque'.

While I don't believe the torque reaction in a homopolar is between the moving conductor and the magnet but rather between the moving conductor and the stationary current return conductor. There is still relative motion between the source of the field and the inductor, otherwise it would violate faradays law or no voltage would be induced. I suspect that you assumed that the rotor is still the source of the induced voltage when the magnets are fixed to the rotor? Draw the complete electric and magnetic circuits including the load and you will see the field lines of the now moving magnet cutting the stationary electric circuit before looping around and entering the back face of the rotor. If the rotor was making the voltage it would be possible to rotate the load and magnets with the rotor and dispense with the brushes. If you still have access to this aparatus remove the brushes and connect a 3V light across the rotor with some hot melt glue to secure it and the wiring to the rotor, run the unit and see if the light glows. This makes sense, if no relative motion of the magnetic to any conductor is required why does the rotor need to spin at all and why is the output voltage proportional to the rotor speed? Something to think about, FWIW this was problem in a first year physics text.

I mentioned ANU's 80 ton machine, it is a very old machine but togther from a surplus betatron magnet and some large steel disks, The university of texas had made much more compact machines which deliver similar current.

Offline sm0ky2

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Re: Homopolar Generators (N-Machine) by Bruce de Palma
« Reply #53 on: February 28, 2008, 05:22:52 AM »
@SmOkey2
Quote
Unless there is relative motion between the source of the field and the inductor, there can be no
'back torque'.

While I don't believe the torque reaction in a homopolar is between the moving conductor and the magnet but rather between the moving conductor and the stationary current return conductor. There is still relative motion between the source of the field and the inductor, otherwise it would violate faradays law or no voltage would be induced. I suspect that you assumed that the rotor is still the source of the induced voltage when the magnets are fixed to the rotor? Draw the complete electric and magnetic circuits including the load and you will see the field lines of the now moving magnet cutting the stationary electric circuit before looping around and entering the back face of the rotor. If the rotor was making the voltage it would be possible to rotate the load and magnets with the rotor and dispense with the brushes. If you still have access to this aparatus remove the brushes and connect a 3V light across the rotor with some hot melt glue to secure it and the wiring to the rotor, run the unit and see if the light glows. This makes sense, if no relative motion of the magnetic to any conductor is required why does the rotor need to spin at all and why is the output voltage proportional to the rotor speed? Something to think about, FWIW this was problem in a first year physics text.

I mentioned ANU's 80 ton machine, it is a very old machine but togther from a surplus betatron magnet and some large steel disks, The university of texas had made much more compact machines which deliver similar current.


dont confuse the 'source' with the field. a rotating disk magnet produces a stationary field.
relative to the field, the disk is spinning.
any moving field-lines relative to the return circuit would be a result of the EMF caused on the inductive surface of the disk, NOT from the magetic field - and this can be avoided by routing your wires at a different angle.
assuming the magnetic disk is polarized evenly, and not in sections, there is a stationary, uniform field sitting in space, as the magnet spins.


i could probably throw together a small unit if i find me a coper disk.
slap it between a pair of magnetron rings, and mount a shaft through it.....
resistor + LEDs...

tie it to multiple points around the outer edge of the disk to balance the load.
(since the brushes cannot slide when the entire circuit is moving)

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Re: Homopolar Generators (N-Machine) by Bruce de Palma
« Reply #53 on: February 28, 2008, 05:22:52 AM »
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Offline PulsedPower

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Re: Homopolar Generators (N-Machine) by Bruce de Palma
« Reply #54 on: February 28, 2008, 08:23:05 AM »
Quote
dont confuse the 'source' with the field. a rotating disk magnet produces a stationary field.
relative to the field, the disk is spinning.

 I have never heard that one before but lets assume for the sake of argument that it is true. What is the field stationary with respect to, the planet the solar system the galaxy? what happens if you move the source, does the field get left behind? If the field was stationary with respect to the planetary rotation axis just the act of putting magnets near wires would make high voltages For example near the equator he velocity of the earths surface relative to the rotation axis is around 440 m/sec, if a 1.5T magnetic field was put near a conductor it would produce 1.5X440 V/m, I think 660V for every meter of conductor perpendicular to the the earths rotation axis and exposed to a 1.5T field would have attracted some attention by now, the case for the solar system and galaxy voltages are even higher. If you say the the magnetic field is stationary relative to the earths surface, why? There has to be some reason for this field to pick this particular frame of reference over the countless other possibilities. Maybe the field is stationary with respect to the the sources rotation axis, why the field is uniform it has no concept of rotation axis and linear generators also work and these can't have a rotation axis. The most obvious frame of reference for a magnetic field is the source as there is actually some reason for the field to follow the source, it is produced by the source whether it be electron spin or current flowing in conductors.

The homopolar generator derives its voltage from the motion of a conductor in a magnetic field, it doesn't have to be a disk a conductor travelling in a straight line though a field will produce a voltage. FWIW the Voltage is calculated by the equation e=LBV where e is the induced voltage, Length in Metres of the conductor perpendicular to the direction of travel B is the field strength in Teslas and V is the velocity of travel in metres per second. The faraday disk or homopolar generator came out of Faradays work involving motion of a conductor in a magnetic field it obeys exactly the same laws.

Quote
i could probably throw together a small unit if i find me a coper disk.
slap it between a pair of magnetron rings, and mount a shaft through it.....
resistor + LEDs...

tie it to multiple points around the outer edge of the disk to balance the load

No need to balance the load the resistance of the disk is negligable, also there is no need to use copper even iron disk machines can put out MA. It doesn't even need to be a disk, a single spoke on a shaft rotated in a field will produce exactly the same voltage, a disk is used becuase it is easy to pick up current off, easy to balance and has a lower resistance than spokes.

As I mentioned a conductor moving in a straight line perpendicular to a magnetic field will also make a voltage, MHD generators and rail guns use this principle. Lets say you stick ten 30mm neos in a line to a bit of wood and stick a length of wire on top, if you lay the stick across the seat of a car and go for a drive, will there be a voltage produced? This is exaclty the same scenario as the rotating magnet Homopolar generator, if the theory of the stationary field is true the voltage will be 24.5 m/s x 0.3m x 1.5T or 11V at 55mph I say no because there is no conductor motion with respect to the magnetic field, if you had 2 sliding contacts behind the car and hooked up meter to them you would see the 11V but this is not very practical. hence the popularity of the disk rather than the linear setup.

You are forcing me to revisit old physics books :)

Offline Gearhead

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Re: Homopolar Generators (N-Machine) by Bruce de Palma
« Reply #55 on: February 28, 2008, 03:24:26 PM »
Quote
dont confuse the 'source' with the field. a rotating disk magnet produces a stationary field.
relative to the field, the disk is spinning.

 I have never heard that one before but lets assume for the sake of argument that it is true. What is the field stationary with respect to, the planet the solar system the galaxy?


The fact that rotating the magnet with a stationary disk produces no electrical potential leads people to the conclusion that the field itself is stationary.  This has never been proven even though Faraday did numerous experiments in this line.  Tesla thought that the magnet did not contain the magnetism but was merely distorting the field around it, the ether theory.

It is interesting that when the space shuttle broke a long tether that it glowed with potential so that it could be seen for more than 100 miles due to the effect of moving through the magnetic field of the earth.

http://en.wikipedia.org/wiki/Faraday_paradox
"The magnetic field will be independent of any rotation of the magnet. In this configuration, the polarisation is determined by the absolute rotation of the disk, that is, the rotation relative to an inertial frame. The relative rotation of the disk and the magnet plays no role."

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Re: Homopolar Generators (N-Machine) by Bruce de Palma
« Reply #55 on: February 28, 2008, 03:24:26 PM »
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Offline argona369

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Re: Homopolar Generators (N-Machine) by Bruce de Palma
« Reply #56 on: February 28, 2008, 04:19:27 PM »
Quote
dont confuse the 'source' with the field. a rotating disk magnet produces a stationary field.
relative to the field, the disk is spinning.

 I have never heard that one before but lets assume for the sake of argument that it is true. What is the field stationary with respect to, the planet the solar system the galaxy?


The fact that rotating the magnet with a stationary disk produces no electrical potential leads people to the conclusion that the field itself is stationary.  This has never been proven even though Faraday did numerous experiments in this line.  Tesla thought that the magnet did not contain the magnetism but was merely distorting the field around it, the ether theory.

It is interesting that when the space shuttle broke a long tether that it glowed with potential so that it could be seen for more than 100 miles due to the effect of moving through the magnetic field of the earth.

http://en.wikipedia.org/wiki/Faraday_paradox
"The magnetic field will be independent of any rotation of the magnet. In this configuration, the polarisation is determined by the absolute rotation of the disk, that is, the rotation relative to an inertial frame. The relative rotation of the disk and the magnet plays no role."


Actually, it now looks possible (maybe) to have a true one piece
Homopolar generator that I?ve been discussing here,

http://tech.groups.yahoo.com/group/free_energy/message/30766
« Last Edit: February 28, 2008, 04:43:19 PM by argona369 »

Offline sm0ky2

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Re: Homopolar Generators (N-Machine) by Bruce de Palma
« Reply #57 on: February 29, 2008, 05:10:52 AM »
want to prove that the field is stationary?
rotate the magnet over another magnet, or over some iron filings... were the field not stationary, the field movement would affect these things would it not?

Tesla may have been right, the eather has never been disproven. Einstein's experiment only applies to light, you can do the same trick using sound to prove that air does not exist...
it has no bearing.

I would tend to agree that the magnet does not contain "magnetism", it contains energy - in its molecular structure - imparted upon it by a stronger field, alligning and amplifying the field produced by its cummulative electron orbits. - which causes a distortion-field.

wether or not this distortion occurs in a vacuum, or through an aether is not yet known. To know that, we would first have to devise a means of distinguishing an eather, that permeates everything.
how would we even go about doing such? would it matter if we did?

Offline Gearhead

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Re: Homopolar Generators (N-Machine) by Bruce de Palma
« Reply #58 on: February 29, 2008, 06:36:52 AM »

wether or not this distortion occurs in a vacuum, or through an aether is not yet known. To know that, we would first have to devise a means of distinguishing an eather, that permeates everything.
how would we even go about doing such? would it matter if we did?

There may be a simpler answer.  The magnetic field may dislodge electrons that are collected or moved by the centrifugal force of the disk conductor. However, this brings up the question of inertial field of reference.  How does the disk know that it is spinning?  Obviously this proves a connection with the rest of the universe, spacetime or whatever.

Offline sm0ky2

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Re: Homopolar Generators (N-Machine) by Bruce de Palma
« Reply #59 on: February 29, 2008, 07:22:52 AM »
i disagree there, 

i think the disk is moving relative to the magnetic field.
i dont think this effect can occur any other way.


the charge separation on the disk is relative to both the strength of the field, and the rpm of the disk.

so, a disk spinning in free air, WOULD produce a charge - because of the earths magnetic field.
however, the RPM would have to be considerably high.... and may exceed the tensil-strength of some disks...

 

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