CT: Every wind turbine design has a cut-in wind speed, a rated wind speed, and a cut-out wind speed. At the cut-in wind speed, the blades start to turn and a trickle of electricity starts to be produced. Around cut-in, the generator may be used as a motor to help the wind overcome inertia and start the blades turning. The cut-in speed is typically 7 to 9 mph. At the rated wind speed, the turbine is able to generate electricity at its maximum, or rated, capacity. The rated speed is usually in the range of 25 to 35 mph. At the cut-out wind speed, the turbine shuts down to avoid damage. The pitch controllers feather the blades to let the wind flow past them and the rotor hub is braked. The wind usually has to return to a much lower speed, called the cut-back-in wind speed, for a certain amount of time before the turbine will restart. The cut-out speed is generally around 55 mph. The cut-back-in speed is around 45 mph.
S: NWW – https://www.wind-watch.org/faq-technology.php (last access: 9 December 2014)
N: 1. wind (n): “air in motion,” Old English wind “wind,” from Proto-Germanic *windaz (cognates: Old Saxon, Old Frisian, Middle Dutch, Dutch wind, Old Norse vindr, Old High German wind, German Wind, Gothic winds), from PIE we-nt-o- “blowing,” from root we– “to blow”.
speed (n): Meaning “rapidity of movement, quickness, swiftness” emerged in late Old English (at first usually adverbially, in dative plural, as in spedum feran). Meaning “rate of motion or progress” (whether fast or slow) is from c.1200. Meaning “gear of a machine” is attested from 1866.
2. The wind speed referred to a specific blade-tip velocity in the case of a specific turbine, at which the wind turbine starts supplying useful output power at the shaft.
S: 1. OED – http://www.etymonline.com/index.php?allowed_in_frame=0&search=wind&searchmode=none (last access: 7 December 2014)
http://www.etymonline.com/index.php?allowed_in_frame=0&search=speed&searchmode=none (last access: 7 December 2014). 2. EnEU – https://www.energy.eu/dictionary/data/392.html (last access: 9 December 2014).