magnetic flux / faraday disc idea . / General Science and Electronics / Forums

Forums

4hv.org :: Forums :: General Science and Electronics

« Previous topic | Next topic »

magnetic flux / faraday disc idea .

first previous 2 3 4 5 next

Move Thread

LAN_403

Salvador

Sat Sept 19 2015, 10:21AM

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

Ok, i agree Uspring , it requires part of the loop moving and part being stationary or moving with a different speed.
Here is some further thinking.I will post a picture to illustrate better what I mean.

So let's get back to the original faraday disc, assume the disc is excited with AC type magnetic field , first of all I want to ask to make it more productive , can I just add two discs close to each other with a ferrite (high frequency) or silicon steel (lower frequency) part inbetween them and arrange the field coil in such a way that the flux lines go N-S through the first disc and S-N through the second , in other words the middle material between the two discs would have the N pole of the field coil entering it and the S poles would be linked to come in the material from each side going through the disc ,if this could be done the current would flow from ceter to rim in the first disc and back from rim to center in the other, so the both connections (brushes) could be made at the shaft were rotational speed is less.

But here I want to go even further in my thinking quest, forget the brushes for a while, imagine this, what would happen if instead of having brushes I would make a rotational capacitor,And if this two disc layout would work each of the plates could be attached to each end of the disc/s , theoretically if the discs are excited with varying magnetic field the carges in the disc should feel a force an should attract and repel to each of the capacitor plates forming a current.
I guess this also begs the question if excited by AC field does the faraday disc work solely on lorentz force or does it not exhibit both lorentz force and also induction , I think the latter is true.

so technically if the capacitors are formed and an ac field is used as the exciter field , for simplicity we could assume the field coil is in series with the capacitor output , once the disc begins to spin one could use a small permanent ,magnet to excite the first current then the current would flow until the capacitor is charged , then the current would stop both in the field coil and in the disc also the field would collapse , but then the capacitor would start to discharge forming the field with opposite polarity and then second half of the cycle would begin as the disc continues to spin now the capacitor would get charged the opposite way and so this oscilation should continue as long as mechanical force is supplied to spin the disc ,
what do you think?

Now i realize the drawbacks that even if this works in theory , the capacitor surface area would be small and the capacitance would also be small so the disc would have to have a high frequency.

the drawing is kinda crude , I hope you can understand the vague idea that it tried to portray

Ash Small

Sat Sept 19 2015, 11:48AM

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

Looks like we're back with conventional alternators now.

The dynamo is a circuit where part of it moves, and part stays still. It also requires brushes.

Until silicon rectifiers became available (well, before germanium rectifiers, anyway) dynamos were used in vehicles.

The main drawback of the dynamo is that the brushes wear out. They also tend not to be as efficient as alternators.

If it were possible to build a 'brushless dynamo', it should have been invented a century ago.

Salvador

Sat Sept 19 2015, 12:59PM

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

I am thankful for any response but , this is still a faraday disc not a conventional alternator, because the latter ones work :d

Also , I was interested to know about the capacitor idea , not that I hope to achieve something here , I mean I'm just a random nobody, but i am interested anyways no matter what , that the reason I ask.

Are you saying that in the faraday disc with a varying magnetic field isn't any charge flow or accumulation? but in a capacitor charges also just accumulate they never cross the dielectric , it's enough if they feel the forces from one another , why wouldn't they flow here in the presence of a time varying b field to the capacitor back and forth ?

Ash Small

Sat Sept 19 2015, 02:53PM

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

Post deleted

Salvador

Sun Sept 20 2015, 06:31PM

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

anyone please? Oh and by the way why does it say post deleted what was in that post Iwould like to know?

Dr. Slack

Sun Sept 20 2015, 06:45PM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

Salvador wrote ...

I am thankful for any response but ...

The problem with these machines you keep inventing is that

a) if you are content with AC output, it's easy to do the conventional way, there's no need for obfuscated magnetic circuits
b) if you want a DC output, you *cannot* do it without some form of commutation, a coil permanently attached to the output wires cannot generate DC, as that would require a flux ramping continuously up to infinity.

