Bens new single rotor axial alternator

[Gotwind Ben]

Good news, I'm more than happy :D
Test are showing 200 watts @ 1275 rpm into a 12v battery. The polycarbonate sheet (virtually indestructable) is a nice feature if I say so myself - you can see whats happening :D
All achieved with a hacksaw and set of files (apart from the bearing housing).

[Gotwind Ben]

The most respected man I know on this subject replied (Flux on fieldlines).
I can't say enough good about this man and how he 'gives' for free to people like me and others, bit of an enigma. I believe an older man with massive experience.
His comment.
"The whole thing looks very inefficient, single rotors with no return flux path are poor at best. if you must do it that way then use thicker magnets and thinner coils so the return path is not within the coil. I suspect you could halve the thickness of your coils with little loss in voltage."

Flux.
http://fieldlines.com/board/index.php/t ... 997.0.html
I beg to differ, I'll keep going..

Hey Ben, had an idea. If, and it's a significant if, iron filings stirred into resin means that you end up with set epoxy with each filing grain isolated by a micron or two, you could have an electrically nonconductive but magnetically active plate to strap your coils to.
You'd get a return flux path without eddy currents, unless I've finally lost it.

[Gotwind Ben]

Good thinking Tim.
But I think it would still act as an eddy current 'brake' - not completely sure though :?:

I think it would be as easy to engineer in a second steel rotor plate on the back of the stator (without magnets) to focus the magnetic flux through the coils.

Nice work Ben, very nicely put together, looks great - much neater and more professional looking than anytihng I manage to cobble together :oops:

I would be tempted to try a smaller gauge wire with same number of turns for flatter coils. Are the coils getting hot?

200W is great, if a few refinements can boost the output some then you are certainly onto a winner.

What sort of output are you getting at lower rpms?

[Gotwind Ben]

Hi Microgreen.
It takes time and patience to get things looking reasonable, It's taken me a long time to realise this.
and about £100 to develop - not bad.
As far as performance is concerned, I'm pretty happy.
It would be suitable for a fast 2 or 3 blade 3 Ft diameter prop, wooden or aluminium.

Ben,

This is just a thought, have you considered using a smaller wire with more turns, making the coils much narrower and increasing the coil count? Treat EACH COIL as it's own "phase"? Yes, I know it would take a fair number of discrete diodes (Two per coil), but diodes are cheap. I am thinking of maybe 18 to 24 coils with 200+ turns each of #22 to #30 wire. All coils would be in parallel, so simply increase turns & decrease wire size until you get to the voltage you want, then increase coil count until you get to the amperage you want. You could test this with a single coil. 24 coils @ 0.7 Amp each @ 12V = 200W. Using this approach, you could also increase magnet count (in pairs) w/o regard to coil to magnet ratio.

My thinking is that in your very small form factor with your small magnets, you might improve efficiency even though it appears you are increasing your IR losses per coil. I am picturing "non-tapered" (straight) coils wound around 1/8in round stock at either end with an inside length of 2in and a total width of less than 1/2in.

I HAVE NOT done any calculations on this for physical feasibility, and obviously I have not tested the theory, it is just a thought....but I am curious :-) Maybe I will get a-round-to-it and give it a try :roll: Sigh, sadly,though, now I have to go to work :cry:

Fish

[Gotwind Ben]

I do like your thinking Fish.
I'm not sure how much you could gain however, be interesting to find out.
May I pass this task onto you, when the tiresome task of work permits, the weather is improving, time to tinker in the shed/shop. :D