These turbines provided insight for The Wind Turbine Company's turbine design efforts.
The Smith-Putnam Turbine
Cited as the world's first megawatt-size wind turbine, the Smith-Putnam turbine designed by Palmer Putnam was installed, grid-connected, and began operation in October 1941. This innovative 2-blade, downwind turbine featured individually hinged rotor blades and a 175 foot rotor diameter. The rotor blades were hydraulically pitched to regulate power, and a fluid coupling in the drive train permited the use of a synchronous generator. The turbine had a rated capacity of 1.25MW.
The turbine operated 1100 hours before a blade failure occurred. The onset of WWII prevented dedication of resources necessary to see this turbine into commercial reality. The Smith-Putnam machine was perhaps 50 years ahead of its time.
The MOD-1 Turbine
In 1979, GE installed the MOD-1, a 2 MW turbine developed under a U.S. DOE sponsored, NASA administered program. This was the first MW-size wind turbine sponsored by the U.S. Government. It was a 2-blade, downwind design with a 200 foot rotor diameter, full-span pitch control, and blades rigidly attached to the rotorshaft. It featured a synchronous generator using a dry slip clutch to accommodate wind gust induced torque spikes.
The turbine operated at least 18 months. Full operating history is not known. The MOD-1 highlighted the downwind turbine problem of impulsive noise created as the blades passed through the turbine tower shadow.
The WTS-3 & 4 wind turbines
The WTS-3 & 4 wind turbines were designed by Hamilton Standard a United Technologies company. The WTS-3 (3MW) was installed in Sweden in 1981. A 2-blade, downwind design with a 78 meter rotor, full span pitch control, a "teeter" hub rotor blade attachment, "free-yaw", a synchronous generator, and a "soft" tubular tower. The WTS-3, a first prototype, operated successfully for 11 years (55,000+ operating hours). It may still hold the record for most electricity produced by a wind turbine.
The shorter-lived WTS-4 (4MW) was installed in Wyoming in 1982 and accumulated 7,500 operating hours before a second accident destroyed the machine.