Apparent wind in knots and degrees. Note that a number of additional factors come into play when converting the measurements from the masthead anemometer into the true wind if a high degree of accuracy is required, including the following: In the presence of a current, the true wind is considered to be that measured on the craft drifting with the water over the bottom, and wind with respect to the sea bed as the "ground" or "geographical wind". The apparent wind on board (a boat) is often quoted as a speed measured by a masthead transducer containing an anemometer and wind vane
Variable speed wind turbine a Torque-rotor speed diagram, this looks as follows: where the black line represents the initial section of the operating strategy for a variable speed stall-regulated wind turbine. Ideally, we would want to stay on the maximum efficiency curve until rated power is hit. However, as the rotor speed increases, the noise levels increase. To counter this, the rotor speed is not allowed to increase above a certain value. This is illustrated in the figure below: Once the wind speed has reached a certain level, called rated wind speed, the turbine should not be able to produce any greater levels of