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self excited homopolar generator (no PMM!!!)

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Salvador

Sun Apr 12 2015, 10:13AM

Registered Member #54402 Joined: Mon Feb 02 2015, 11:09PM
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Posts: 86

I understand how power is calculated , although I'm not quite sure what you meant by your last post Andy?

currently I'm not after anything , I just want to understand hoq does and if it works at all.

Ok I will try as simple as possible , one more time.

Imagine you have a solid one piece rotor with a magnet inside (no details just the idea) the magnet somehow is changing polarity at some certain rate , say 100hz.So the rotor has a AC magnetic field whose frequency is 100hz.For simplicity imagine this rotor is shaped much like that of an AC induction motor.
Now around this rotor is a stator which is wound like a toridal transformer , for easy imagine that the device looks similar to that if you would put the rotor in the middle of a real toroidal transformer.In other words the windings on the stator circle around the stator core like the ones on a toroidal transformer.

The idea was that as he rotor was spinning with it's AC field it would both induce current in the stator winding and also act as a homopolar machine because the magnetic field would be at the right angle and lorentz force would also push the current in the stator windings in each cycle.

The idea of combining the advantages of homopolar generator with an ac one, to get rid of the brushes, yet im not sure can a varying magnetic field rotated around a uniform winding exert lorentz forces in it like they happen in a rotating faraday disc that rotates in a magnetic field.

Uspring

Mon Apr 13 2015, 09:06AM

Registered Member #3988 Joined: Thu Jul 07 2011, 03:25PM
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The AC field will induce some voltage in parts of the toroidial winding, but I believe they will cancel with voltages induced around other parts of the toroid due to symmetry. I'm not so sure about the effect due to rotation, but I think there is no difference to a DC type rotor. My hunch is, that there is no voltage induced at all in sum along the complete toroidial winding.

Salvador

Mon Apr 13 2015, 12:59PM

Registered Member #54402 Joined: Mon Feb 02 2015, 11:09PM
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Posts: 86

But any toroidal transformer has the current going opposite directions at opposite sides of the torus. yet they still work.
basically even without the rotor in the middle , any toroidal core has opposite currents around it.
the field from the rotor basically encloses just the inner parts of the loops because the outer parts are further away and between them is the stator core material .
What doy you think maybe i got it wrong ?

But if not for the geometry would the specific idea work at all ? If the magnetic field which is changing is also at the right angle to a conductor can I get both induction and lorentz drag working together, so the current would be both created and boosted by firstly induction because of a changing magnetic field and also because of the lorentz drag as in a typical faraday disc?

radiotech

Tue Apr 14 2015, 07:38AM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
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But any toroidal transformer has the current going opposite directions at opposite sides of the torus. yet they still work.

Think of the core. Now wrap a few turns on one side. Identify the ends of the wire, as
start and finish, of the winding. Now on the same side, next the coil wind a second coil,
same as the first. looking at the four ends, the polarity will be + - , + - .

Now slide one of the coils to the other side. The polarity will be :

side 1 + -

side 2 - +

Is this what you mean ?

Uspring

Tue Apr 14 2015, 08:10AM

Registered Member #3988 Joined: Thu Jul 07 2011, 03:25PM
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Salvador wrote:

But any toroidal transformer has the current going opposite directions at opposite sides of the torus. yet they still work.

What matters is the direction of the field relative to the handedness of the winding. At opposite sides of the toroid, the direction of the field is opposite, but relative to the handedness of the winding it doesn't change.

Maybe your intent is to conceive a DC generator without brushes. I don't have any idea, how that would work. The working of a homopolar generator relies on the fact, that one part of the loop, where the voltage appears, is moving, i.e. the disk, and the other part, i.e. brushes and wiring to the load is stationary. So there will be Lorentz forces on the moving part and none in the wiring. This won't work without brushes.

For a fixed disk and a rotating magnet as in the video, there will be Lorentz forces on all of the loop, but they will cancel to 0.
An AC magnet might induce voltages in the loop, depending on the orientation of the loop, but the induced voltages will be AC.

radiotech

Tue Apr 14 2015, 03:34PM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
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Induced voltage need not be alternating, but it certainly will be changing. I believe
that is what Faraday discovered.

Salvador

Tue Apr 14 2015, 06:11PM

Registered Member #54402 Joined: Mon Feb 02 2015, 11:09PM
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I'm sorry radiotech but i couldn't understand exactly what you meant by yout previous post, No I mean I totally got the idea of what you were saying but couldnt figure out which side is which by the pluses and minuses.
Anyway I think Uspring already got what I'm talking about , because DC has a static field which cannot do work on systems that aren electrically connected to the current source so it menas that there cannot be a DC brushless generator , much like a DC brushless motor used in little pc fans is actually a switched AC induction motor.I guess they call it DC because it is supplied with DC and that's it.

But Uspring you also got closer to what I am trying to do with your last post, well maybe we cannot create a truly DC brushless generator but we can use AC and create a generator which both has induction properties as any AC machine but whose load windings are also boosted by the same lorentz drag found in a faraday disc that was my idea.And if the field coil has capacitor controlled high frequency AC we could make a small yet efficient and powerful machine.this was what Im after.

I need the toroid thing with its one output winding and the dishes and field coil to be able to control the induced frequency with an adjustable capacitor , as in a normal AC generator the frequency is dependant on the speed of the rotor because it uses DC poles with a dc field which is then rotated and as many times it passes a load coil such is the frequency. I washaving a but different take on this whole thing.
Tell me do you understand the idea now? And would it work?

Uspring

Wed Apr 15 2015, 10:26AM

Registered Member #3988 Joined: Thu Jul 07 2011, 03:25PM
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Posts: 711

Induction effects as described by Faradays law and the Lorentz force are the same thing. The Lorentz force appears, when a charge is moving or when you look at the magnetic field from a moving reference frame. So you don't have both. Think e.g. of a wire loop rotating in a magnetic field:

You can calculate the induced voltage from Faradays law. You'll get a voltage, since the magnetic flux through the loop changes.

You can also calculate the voltage from the Lorentz force. You'll get a voltage since you have a wire moving through a magnetic field.

Both of these voltages will be the same, but you mustn't add up both to get the right voltage. In a homopolar motor with an AC field, things become somewhat complicated. One has to take care not to double count voltages here.

Rotating a loop in an AC magnetic field is best calculated by just using Faradays law. You should not add Lorentz force effects here.

Salvador

Thu Apr 16 2015, 08:28AM

Registered Member #54402 Joined: Mon Feb 02 2015, 11:09PM
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So it seems taht the only generator that uses only lorentz effect alone is the homopolar generator /faraday disc?
because even a traditional dc generator with commutator has a slightly varying magnetic field in it's coils even at the output , the very reason actually why they make 4 and more poles on the rotor is for the output waveform to have as little variation as possible yet it's still not flat DC, corect? so a typical DC generator with rotor and commutator is still basically a somewhat AC machine and induction applies to it ?

Uspring

Thu Apr 16 2015, 03:49PM

Registered Member #3988 Joined: Thu Jul 07 2011, 03:25PM
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Posts: 711

Yes, yes and yes.

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