The Wind is Free!

Ok, interesting. Why have you changed the magnet shape? Here is what I would have thought is the configuration to model (shown at point of peak voltage for that coil leg).

... the single strength. That also applies to the return field outwards from the centre line. I can't be too certain, but I don't think it will make much of a difference. Perhaps this picture may be helpfull. http://users.iafrica.com/c/co/cordewit/ME/hemi.gif

Aha, thanks, I can picture it now - its looking axially towards the centre of rotation. The peak power would occur when the magnet is directly over one of the legs. As shown, that looks like it is at the 'zero power' point, where it is not generating anything (zero crossing ...

... layers and the "outer" layers of the same coil, showing how different these layers capture the field. The steelplate? All ... the outer return lines closer to the magnet. I wouldn't know by how much, but it would certainly exasperate the effect. Coils that are much bigger ...

Great, thanks for interesting diagram. I am a bit confused however... :wtf: I can't quite picture it. It looks like one set of magnets and two coils? I (and most others) use one set of coils between two magnets. Two magnets (poles on broadest faces) would cause a very different looking field surely?...

There is another aspect about these coils that puts a limit to their overall size. The problem is that if the outer windings of the coil is much bigger than the magnet, they'll start picking-up return field lines which affect the flux density, and which lowers the expected coil response. Even ...

... of magnet grade/Br? And size of the magnet. The smaller magnets are strong close-up, but fade faster on distance. (So, the mid point will be much lower.) PS: I understand what you are trying to do, and I support it. Simplicity is the hallmark of the master. Its just that this business can ...

Thanks. From what I can see the figure you get from that formula for average strength will be a linear function of magnet grade/Br?

What I am after is the simplest possible, zero based measure of magnet effectiveness, even if it an approximation.

OK, This is what I was referring to: http://users.iafrica.com/c/co/cordewit/ME/Coil_xcut.bmp It's about two magnets flying past a coil, each at a 2mm distance. The fieldstrength inside the coil is the combination of the fields of each magnet (the red and the bue lines), and indicated...

Sorry,
I meant "formula": average fieldstrength = (2xG(2)+8xG(mid)+2xG(end))/6
You still need to work-out the G(2) and the G(end) to work out that average.

Which value is that?

No,
You're using a parameter that only partially contributes to the coil response, hence you're own observation of a decreased correlation. The value I gave you is directly (and solely) responsible for the coil voltage, so the correlation should improve.

Thanks... but isnt that stil linear? I am looking for a correlation remember, not a calculation to give a result in certain units.

. . .So I then used the link you posted, and calculated the gauss at a point in the middle of the stator. I got even less of a correlation! Maybe using grade directly is not so bad after all... You can't use that value on its own :!: Say you fly past the coils at 2mm distance.Then you need to know ...

I used Gauss instead if grade (from http://www.magnetichold.net/rarearth.htm), and interestingly got slightly less of a linear correlation. So I then used the link you posted, and calculated the gauss at a point in the middle of the stator. I got even less of a correlation! Maybe using grade directl...

And I have a link for you:
http://www.arnoldmagnetics.com/mtc/calc_gauss_rect.htm
I've checked it out . . . it works

Found this link you might find useful: http://s4wsbox.com/?q=node/3

Thanks windgat. You'll have to talk me through this slowly sometime. I didn't have much sleep last night. Can't stand it if I have to accept a "cop-out" solution because I can't find another way out. That's a bit of an insult to my intelligence. Anyway, ...

Ok! I will model some blades for you based on that. Have you factored in power loss in the pulley? And did you do an analysis of 3 vs 1 phase? Or even 5 phase? I take it all yr coils in this design are in series? Here is a very rushed calculation for your blades. ...

Disagree, I'd have more time to drink, or perhaps this is God's way of keeping me sober :?: Anyway, I've tried and turned this design inside out, but no way I can get this to work. I can make the coils bigger, but as soon as they get more than two or three times the size of the magnet, you pick up a...

Can you imagine how boring it would be if we got everything right first time?

Thanks for the offer. I'll need it.

Got a bit paranoid, so I checked the whole spreadsheet again, and . . . . found another blabs. Resistance calculation was wrong
That and the previous error threw the whole design out the window. (I'm getting old )

I will help you with the blade profiles... once I know RPM wind speed and desired kW. If you can estimate generator efficiency that would also be helpful. When you are ready , post that (under the Blades section) and I will give you chord sizes and twist angles.

... applying brakes @ windspeeds > 10m/s. You see, I don't need 2kW of power to maintain the geyser's temperture. That's for heating the thing up ... the heater element. I have thought about transformers, but I don't know how they will function at frequencies of 20 Hertz and below. They might just ...

I think you are aiming at a very high voltage... Other approaches may be to use a transformer, or even thinner wire, or maybe multiple stators/rotors. In a 10m/s wind, your actual tip speed would be 60m/s. In a gust of 15m/s, that's 90m/s. Would your blade material handle that? Or would the generato...