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magnetic flux / faraday disc idea .

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Salvador

Sun Sept 13 2015, 11:49AM

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

I was talking this to one other fourm , not much luck there except the conclusion that it somehow would not work the way i think it could but ok, let me explain it here and see what you guys think.

So we know that the faraday disc (the only true DC generator) works only when part of a conducting loop rotates in a homogeneous magnetic field which requires sliding contacts , brushas at all cases.
Now I'm going to post two pictures and divide this idea up in two parts.
Firstly Imagine i take the disc and cut it up like a pizza in many separated straps of conductor, more like wires that would normally run from the center to the rim or outer perimeter.Now take a N-S magnet , not a disc magnet but a strip of magnet that only covers at most a few of these strips of copper at any time.Now rotate these magnet from both side of the cut up disc and as they would pass each of the strips the strips would get induced current.
Now even though i wouldn't need brushes anymore , obviously each of the strips would need to be electrically separate as if i connected them together the current would cancel in the other ones and so on.
So this version wouldn't make a good generator, so here we go to the next idea.

So take a toroid like core and wrap a coil on it , wires coming one way and at the opposite side going dow the other way to come back up again.
you take magnets and a rotor and somehow make the inner core on which the coil sits one pole say N for example , while the rotor whose blades rotate pas the coil on each side S, at the inner toroid side the toroid has an extension with an airgap with the rotor were the field lines go back into the toroid once they went through the rotor blades into the rotor shaft.
what do you think?

Ash Small

Sun Sept 13 2015, 12:59PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Shouldn't be difficult to test it, I've a large toroid woth a few hundred turns on it, I'll see if I can find it and some neodymiums.

I have a suspicion that the magnetic field lines in the toroid cancel each other, though. Have you seen 'the world's simplest electric train' video?

Salvador

Sun Sept 13 2015, 01:56PM

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

oh Hi there Ash.I haven't seen that video for a long time , very neat little thing.
as for the toroid , thanks for taking your time to experiment , it is interesting but in the many times i have thought over it , I think there are some important things to consider , first of all for the flux to be at the right angles between the rotor blades and the wire/toroid core , all of the toroid core must be exposed to the flux , like imagine a bar magnet being attached at the inner side of the toroid window one pole to the toroid the other pole facing the rotor shaft so that one pole goes into the toroid core and the other pole extends into the rotor shaft which has those blades at the end and the flux just goes through them back into the rotor , and as the rotor moves the field lines are being dragged around along the surface of the coil ,
but at everytime one pole should face into the toroid core while the other must face into the rotor and the rotor being a low reluctance path will point that field back into the toroid core.

in other words here the toroid core serves the purpose of having something on which one can hold the coil and hence the same pole comes in from both sides the field points in opposite direction at each side which is important otherwise the currents would cancel out at each loop.

what do you think, do you understand my thought picture?

Wastrel

Sun Sept 13 2015, 03:28PM

Registered Member #4095 Joined: Thu Sept 15 2011, 03:19PM
Location: England.
Posts: 122

"make the inner core on which the coil sits one pole say N for example"
If you could do that it would work. You can't do that.

Salvador

Sun Sept 13 2015, 04:35PM

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

pardon me, my wording wasnt at it's best, well I should have said not to make the inner core only one pole but to make the flux going through the coil at the right angle, I think that is all that matters for induced current in a coil?

I mean say we have a field coil located the way I described the bar magnet would be located.the field lines exite one side of the coil enter the rotor for example go through the shaft through the blades that face the toroid into the toroid cutting the coil that sits on the toroid at 90 degrees , then through the toroid the field goes back into the coil attached between the toroid core and the inner part of the toroid window were it has an airgap with the rotor shaft.

Conundrum

Mon Sept 14 2015, 06:28AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

IIRC it needs brushes because otherwise any possible configuration of disks will cancel out any generated current.

There is a way to use a plasma system to conduct energy though, using the negative resistance of a streamer in neon with an edge conductor made of a low work function specialty reticulated vitreous carbon for minimum possible resistance.

I am probably going to get in trouble with the DoD as they actually (probably) use this method on the rail gun prototypes.

Salvador

Mon Sept 14 2015, 11:29AM

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

interesting thoughts Conundrum but , as I pointed out myself the faraday disc in all of it's geometrical forms whether a disc or a cylinder or whatever needs brushes.
But here with the toroid coil it's not exactly a faraday disc anymore , so the hope is to be able to get the desired output following input signal as in the faraday disc but with an AC type induction system.
the coil sitting on the toroid should see a continious yet polarity and location changing magnetic field running along the lengths of the coil.

I'm still inerested to hear if Ash has something to say about this , if he has tested it.
sadly I dont have a large toroid on hand right now.

Ash Small

Mon Sept 14 2015, 12:44PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

I'm still trying to work out how to get a 'south pole' at the centre of the toroid. Best idea I can come up with is to place a south facing side of a neodymuim against either side of the toroid 'hole', and place north facing sides of more neodymiums at the periphery, and then spin the magnets. I'd need to leave space for the wires to exit. You can get neodymuims with holes in the centre, so I suppose something could be bolted together to try it, but I don't currently have any neodymiums with holes in the centre.

Salvador

Mon Sept 14 2015, 05:22PM

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

well the way I invisioned this could be done like in the attached picture, the magnets are arranged so that alike poles run into the toroid while the other two alike poles face the rotor , the rotor being a low reluctance material allows for the majority of the field to go through it and back into the toroid core were the rotor extensions (blades) face the toroid surface, the flux then enters the toroid at 90degrees angle which when rotates cuts the wires sitting on the toroid.
what do you think?

Ash Small

Mon Sept 14 2015, 05:38PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

I think you could try it with a stack of neodymiums bolted together with opposing 'souths' in the centre, and use some bearings and bolt some arms on to support more stacks of neo's with opposing norths at the periphery, but you'd need a gap to support the toroid and for the wires to exit.

I' don't know how good the magnetic coupling will be with all those big air gaps, though.

I suppose the idea is to get the toroid near to saturation. I'm not sure how successful that will be.

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