Wastrel

Sun Sept 20 2015, 10:23PM

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

Ash, The fields of the two back to back magnets would not completely cancel and some field would shoot out the sides but it would be much reduced, yes.

Salvador, I don't see a difference between induction and the Lorentz force. The difference between a conventional motor and a Faraday disc is that the former varies the total magnetic field in a loop and the latter unbalances a loop with constant field by having one part of it move.

A resonant design could work as a generator but at some point for every coil the flux has to drop again and that means the voltage induced reverses. You cannot move an AC electromagnet inducing a DC into another coil, as Uspring and Dr.Slack have explained. It doesn't affect the EMF of the contactless Faraday generator because at every level of flux the EMF induced by the motion would still be balanced.

Ash Small

Mon Sept 21 2015, 01:44AM

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

Thanks for the clarification, Wastrel.

Wastrel wrote ...

I don't see a difference between induction and the Lorentz force. The difference between a conventional motor and a Faraday disc is that the former varies the total magnetic field in a loop and the latter unbalances a loop with constant field by having one part of it move.

Wikipedia says the 'Faraday Disc' was also known as 'Faraday's Paradox' because it couldn't be explained by 'Faraday's Law', and it was another 20 years or so before Lorentz arrived to explain it.

Any chance of a bit more 'clarification'?

Salvador

Mon Sept 21 2015, 07:26AM

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

@ Dr.Slack and Wastrel , yes I do realize that for a true DC output one must have sliding contacts and of all the DC machines I believe the one that really makes DC is only the faraday disc as the dynamo and any DC generator would become an alternator if the many separate contact rotating commutator would be exchanged for two slip rings. evenb with the commuator the output still pulses I guess that's why they make no less than 4 poles otherwise the ripple is too large.

What I actually want is an electromechanical amplifier so to sepak of, something that still functions as a generator (mechanical torque converted into electrical energy) but whose output frequency and also power can be controlled by an independant field made from a field coil and that frequency/field would not be dependant on the rotational rpm as it is in most or almoust every generator that I know of.

Now I believe if one takes the faraday disc with the alternating current field (a reference video was put in thsi thread somewhere earlier) it could work that way , because its a homopolar machine it still requires brushes though but its rotational rpm is independant from its output frequency , one can form an LC circuit for the field coil and feed it from the output but determine the frequency with a variable capacitor for example.So if one has low rpm one can just turn up the frequency so that the generator doesnt become useless.
Or so.

then the only mind quest I have is to think if there is any (alien or human :D) way to make a contactless faraday disc , now surely if excited by a DC (static) magnetic field there is no way to have it without contacts but if excited by a varying magnetic field is then there any chance for contactless operation ,
Now as a thought experiment take the capacitor idea , would it work atleast in theory what do you think? I do realize that because of the low surface area and other factors the capacitance attainable would be very small but the very concept could it work that way ?
the way I see it is take for example one half period of the AC wave that excites the field in this generator , the charges on the spinning disc feel a force one way or the other because of the changing field, now those charge then start to flow , if the disc is not attached to anything they just form regions of higher concentration until the field stops changing, but if the disc is connected to a capacitor at each end , now the capacitor can be assumed as stationary even though one plate rotates but the surface area doesnt change so as the charges feel the force they would now go to the capacitor were they would pile up feeling the force from the opposite plate until the magnetic field stops changing then as it reverses polarity discharge happens and the capacitors are charged the opposite way.

Ash Small

Mon Sept 21 2015, 08:02AM

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

Salvador wrote ...

What I actually want is an electromechanical amplifier so to sepak of, something that still functions as a generator (mechanical torque converted into electrical energy) but whose output frequency and also power can be controlled by an independant field made from a field coil and that frequency/field would not be dependant on the rotational rpm as it is in most or almoust every generator that I know of.

You can excite an alternator using AC (or variable DC) and it will work as an amplifier, although ripple will be present, depending on RPM.

If you excite a Faraday disc with an electromagnet, the output will follow the input without ripple.

first previous 2 3 4 5 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob