multiple stator wind turbine alternator help

[whirligig]

Hi All, I'm new to the site, wish I'd found it years ago, seems to be a wealth of experienced people here.

I'm wondering if anyone here has experimented with a multiple stator alternator design like the one I'm building for a wind turbine.

So far, it's going to have three stators (with room for two more) and four rotors (each with twelve 1.5 dia X .375 thick neo magnets).

What I want to find out is if anyone has collected data regarding the amounts of magnetic material and its ratio to the mass of copper in the coils plus gauge and number of turns in the coil winding to produce a given amount of voltage and amperage.

I would like this turbine to produce a lot of voltage but no more than 440v at about 350rpm.

[shylo]

eddy

HI, Gig the layered style will just create more losses.
Check "Go Vertical" at Fieldlines.com
shylo

[Allcanadian]

Here is an axial flux generator calculator

excel tool for calculating axial flux generators

AC

[Allcanadian]

@Shylo

HI, Gig the layered style will just create more losses.
Check "Go Vertical" at Fieldlines.com
shylo

I'm not sure I would agree, I have read a large number of scientific studies stating that more layers is in fact more efficient than a single unit because both sides of the magnets actively induce the coils. They state power density and efficiency are greater because flux leakage and iron losses are reduced.

As well I can confirm this fact and found flux linking is very much greater in a small gap between magnets in a non-metallic disk versus using an iron backing. The coils should be kept as thin as possible and the gap small for maximum efficiency.

AC

[shylo]

yes

@ AC, but the design that Gig suggested is basically the same as " Go Verticals'.
I think the answer is in how to direct the magnetic field, but not cause the eddy currents. The opposite reaction that happens ,should be able to be controlled?
shylo

[wrtner]

So far, it's going to have three stators (with room for two more) and four rotors (each with twelve 1.5 dia X .375 thick neo magnets).

Don't forget that each magnet will induce a voltage in TWO coils, the
two either side of it. And so, the inner coils will be hit by two magnets
at once. You will need to ensure they don't cancel out, but this should
not be difficult.

[Allcanadian]

There are other things to consider as well, if we have 8 magnets and 8 coils and we double the disk diameter one would think we would get double the power. However the same magnets simply pass the same coils faster at any given RPM generating a higher voltage but now we have a space between each coil so average power does not change nearly as much as we would expect.

So we find things that are counter intuitive until we revert to fundamental physics...the basics. A magnetic field of magnitude X crosses Y Kg of copper wire in a coil. More X or more Y equals more power and the longer this happens the more energy has been transformed.

In fact I have learned more by going back to the basics and building upward than I ever have starting at the top. Generally speaking the beginning determines most of what happens after the fact. So trying to build a motor or generator without knowing why everything happens and for what reason is treacherous path at best.

AC

[AetherScientist]

What factors determines the overall output power?
I know, the speed and the strengh of the magnets. But What about the coils?
The bigger the better? and the AWG?

[wrtner]

What factors determines the overall output power?
I know, the speed and the strengh of the magnets. But What about the coils?
The bigger the better? and the AWG?

Wow! Is this a case for "dimensional analysis" ?

Output power (foot x pound per second) is proportional to:

wind speed (feet per second)
strength of magnets (gauss)
no. of coils
no of turns on each coil
permeability of core of coils (henries per foot)
air gap between coils (feet)

Any more ?
.

[AetherScientist]

Just one more...
What about the diameter of the cross section of the coil (awg)?
the bigger the higher output?

[Allcanadian]

Just one more...
What about the diameter of the cross section of the coil (awg)?
the bigger the higher output?

Think of it this way, it comes down to the change in the magnetic field density producing a force on the free electrons, more change=more force(EMF). So more copper=more free electrons=more current however the force(Emf or Voltage) per turn is small. Thus more turns equals more voltage because each turn is in series and we are left right back where we started with how many Kg of copper to produce X amount of Power(Volt/Amps).

When we speak of induction more turns=more volts because each turn is in series and bigger wire per turn=more current.

Concerning coils, the only part that matters is that under the influence of a changing magnetic field. Thus the top and bottom of the air core coil in an axial flux machine are not induced because they are not crossed by the field. The sides are crossed at 90 Degrees thus a maximum Emf is induced. We could have a coil 1 mile in diameter and it means nothing because the only part actively induced is that being crossed by the magnetic field. We may say "crossed" but we are speaking solely of a changing field density.

Now it gets interesting because an expanding or contracting field produces a force(Emf) just as a static field that is physically moving produces a force(Emf). If a field is expanding to the left at 1 m/s it is no different that a static field moving at 1 m/s to the left, the rate of change is identical. This is why we say it does not matter how the field change occurs... only that it does.

Generally speaking we want enough turns to generate the required voltage and heavy enough wire to generate the required current. RPM just means we induce the same coils more often, more voltage, more current and more power.

AC

[AetherScientist]

Thank you very much Allcanadian. Now I understand better how and why it works.

So I'm going to design one axial flux generator of 5 cm/1.95 inches of radius. 1 rotor, 2 stators.
As far I know the stator has to have 9 coils to get three phase output. So I think the same amount of magnets, 9, will be required. Those 9 coils are connected between them:

http://www.instructables.com/files/d...9XGO.LARGE.jpg

[AetherScientist]

I'm just designing in 3D program the pieces to do it very easy.
You can get 3d printed copies of these parts and then you buy the required coils and magnets to build it.

I'm thinking of buy these magnets, but they seem very cheap. Any experiences with these or similar magnets? I mean, I'm not fully convinced that magnets can be as cheap as these ones. Maybe they are of less strength?
5pcs 20mm x 2mm Disc RARE Earth Neodymium Super Strong Magnets N35 Craft Model | eBay

[citfta]

Magnets

Hi AetherScientist,

Here is a link to similar magnets that are about the same size but much stronger for about the same price. The similar size ones are near the middle of the page. Hope this helps.

Applied Magnets & WindMax Wind Turbines

Carroll

PS: I just tried that link from this post and sometimes it takes you to a sign in page. Just close it and try again. It should take you to a page that has a bunch of cylinder and disc magnets.

[whirligig]

Thanks for all the feedback. I've been working a little on a spreadsheet that is helping me collect some turbine generator/alternator data I was looking for.

Some of the columns are: swept area of blades, amount of magnetic material, weight of copper in coils.

I wish I'd gotten magnets twice as thick as did, still could but they are so expensive!

If anyone is willing, I would like more specs on other turbines and generators/alternators- swept area (or diameter), volume & grade of magnetic material, and mass of copper in the coils. I would also gladly collect data on gap widths and anything else you're willing to offer.

I'll be happy to share this collected data/spreadsheet with everyone as well.