Unconventional Thought

[Spdlmt150]

I am throwing out an idea to see if I might be missing something. If the 12/9 configuration is altered to use 24 magnets, 9 coils.... What I drew up is the 1.25 X .562 magnets.

Would this effectively decrease the amount of copper not producing current? Less resistance? Narrower coils I would think would be more efficient. Possibly be able to get away with less wire - thinner stator.

Nothing here is known for sure... Just an idea I had. To all the gurus: Let me know how far off I am with this.

I know the .125 thickness magnets are too thin for this kind of project. If they were .25 thick with the same length & width?

[Countryboy]

I'm not sure I follow what you are trying to figure out.  What exactly is your end goal?  Are you just trying to figure out how to use the copper more efficiently - at the cost of using magnets more expensive than copper?

If you just want all the copper to be producing current constantly, then you would use a copper sheet, and have a N pole on one rotor, and a S pole on the other.  Your copper would flow current continuously - your problem is solved.  However, this creates a new problem.  The current would all be in the form of an eddy current which would produce nothing except heat.

If the only thing you change is the number of magnet poles, then the only real change you will see is a doubling of the Hertz frequency.  The alternating current will change directions at a faster rate.

Your diagram also needs improved.  As shown, portions of 3 magnets will be under one single coil at times during the rotation.  This will cause cancellation, and the coil will not produce anything (except heat) when this occurs.  

Ideally in a perfect world, you want a maximum and minimum of 2 magnet poles under a coil at any given time - never more and never less.  Unfortunately, we are not perfect and we do not build perfect alternators - we build decent alternators that work.

The stator thickness, prop size, wire size, etc determines how thick of magnets you need to use.  0.125 thick magnets will work with a thin stator, and small diameter prop.  Your goal should be to have all the components match in harmony with each other.

Take my thoughts with a grain of salt.  I'm not an electrical guru, and I don't play one on tv.

[windstuffnow]

  It seems to me you would be much farther ahead using a 24/18 layout if your going to use 24 magnets.  I really don't see an advantage of using the 24/9 unless your using small magnets and need the extra "real estate" for the wire to keep the coils thin.  

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[Spdlmt150]

"If the only thing you change is the number of magnet poles, then the only real change you will see is a doubling of the Hertz frequency.  The alternating current will change directions at a faster rate."

It would double the cycle, as well as cut the out of field copper in half by narrowing the windings. I'm curious if the reduction in resistance in the circuit would gain anything.

"As shown, portions of 3 magnets will be under one single coil at times during the rotation.  This will cause cancellation, and the coil will not produce anything (except heat) when this occurs."

The pic is a bit busy.... but it is nothing less than the usual 3 phase used on many machines, with a doubling of the poles. Only 2 poles under a coil at a time. I don't see that any cancellation would occur. You still end up with a N under one leg and a S under another. The difference would be doubling the pole reversal, and reducing the resistance of the out of field windings. Not sure if there would be any gain by doing so. Just wondering.

As of yet, I haven't built anything. I am just throwing ideas out. I know the principles (at least some of them) on which this works. I am just toying with ideas before I start making actual parts.

I am brainstorming for a machine with a max of 8 ft prop. I would like to get as much out of it as possible. I am willing to try something new if the general consensus is that it would be worth the effort. Unless I throw the ideas out here, I'll never know. I can model anything on screen, but I don't have the real world experience. My thought was that resistance reduces output considerably, and if the coils are narrowed it will reduce resistance possibly resulting in a more efficient alt.

Don't take this as a slam... I am coming from a good background with little experience in power generation. I'm still taking stabs. Might come up with the "next revelation" or might build Hugh's 4 footer. Time will tell.

Copper plate is ruled out from the start.... But what about ribbon? Take a .375 X .01 copper ribbon... wind it into a coil.... what benefits would there be? What drawbacks? I've seen the square winding wire - provides an almost solid coil.... What if ribbon was used to wind? No eddy's. Thickness maintained from the start. maximum amount of copper in the alotted space.

I always question why. Sometimes it leads to something. Sometimes it puts me in my place.

[Spdlmt150]

My thought was to keep the coils narrow. Less resistance. More copper generating current. Might be a plus. Might be a waste of time.

[hvirtane]

Would this effectively decrease the amount

of copper not producing current?

I think that you are right.

But on the other hand then there would

be more wasted space without copper at all?

I don't know yet how to make the calculations

if you would gain more than lose...

- Hannu

[dinges]

I'm not a guru.

But I think all you will achieve is lowering your cut-in RPM by 1/2. I.e. when with 12 magnets it would cut-in at 200RPM, it will now cut-in at 100RPM.

Whether power increases (all other things being equal) I'm not sure of. I think it would. Whether it's 2x as much? Doubtful. I think you get more output (W) by not only using more magnets but also doubling the amount of coils.

Or, you could reduce nr. of turns per coil by 1/2 to get the cut-in voltage at say 200RPM. That way, you could use the extra space for thicker wire with less resistance.

Interesting question, and one that I think can only be answered by either 1) building an accurate mathematical model of the genny or 2) building the actual genny.

[coldspot]

Unconventional thinking-

OK

Here goes

"If you just want all the copper to be producing current constantly, then you would use a copper sheet, and have a N pole on one rotor, and a S pole on the other.  Your copper would flow current continuously - your problem is solved.  However, this creates a new problem.  The current would all be in the form of an eddy current which would produce nothing except heat."

So if ya wanted to just maybe heat some water instead of a plate of copper and had a spiral of tubes instead between a dual rotor. The magnet placement would be all N one side and all S on the other???

Or normal N,S,N,S  on each

[dinges]

Suppose one plate was full of N poles and the other was full of S poles; what would 'change' or 'move' as the rotor was rotating? Would it be any different from when such a rotor would be standing still?

Answer: nothing would move. Nothing would change. Whether the rotor would rotate or stand still wouldn't make any difference to the copper plate/stator. Since a non-rotating rotor doesn't generate electricity or heat, it follows logically that in the case of that N & S rotor rotating, no energy would be delivered as heat or electricity.

So, you'd still need a conventional rotor with alternating N & S poles on each rotor plate.

[dinges]

More accurately phrased: There is little to none flux change as the rotor would rotate.

No flux change equals no energy being generated.

[finnsawyer]

You don't completely specify the problem.  Do you keep the same spacing between the magnets?  How much does the rotor size increase?  Not knowing these things, I'll put my own spin on it.  Keep the same coils and the same amount of copper.  What you have done is created spaces between the coils.  This requires a doubling of the rotor diameter, but the physical relationship between the phases and the magnets remains the same.  With twice the magnets it means only half the magnets are contributing to output at any given time, since the coils can only cover the same amount of magnet as before.  The magnets move faster past the coils, however, which will result in a larger voltage.  So, you have doubled your voltage at the added cost of twice as many magnets with the same amount of copper (and the same resistance).  If instead you invest nearly the same amount of money in magnets having twice the width (and area) and in coils having twice the amount of copper, but the same number of windings, you can use the same larger rotor with a heavier wire and get four times the voltage with the same resistance.  This happens because you have doubled the flux (larger magnets) and have doubled the speed at which the magnets move past the coils.  You have increased the average length per turn by 1.414 times the value before, but with twice the amount of copper you can use wire 1.414 times the cross sectional area giving the same resistance.  If this is confusing I discussed the same issue in a recent comment where in that case the magnet area and amount of copper increased by a factor of four with a doubling of rotor size.  That may be easier to follow.  I really don't see the emphasis that we getting lately on copper, since the real big cost is the magnets.  Nor do I see why people are worried by the amount of copper on the ends.  There seems to be an attitude that the ends do not contribute to the output voltage.  This is not exactly true as you must have a loop to get output voltage, and any design you come up with can be scaled up or down such that the resistance of the coils does not change with magnet size even though the amount of copper does.

If in a 3:4 alternator design you decrease the coil size to get less resistance, you would also decrease the rotor size to keep the coils touching.  Both of these effects act to decrease the output voltage.  Your adding magnets is an attempt to overcome this by increasing the rotor size, but at great cost.  A better solution would be to use somewhat larger magnets with lower resistance coils to start with.  

[hvirtane]

I think that the main point is to make the coils

more narrow. And that is a good idea?

Because then there is more copper in the right direction and less copper in the wrong direction.

- Hannu