Bens axial alternator complete - almost..

[gotwind2]

Just finished the DIY Alternator described in the topic below.

http://www.fieldlines.com/story/2009/2/14/17541/4546

My first attempt of a slightly new design (square rotors and a bicycle hub) is satisfactory, this is a dual rotor design.

with a huge 'air gap' - 14mm, using 4mm MDF as the stator coil 'carrier'.

3 amps @ 12v has been achieved, so only 36 watts of power, maybe more in a big wind.

Resistance of the coils is the killer, as commented by forum members Capt hook and Flux.

Each coil is 200 turns of (0.75mm) wire, 1.2 ohms per coil, 2 coils per phase.

I was happy with the bicycle bearing performance, but it leaves very little room for mounting it onto the wind turbine chasis.

A video here showing how easy it spins, cut in 12v @ 375 rpm.

http://www.youtube.com/watch?v=wMzVV-xVa8o

It is mounted verticaly at the moment, it will be mounted horizontaly with a set of 3 Ft diameter aluminium Terry blades (TLG).

I was considering casting the stator, but probably won't with the performance I am seeing at the moment, I will probably move on to a larger alternator design.

I've learnt a lot from this one though.

Thanks everyone for the great guidance - invalluable :-)

Ben.

[CmeBREW]

Good going Ben.

    Even as is, looks like that will make a decent little 3' diam charger on gloomy days for a small system.  I wonder if the stator had been thinner, say 1/4" thick, you could've used less turns of the same gauge wire, and reduced resistance some, had the same cut-in (Closer mag to mag gap and stronger flux)  and thus got some more power??  Difficult to know.

Look forward to your Watt results with those fast 3' diameter Terry blades (TLG).  

[gotwind2]

Thanks for the reply CmeBREW.

I think the massive air gap that the 4mm wooden (MDF) mount gives is a valid experimentation to the possible results of coil numbers, winds per coil and  configuration that can be obtained without such a permenant method of casting the stator. (Copper wire costs a lot of money as we know).

I could quite easily remove the 'hot glued' temporary coils from the wooden carrier and cast in resin, I may gain a reduction of 2-3 mm in doing so.

I wonder, if there is a calculation for the flux density for a given magnet arrangment over air gap distance - I suspect 2mm may make only a tiny difference.

Ben.

[kihon]

Hi Ben,

If you dont mind me asking, what are the magnets you are using, and how much did they cost? (also where did you get them from?)

At the moment, the biggest cost for my experiments are magnets

thanks

Kihon