# Voltage Output from 12VDC rated 500w Wind Turbine

Registered Users Posts: 2
So, a friend gave me a small 500w wind turbine outputting AC. I bought a small 3 phase AC to DC rectifier and hooked it up. Before I put the turbine on a pole I thought I’d test the output so I took the 3 blades off and hooked up my DeWalt drill to the shaft and spun it up. Yikes, the rectifier starts out with a very low DC voltage but as I spin the thing up the DC voltage ramps up to 40/50 VDC. The turbine label says it’s rated for 12VDC systems so why is it cranking out way way more than that? I’ve read other posts that imply the rectifier needs to be connected to a 12VDC battery so they turbine will “tie” to that voltage range. Is that correct? Or is the turbine out of control. I really don’t want to fry my battery bank by hooking this thing up! FYI, I do already have a dump load controller connected to my battery back (Morningstar TriStar TS-60) so that will make sure the bank doesn’t overcharge. Thanks in advance...

The open circuit voltage of an alternator is proportional to RPM (among other stuff).

So, what you are seeing is normal (voltage going upwards of 50 VAC or more).

The battery bank is what actually "sets the DC Battery Bus" voltage. And the current absorbed by the battery bank, DC loads, and dump loads is what makes the alternator have "torque" or resistance to turning (wind speed, amount of current flow, etc. determine the RPM of the turbine at any point in time).

With the turbine connected to your battery bank, it will get up to something like 13-15 VDC or so, and start charging the battery bank (winds something like 7-10 MPH typical minimum wind speed to begin charging). At (typically) 25-30 MPH or so, the turbine will be outputting its maximum charging current (at still something like 13=15 VDC battery bus voltage).

If you run a horizontal axis wind turbine without any electrical loads (no battery bank, no resistors, windings NOT shorted out), there is very little resistance to turning and the HAWT can over speed and self destruct in even "normal winds".

So, never let the turbine spin in good wind without DC loads and/or the ability to furl the turbine (turn out of wind, feather blades, mechanial brake, etc.).

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users Posts: 2
Awesome. Thank you for the reply...it helps a lot..