coils and magnets

[blueyonder]

 getting on now as a newbie and getting to understand the terms.

 but this is how i see it working.

 north magnet passies coil .makes ac.

 south magnet passies coil makes  ac.

  so dos each magnet make its own bit for ac.

  so what would happen if you made a rotor with just the same ends of the magnets.

  so with single rotor and all north magnets.

  what would you get out.

  and the same on a differant mill this time all poles south.

  would the coils still make ac.

  my spongy brain is asking me if it will be dc out.

 if i had magnets with a screw hole in them i would try.

  just for my own interest. but gluing them to a disc would be so much work .

  so its better i ask.

 i am not meaning a twin rotor . just thinking about a single rotor.

  if you get a new software setup . can i change my user name to spongey brain or has that one allready got a user.

 posted as homebrew electric . must be in the right shop i think.

   

moved to newbies because this is asked like every couple months by just about every newbie to come through here.
Kurt

[cutlass1972]

as one pole passes by the coil you get one half of a sine wave, then as the other pole passes you get the other half of the sine wave.

If you only passed one pole across the coil repetitively you would get one half of a sine wave over and over again, weither it be positive or negative.

what we are talking about would be called pulsating dc

[spinningmagnets]

The way I understand it (I'm still a newbie, too) I would use a visual model of one oval coil with three round magnets. The magnets are side-by-side and spaced close together as if they were on a rotor, and they were three of the magnets from a 9-coil/12 magnet Permanent Magnet Alternator (PMA)

Electrons can be pulled out of an atom, and also pushed into an atom. Electrons have a negative charge. The north pole of a magnet also has a negative charge, and the south pole of a magnet has a positive charge.

"Opposites attract" like when the north pole of one magnet is strongly attracted to the south pole of another magnet. "Like charges repel" just like when two north poles of two magnets push away from each other.

For this example the spinning magnet rotor has the "S" of the first magnet facing the coil, the second has the "N" facing the coil, then the third has the "S" facing the coil. The coil will see them in a S-N-S order, and the rotor is spinning clockwise like a plate in front of you at the dinner table, with the coil under the top edge of the plate with the two wire leads radiating up at about 11 o'clock and one o'clock.

The two long sides of the coil are the "legs" and that is where the magnets fly past.

when the first and second magnets are over the two legs, the S magnet face is pulling electrons in one coil leg, and the N magnet face is pushing electrons in the other coil leg. This creates a pulse of electron flow in one direction. (Clockwise)

Then the spinning rotor moves a bit farther, which moves the N magnet face from one coil leg, to over the other coil leg. Then the last S magnet face moves onto the first coil leg. This movement of the rotor ends up putting magnets over the two coil legs that are the opposite magnet pole order of what is was a moment ago. This creates a pulse in the opposite direction out of the two lead wires coming from the coil. (counter-clockwise)

In this way, an alternating direction of electron flow pulses is created in the oval coil (clockwise, counter-clockwise).

I hope I understand this reasonably correct, and have explained it in a "useful" way.

[Flux]

This is too complicated to go into much detail, there is no simple answer, too much depends on the details of construction.

Firstly let's get rid of the obvious misconception, there is no way you will get dc out of this. All machines that produce dc have sliding contacts, nearly all generate ac and rectify ( commutator) the special homopolar machines based on the Faraday disc still need brushes and sliding contacts.

You can make perfectly satisfactory unipolar alternators, but they are essentially conventional machines with half the poles left out, they need to be wound as though these poles were still present. The flux changes from maximum to zero, it doesn't reverse but the output is still ac. The actual waveform depends on the construction but it is normally not significantly changed.

This is not an ideal place to learn about conventional electrical machines, even the common 3 phase alternator met here is very strange, with considerable parts of the stator not wound( it's just a convenient construction for simple air gap axials).

Unless you want to understand the theory of strange machines it is easier to just accept what everyone else does, Virtually every conceivable idea was tried before 1900, you are unlikely to make a radical new discovery, but it pays to look at the old ideas as many were only rejected by the limited technology of the time, particularly magnets,

The axial flux alternator was one of the earliest and the improvement in magnets has brought it back into favour for wind power and it may make a comeback in other fields.

Flux

[electrondady1]

blue yonder did you get your stator out of the mold ?

[finnsawyer]

If you connect a coil up to an oscilloscope and move it past a North pole you might see a positive voltage pulse followed by a negative pulse.  If sometime later the coil moved over a South pole you would get a negative pulse followed by a positive pulse.  The zero crossing in both cases occurs when the coil in exactly centered over the magnet.  Somewhere on this site is a posting showing such a case.  The link is lost to me.  If anyone finds it I'd like to have the link.

To continue, the ac is sort of there and each coil interacts with the magnets independently of the others.  This behavior is the basis of the alternator design you will find here:

     http://www.fieldlines.com/story/2006/4/21/16237/9933

In the case of the 3 phase alternator when a coil is exactly centered over a magnet, its voltage will be zero (the zero crossing).  As the coil moves (or the magnets actually) over to the next magnet it interacts with both magnets.  The voltage of the coil is the sum of the voltages it would get from interacting with each magnet by itself.  The result is a maximum or minimum voltage when the coil is exactly straddling the two magnets.  A positive voltage pulse is followed by a negative pulse and so on as the rotor turns giving the familiar ac voltage waveform.

[wooferhound]

I think this is the link you are looking for . . .

http://www.fieldlines.com/story/2004/10/2/11043/6778

[blueyonder]

 THANK YOU . i got a lot of info from the replys.

 its terrible when sumthing floating around in the brain and wanting a answer.

  i said in a post before not long ago . my total knowledge about electrics as generating gos .

  it is 1%.  but now its 2% . a 100% increase.

  i am not a stranger passing through town.  i hope im here to stay.

   i have other interests in RE got a solar panal up now for two winters and one summer. a 70 watt and 20 watt.

    other thing im messing with is a solar water heater.

  but now i got to wait on next years sun before i can make the mark 2

  the uk is not the best plase for solar.

  but cant complain cos the weather is good for this time of year .

 last week it only rained two times. once for three days and other time for four days.

   thank you Gentelmen for your kind help in me understandind  just what is going on.

    menny thanks  

[finnsawyer]

Nope.  Good try though.  The posting that I'm looking for shows exactly what I described above, a positive pulse followed immediately by a negative pulse on the scope.  What the poster did was mount a single coil on the stator and a single magnet on the rotor.  So, while the waveform repeats, there is a time of no voltage between the active parts of the waveform.  This is a more accurate portrayal of what actually happens in an alternator than my explanation with the linear motion, but the difference isn't all that significant.

[kurt]

at one time i drew out how the magnets interacted with the sign wave in simple terms let me see if i can resurrect it here

[Kevin L]

Has anyone tested standing the coils on edge with a small gap?