Jim Thorn is correct in stating that the V80 wind turbine has a constant speed generator. The rotor turns at 15.5 rpm and the generator at 1,800 rpm if the turbine is producing 1 or 1,800 kilowatts.
He did, however, previously make the statement that “big commercial windmills (turbines) turn at only one of two speeds: Stopped or full-bore.” This is not accurate as “many” modern megawatt turbines (Siemens, GE, Clipper) use variable speed generators that turn at different speeds depending on the wind speed.
The Siemens 2.3 megawatt turbine has speeds of 7 rpm rotor/637 rpm generator at 1 kilowatt and 16 rpm rotor/1,456 rpm generator at 2,300 kilowatts.
A variable speed generator will produce power at different frequencies (measured in hertz) so it is necessary to have a frequency converter change the power to 60 Hz before connecting to the grid.
Having a constant speed generator (like the V80) does not mean that at 7 mph the wind turbine must consume power from the grid to keep turning. It is in fact the wind moving across the massive surface area of the aerodynamic blades that causes the turbine’s rotor to turn. At lower wind speeds the blades pitch toward an angle of 0 degrees which allows the blades to capture more wind. At higher wind speeds the blades will pitch toward 90 degrees (out of the wind) and this is how a wind turbine controls the speed of the rotor at variable wind speeds.
A wind turbine will never take power from the grid and use its generator as a motor to keep the rotor turning full-bore as Mr. Thorn states. His statement that “clearly, the power to keep the rotor turning must come off the grid” is his own assumption and not based on any manufacturers’ spec sheet.
The V80, like many wind turbines, utilizes an asynchronous generator. This means it requires a small amount of electricity (over a period of a few seconds) from the grid to create the initial electromagnetic field prior to generating power.
This is not unique to wind turbine generators as all forms of power generation (coal fired, natural gas, hydroelectric, etc.) utilizing asynchronous generators require that small amount of “excitation” current to produce power.
Don’t take my word for it, do some research and make your own conclusions!