The raw output of most small wind turbines is 'wild' 3-phase AC. It's called 'wild' because it varies in voltage and frequency with the shaft speed (and therefore the wind speed), and it's not useful for much of anything in this form.
The normal method used for conversion to 12-24-48VDC for charging a battery bank is to run it through an array of bridge rectifiers. High-power 3-phase bridge rectifiers are available, but are extremely expensive. It's much more cost-effective to use standard 35-amp bridge rectifiers, which cost under $6 each. We sell them from our shopping cart HERE, item#2100.
This picture shows our "DanCAD" schematic drawing of a rectifier block. Yes, there is one half of one rectifier that's not being used....it's still cheaper than buying a 3-phase rectifier.
The rectifiers MUST be mounted to a heat sink and greased with heat sink compound, or they will not be able to carry their rated load. If you will be approching the limit of their current-handling capacity (usually 35 amps), you can parallel the rectifiers for each phase to double the capacity. Be sure to increase the size of the heat sink accordingly.
If you measure output after connecting the recitifer block to your wind turbine, you'll see that the voltage still varies. That's because the battery bank handles the voltage control on its own, with no circuitry needed, UNTIL it's full. That issue is addressed in another FAQ here.
http://www.fieldlines.com/story/2003/11/4/124345/260
