How many mags and coils for this?

[amiklic1]

How many coils and mags (2"x1"x0.5") to put on 90 cm (3') rotor? It's supposed to be 12V machine, and some 60W total at 10m/s wind.

Should I use smaller mags, maybe, so to decrease the torque needed to turn the rotor?

The speed should be the same as of 4' Hugh's design axial flux.

What to look for?

[dinges]

Hi,

I can't help you much except tell you what I've done;

It will be an .7m diameter turbine (genny is finished, props not). It needs 50RPM/V (33 RPM/V in star), double rotor design with 2*12 magnets of 19*13*6mm; roto diameter is 15 cm. 9 stator coils (3 in series per phase; 3phase) of 130 turns each. Cutin-RPM for 14V is about 700RPM (450 in star). Normal output would be about 10W, max. output 50W (limited by wire diameter; wiredia=0.65 mm)

You can look in my photo-uploads (or the thread of 'my projects so far') to see how I've done things.

Hope this is a bit of help.

Peter,

The Netherlands.

[Flux]

If you keep the 2 x 1 x 1/2 magnets single rotor you will need to have a fairly large air gap between the magnet rotor and stator to prevent stall.

You could use much smaller magnets and make it dual rotor. Unless you can make your own hub there is a limitation with the hole in the stator to take a standard trailer hub. Also with a standard hub the bearing friction will become significant and you may have to use a lower tsr than you would otherwise choose.  

To keep 3 phase you need 8 magnets per rotor and you could easily manage with 6" discs if you can cope with the problem of the stator bore. If stuck with a standard hub you may have to use bigger discs to keep the stator centre big enough.

8 pole dual rotor using magnets 3/4" square by 3/8" thick would be quite nice but much depends on the magnets you can get. Stick to 8 magnet 6 coil or use even smaller magnets and go for 12 magnet 9 coil as Peter suggests above.

I think Peter must have quite a thick stator to have that high a cut in speed, with a bit thinner stator to lower the cut in speed that size of magnet would be fine if you can get them.

Flux

[dinges]

Flux is right, my stator is very thick (11mm, plus 3mm total airgap). The magnets are only 6mm thick.... The newer cycle genny has much bigger magnets and more of them (16 instead of 12). The stator will be the same thickness though, but is 'relatively' thinner, when compared to the other dimensions of the small genny. Also, the holes in my coils are too small so I get cancellation. I've learned a lot from my genny, esp. on what I did wrong. Yet, it still generates pretty good :-), but it might have been better.

Peter,

The Netherlands.