There is no simple answer to this. What you are looking for probably doesn't exist.
The ideal thing would be a pm dc generator with cut in speed below 200 rpm amd a maximum output of at least 20A at something like 600 rpm.
In real life there are very few pm dc generators available and there would be no market for one of this spec except for wind power. You then have to look to motors, which are more readily available. Again very low speed 12v motors hardly exist ( nobody wants them). You are then forced to try and adapt some form of motor that someone makes for a need that exists.
Probably the most versatile things are servomotors, that are typically reasonably low voltage and can carry short time currents of many amps. New they cost the earth, but surplus they only have scrap value until somebody finds a market to satisfy fools building toy windmills.
The Amteks are basically the lowest grade of servomotor and if you find the right ones they do fairly well. They are all higher voltage and higher speed than the ideal device.
You have to realise that if something generates 150v at 2000rpm it will generate 15v at 200rpm. Even that is confused by the fact that the speed quoted will be under normal working conditions as a motor, not a generator.
You also have to realise that the current will be limited to the maximum current as a motor. If it can only handle 3A at 150v then it will only handle 3A at 15v so the power rating is reduced to 1/10. Most motors will take a fair overload short term and with the wind blowing on it you may be able to push that 3A motor to perhaps 10A for wind duty but the efficiency will be low and the long term survival may be limited.
Information quoted may be confusing if not actually wrong and the quoted data is not always sufficient to make an intelligent choice but given lots of experience you can sometimes make a reasonable guess. Don't forget you have to consider your prop size when selecting cut in speed and maximum current handling.
Best stick to things that have been tried and found to work, some Amteks are better suited than others ( look what others have used). Treadmill motors have been used with some success but there is a lot of junk available that will be of no real use and someone will try very hard to convince you it is perfect and try to charge 20 times scrap value for it.
You need also to use blades that have proved suitable for the type of motor, pvc blades need much slower motors than wooden ones or perhaps Jerry's blades.
The whole thing is a minefield of disasters waiting to happen. When you could get a surplus motor for scrap price there was little to loose but when I see some of the junk on ebay for more than a commercial wind turbine I say "buyer beware".
At best these little dc motor things are only going to supply modest loads in good wind areas. Don't expect much and don't pay much and you will not be disappointed but unless you can find a motor cheap it may be better to consider an alternator designed for wind power, they are not very cheap but may be better value for money than a useless dc motor at a scam price.
Flux
