bigger lenz 2, alternator design

[filipeandremail]

Hi,

I'm back with the idea of building a VAWT. I want to build the one designed by ed lenz from windstuffnow but I want to build it a litle bigger. For example 4,92 x 8,20 feet tall (1,5 x 2,5 meters). The is just an example. the size can change, I just want it approximetly with that area.

My problem is to understand how to build a good alternator for it.

How can I know how many magnets, its size, the rotor diameter, the number of coils, wire diameter, number of turns, shape of the coil in order to build an alternator suitable to the turbine size?

The best price I found for the magnets in EU are the ones beeing sold in  http://www.solbergavind.se/ (sweden) or the pack of Grade N40 46 x 30 x 10 Phosphate Coating from http://www.cermag.co.uk/magnet_online_shop/old_online_shop/Buy_Neodymium_Magnets_Online.htm (UK). Unless anyone knows other place to buy cheap magnets in Europe the alternator should be designed with one of those kind of magnets.

Best regards to all.

[KilroyOdin]

Hi,a 3 phase alternator is a good start.  Typically 9 coils with 12 pole magnet sets. You can increase your coil count by multiplies 3 then use a ratio to solve for magnet pole sets, like 12 coils and 16 pole magnet sets.  Smaller diameter wire will allow more turns when making the coils giving more voltage but limit's the current. Larger diameter wire will give more current but limit's the amount of turns for the voltage, it is a trade off. When making your coils the center hole should be a few millimeters larger then the size of your magnets.

http://www.6pie.com/faradayslaw.php

has a lot of good info and do a search of this site for more good info.

Best of luck and hope to see some photos of your project.

Live in the present and plan for the future.

[Ungrounded Lightning Rod]

A thing to remember is that VAWTs (except for the likes of the Darrieus) run at a much lower TSR than HAWTs.  Savonius designs run under load at something like 0.8, while a typical HAWT runs at something in the range of 6 or so.  (Not sure where the Lenz ends up but I'd bet it's close to the Savonius.)

This will impact your alternator design.

If you get your cross section by going with a tall, narrow design you might end up with about the same RPM as a HAWT and be able to use the same alternator designs.  If you're closer to a square cross-section you'll have to accept the lower RPM and design for it.

That means a larger radius for the alternator, and perhaps more magnets and copper, to get adequate performance without a speed-increasing transmission.

Fortunately, with a VAWT an axial-flux genny is edge-on to the wind and isn't an obstruction to it.  So it can be made with a radius up to the width of the swept area without affecting the mill's wind performance or footprint.

[Ungrounded Lightning Rod]

"So it can be made with a radius up to the width of the swept area ...

Diameter.  B-(