A total of 14 variable-speed upwind wind turbines with pitch
regulation have been considered. The rated power per unit is
2000kW for a rotor speed of 14.5 rpm and a wind speed of 12 m/s.
The cut-in and cut-out wind speeds are 4 and 25 m/s, respectively.
Each turbine has three blades and a rotor diameter of 90 m. The
tower is made of steel and has a conical tubular style. All the wind
turbines incorporate the same 50 Hz four-pole generator, but the
three-stage planetary/helical gearboxes are supplied by different
manufacturers.
The wind turbines are built with a CM system that registers the
signal from an industrial accelerometer specially designed for
low-speed applications. It is mounted in the axial direction on the
gearbox casing between the intermediate and the high-speed
shafts (as shown in Fig. 1). Two analog inputs permit monitoring
of the output power and the generator’s speed of rotation at the
instant of the measurement.
The rms value of the vibration acceleration, อิอิ is calculated
from the frequency spectrum of the raw time signal over a frequency
range from 0 to 10 Hz as shown below: