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### Author Topic: Homopolar generator idea  (Read 11703 times)

#### F6FLT

• Sr. Member
• Posts: 405
##### Re: Homopolar generator idea
« Reply #15 on: March 04, 2019, 11:30:33 AM »
The voltage depends on the direction of rotation and the polarity of the magnet.
If on one side we see the pole N turning CW, on the other side we see the pole S turning CCW. So the effects are compensated, the voltage is the same on both sides.

No one has yet found a way to add voltages of a homopolar generator without going through as many sliding contacts as rotating elements, which is why we do not know how to make homopolar generators generating a high voltage, whereas it is very easy to do so with alternating currents, simply by increasing the number of turns of the coils.

The patent https://patents.google.com/patent/US6603233B2/en is an example of the increase in the voltage of a homopolar generator, but by the multiplication of sliding contacts. The sliding contact being the weak point of any homopolar generator because it is too resistive when the domain is that of low voltages and high currents, multiplying them multiplies the problems without innovating anything on the theoretical level (contrary to what its promoters say by insinuating violations of Newton's laws or relativity  ).

• Sr. Member
• Posts: 311
##### Re: Homopolar generator idea
« Reply #16 on: March 04, 2019, 11:35:22 AM »
I made a test with a disappointing result

Regards Arne

Ps: F6FLT Posts: 345

#### phoneboy

• Jr. Member
• Posts: 76
##### Re: Homopolar generator idea
« Reply #17 on: March 04, 2019, 03:53:30 PM »
@F6FLT, have a design/mod/expansion of Teslas unipolar dynamo on paper.  It's brushless, strengthens its field as current is taken off, and you can add resistance to determine voltage.  I never posted or worked up cad drawings for it as i knew i wouldn't havd time to build it (other projects).  Also, didn't think it would get much traction either as it works on situation # 2 of the paradox where the magnets move with stationary disk.  If anyone is interested I guess i can whip up something in sketchup (trying to learn fusion/inventor), just dont expect it fast.

#### F6FLT

• Sr. Member
• Posts: 405
##### Re: Homopolar generator idea
« Reply #18 on: March 04, 2019, 05:08:54 PM »
@F6FLT, have a design/mod/expansion of Teslas unipolar dynamo on paper.  It's brushless, strengthens its field as current is taken off, and you can add resistance to determine voltage.  I never posted or worked up cad drawings for it as i knew i wouldn't havd time to build it (other projects).  Also, didn't think it would get much traction either as it works on situation # 2 of the paradox where the magnets move with stationary disk.  If anyone is interested I guess i can whip up something in sketchup (trying to learn fusion/inventor), just dont expect it fast.

It must be understood that "sliding contact" is just a way of talking about an electrical contact between two conductors that move relative to each other.
Two counter-rotating discs that touch each other by their rim make a "sliding contact" in the electric sense, even if nothing really slides mechanically. Because I assume you're talking about Tesla's patent 406968. This does not derogate from the rule that a sliding contact is required every time you want to increase the voltage without increasing the speed. With two counter-rotating discs, the relative speed has been doubled, it's only a practical way to do it but it remains a classic homopolar generator with its two half-circuits in relative speed.

If your design is based on a different idea, even partly based on this patent, I'm interested and would appreciate that you give a description.

#### F6FLT

• Sr. Member
• Posts: 405
##### Re: Homopolar generator idea
« Reply #19 on: March 04, 2019, 05:15:42 PM »
@Arne

Could you give a brief description? I don't really understand the principle.

#### phoneboy

• Jr. Member
• Posts: 76
##### Re: Homopolar generator idea
« Reply #20 on: March 04, 2019, 05:37:26 PM »
ok, i'll wip up some drawings, prob be a couple days

• Sr. Member
• Posts: 311
##### Re: Homopolar generator idea
« Reply #21 on: March 04, 2019, 05:39:38 PM »
@Arne

Could you give a brief description? I don't really understand the principle.

I created a bunch of overlapping consecutive pulses that made the transistors go low (ON) one after the other in a row, (on resistance 3 - 4 ohm) instead of a brush sweeping around (a part) of the  copper disc.
Regards Arne

#### F6FLT

• Sr. Member
• Posts: 405
##### Re: Homopolar generator idea
« Reply #22 on: March 04, 2019, 07:27:54 PM »
I created a bunch of overlapping consecutive pulses that made the transistors go low (ON) one after the other in a row, (on resistance 3 - 4 ohm) instead of a brush sweeping around (a part) of the  copper disc.
Regards Arne

It can't work because the charges have to move for Lorentz's force to operate.
If you analyze from an electrical point of view, all the points of the disc are equipotential (ground potential). Your switched circuits connect two points of equal potential, so there is no current.

I recently thought of experiments to replace the mechanical movement of charges with a current, to make a solid-state homopolar generator from an alternating current that would simulate rotation, especially in dielectrics. I tried and failed. Nevertheless, I think this should be possible.

#### shylo

• Hero Member
• Posts: 540
##### Re: Homopolar generator idea
« Reply #23 on: March 05, 2019, 12:45:14 AM »
what creates the potential,  the disc spins in the magnetic field,
the field causes movement of the free electrons in the disc's molecules?
the farther apart the collection points (the stator),the greater the potential?
If you put more collection points in place does that just divide the potential, resulting in the total sum?
artv

#### F6FLT

• Sr. Member
• Posts: 405
##### Re: Homopolar generator idea
« Reply #24 on: March 05, 2019, 09:32:48 AM »
what creates the potential,  the disc spins in the magnetic field,
the field causes movement of the free electrons in the disc's molecules?
Yes, the Lorentz force forces the electrons to move perpendicularly to their speed vector, e.g radially.

Quote
the farther apart the collection points (the stator),the greater the potential?
If you put more collection points in place does that just divide the potential, resulting in the total sum?
artv
The  potential is not the cause of the current but the effect. The Lorentz force on the electrons, therefore a current, is the cause. This force depends only on the charges, their speed and the B field. Of course if your disk is larger, with a magnet of same size, you will have more moving charges thus more current.

#### shylo

• Hero Member
• Posts: 540
##### Re: Homopolar generator idea
« Reply #25 on: March 05, 2019, 06:34:19 PM »
the voltage is a result of electrons being forced to move inside the disc which has it's own resistance?
Voltage=Current(electron flow)x resistance?
Do the stators contact points absorb all of the moving electrons,or can we add more collection points?
Or since there is only a given amount of resistance, there can only be a given amount of flow?
artv

• Sr. Member
• Posts: 311
##### Re: Homopolar generator idea
« Reply #26 on: March 05, 2019, 08:33:09 PM »
,or can we add more collection points?
Or since there is only a given amount of resistance, there can only be a given amount of flow?
artv

I've tried with four collecting "brushes" (2 + 2).
Nothing extra only more brush braking.

Regards Arne

#### Belfior

• Hero Member
• Posts: 562
##### Re: Homopolar generator idea
« Reply #27 on: March 05, 2019, 11:15:13 PM »
what if you just make notches on the wheel? To make the current pulse

Then make one coil in the rotor and then another coil in the stator. Would that not gather the current and no need for brushes?

#### F6FLT

• Sr. Member
• Posts: 405
##### Re: Homopolar generator idea
« Reply #28 on: March 06, 2019, 11:44:22 AM »
the voltage is a result of electrons being forced to move inside the disc which has it's own resistance?
Voltage=Current(electron flow)x resistance?
Not exactly. The electric field that electrons feel is E=VxB (vector product, V their linear speed, B the field). This has to be integrated along the radius to get the voltage because V=∫E.dl.
Say v=10m/s at the half-radius, B=1T, disk radius = 10 cm, then V ≈ 0.5V.
Then I=V/R gives you the short-circuit current.

Quote
Do the stators contact points absorb all of the moving electrons,or can we add more collection points?
Or since there is only a given amount of resistance, there can only be a given amount of flow?
artv
I don't understand the question. The contacts simply add a resistance in series in the circuit.

#### F6FLT

• Sr. Member
• Posts: 405
##### Re: Homopolar generator idea
« Reply #29 on: March 06, 2019, 11:48:19 AM »
I've tried with four collecting "brushes" (2 + 2).
Nothing extra only more brush braking.

Regards Arne
That's why in Tesla's patent brushes at not on the rim. The rim is the worst position for brushes because the speed is maximum and so is the friction.