hooking up a s.w. wind air 303 to an external rectifier

**ouzel** · August 8th, 2012, 9:55 PDT

i've got an old air 303 that seem to have a bad circuit board. i also have an external rectifier from missouri wind. is it possible to directly connect the turbines stator wires to the slip ring brushes, run the wild 3 phase ac the turbine produces down the tower, then through the remotely mounted rectifier to the battery bank? if so, which 3 of the 4 stator wires get hooked to the 3 slip ring brushes? i assume wire # 4 is a ground. what does this one get attached to?how do i tell which one is a ground?

**Cariboocoot** · August 8th, 2012, 10:05 PDT

Welcome to the forum.

You've got a problem. The three slip rings are designed to take DC: one for positive, one for negative, one for the ground.
When you have 3-phase AC output you need one slip ring per line and a fourth for ground. If you leave out one of the AC connects you leave out approximately 1/3 of the power. If you leave out the ground you leave the turbine open to picking up every bit of stray Voltage (lightning) around and sending it on down the wire.

You could use the slip rings for the AC and fabricate an external grounding brush, but it probably would not be too reliable. You could also install a physical stop on the turbine so it can't swing through 360 degrees and ground the head with a loop of wire. None of these solutions is very desirable. Maybe you can just get six rectifiers of appropriate size and wire up your own circuit, although the regulation would then be external. I'm not sure if the 303 is a PMA or has an active rotor winding. It makes a difference.

In any case, take it down to do any testing and modification/adaptation. You can control conditions on the ground by spinning it with a motor so you get consistent output. Then you'll see what (if any) power you can get from it with different configurations.

**ouzel** · August 8th, 2012, 17:26 PDT

thank you for the good info. 2/3rds of the power might not be so bad in this situation. we mainly rely on solar and wind just fills in the gaps. besides ,its either flat calm here or blowing gales. also no ground may not be so bad either. we live in south east alaska and in 20 years here i have only seen lightning twice and never close to home and the turbine is mostly discconected from the battery bank , only on when we are home and its windy.can you pick up stray voltage from anything else? any sure way to tell which wire is the ground ?according to the manual, the 303 has a pma. how does this affect what i'm trying to do. thanks again.

Originally Posted by Cariboocoot

Welcome to the forum.

You've got a problem. The three slip rings are designed to take DC: one for positive, one for negative, one for the ground.
When you have 3-phase AC output you need one slip ring per line and a fourth for ground. If you leave out one of the AC connects you leave out approximately 1/3 of the power. If you leave out the ground you leave the turbine open to picking up every bit of stray Voltage (lightning) around and sending it on down the wire.

You could use the slip rings for the AC and fabricate an external grounding brush, but it probably would not be too reliable. You could also install a physical stop on the turbine so it can't swing through 360 degrees and ground the head with a loop of wire. None of these solutions is very desirable. Maybe you can just get six rectifiers of appropriate size and wire up your own circuit, although the regulation would then be external. I'm not sure if the 303 is a PMA or has an active rotor winding. It makes a difference.

In any case, take it down to do any testing and modification/adaptation. You can control conditions on the ground by spinning it with a motor so you get consistent output. Then you'll see what (if any) power you can get from it with different configurations.

**Cariboocoot** · August 8th, 2012, 17:49 PDT

PMA: Permanent Magnet Alternator. Magnets spin inside field windings to generate power. That power has to be regulated 'externally'.
This is as opposed to an alternator with rotor (or armature) windings which have some of the power fed back there to create an electromagnet which is spun inside the field windings. That kind is often regulated internally by varying the amount of Voltage going to the rotor windings.

Attaching a basic 3-phase alternator diagram. Ignore the armature windings & slip rings for it.

In effect you take the negative and positive pulses off each winding junction and redirect them to the proper DC wire via the rectifiers. The way it was one of the pivot slip rings was for (+), another for (-) (from the rectifiers) and the third would connect the case of the turbine head to ground. This should be obvious in the wiring, but sometimes engineers don't do obvious; they may have taken the ground wire to the circuit board first instead of directly to the casing. The output wiring should also be obvious, depending on what was used to regulate the output. Normally you could expect it to be connected directly to the battery terminals with a diversion regulator on that to make sure battery Voltage did not climb to high (by shunting the excess Voltage to a dump load).

I'm not too keen on losing the grounding as the turbine itself could short out and energize the casing. Having that grounded keeps it safe, although it may cause some internal component to blow. Like the rectifiers perhaps? I'd check it very carefully before going any further.