Opinion ID: 623909
Heading Depth: 1
Heading Rank: 2

Heading: variable speed wind turbines

Text: Electric power is generated from energy sources such as coal, natural gas, nuclear fission, flowing water, and wind, whereby the energy causes the rotation of magnets or electromagnets in association with coils of wire, producing an electric current. See the parties' joint tutorial of the technology presented to the ALJ, Hr'g Tr. Apr. 29, 2009. The electric current generated by wind turbines is usually fed to a centralized power grid, where electricity from various facilities is combined, stored, and distributed. Although wind is an advantageous source of energy, wind activity tends to be extremely irregular, whereas uniform electric current of fixed frequency is required to be fed to the power grid. This led to the development of variable speed wind turbines, which convert the irregular product of wind energy into the fixed-frequency alternating current (AC) required by the power grid. The General Electric '221 and '985 patents are directed to structure and circuitry that protect the turbine components from the effects of irregularities caused by emergency events such as lightning strikes, downed power lines, short circuits, and the like. The products whose importation is charged with violation of section 337 are variable speed wind turbines designated as Mitsubishi models MWT 92 and MWT 95. As products of the domestic industry, General Electric designated its models SLE, XLE, and SE. The Mitsubishi and General Electric turbines have the structure and circuit configuration called a doubly-fed induction generator, illustrated as follows: Gen. Elec. Br. 17 (from J.A. 2222). In operation, the wind turns the blades and causes the shaft to rotate, thereby spinning the rotor and producing a magnetic field in the winding coils, generating electric current. To produce AC electricity of uniform and fixed frequency, in doubly-fed induction generators a second magnetic field is imposed by current drawn from the grid and, by operations not here at issue, the system produces electricity of the desired uniform frequency. Testimony of Dr. Collins, Hr'g Tr. 46-48 (Apr. 29, 2009), J.A. 2746-48.