Using car alternator rectifiers.

Bookmark

If you have an old car alternator sitting there doing nothing, you can use its rectifier for your windmill. These rectifiers are a 3 phase heavy duty unit, and designed to work under extream conditions.

The following is how to use a rectifier from a Fiat alternator. Why a Fiat, well they are a bit of a natural resource around here, the owner of the property I'm renting has a thing for them and there are hundreds of old Fiat cars here, seriously.

But the same princible applies to just about any alternator, they all look different and the rectifiers are all sorts of shapes and sizes, but they have in common...

3 input leads. 3 phase AC in.
2 output leads. DC out.

Le alternator, all the way from Italy. Undo the long screws that hold the thing together, dont worry about removing the pully. The pully end and armature will slide out, maybe with the help of a big hammer.
If you look into the depths you will see 3 thick wire from the stator connected to the rectifier.
Remove the rectifier from the case ( it may slide out from the back ). You will have to undo some screws and the output power terminal. Just keep unbolting stuff untill you can get it out. Cut or unsolder the 3 stator wires. These 3 terminals will be connected to the 3 phase output of our windmill.
If you look at this rectifier ( and just about all follow this same rule ) you will see two plates, each with 3 diodes connected. One of the plates is positive and the other is negative. The negative is the plate that was eathed to the alternator case, and the possitive is the plate that was insulated from the casing and connected to the output terminal. But if the alternator is from some weird european car that has a possitive earth, then everything I said above is reversed, I think.
Using 3 bridge rectifiers. Dick Smith sell a cheap 35amp bridge rectifier that can be used as a 3 phase rectifier. You need 3 bridges, and wire them as shown below. Be aware that sometimes these bridges are labled incorrectly, always use a multimeter to check the connections. The one shown here is correct, the + sysbol lines up with the tag at right angles to the others. I have seen some where the + and AC is printed on the other side.