A wind turbine has to match the power in the wind to the load on the alternator for it to work properly.
For every wind speed there is a certain maximum power available to drive the alternator and this means keeping the tsr of the blades near constant.
If the alternator doesn't develop enough power the blades run too fast and you fall off the peak of the curve. Similarly if the alternator is too powerful you stall the blades.
Part of the design is to try to get the load to match the power available in the wind.
Any losses in the system such as cable loss are part of this balancing act and certainly with the home built axial machines this line loss is fairly critical.
I wouldn't have expected this to be such an issue with a Bergey as long as the cable was adequate, too thin a cable would let the blades want to run too fast. I am a little surprised that it is possible to go the other way and stall the blades with a machine built down to a price, where the alternator cost would already have been cut fairly fine, but if they say so then I would accept it ( at least for a try).
Certainly this resistance you need to add will be quite small and probably adding a few yards of thinner cable would be the easier option than buying a costly and not easily changed resistor.
Try adding a few yards of light cable ( but heavy enough to carry the full load current without overheating). Then add some more until you see things reaching a peak then going the other way. You will find that you can easily add to much so I don't expect you will need a lot to prove the point.
Hope this helps, let us know the outcome .
Flux
