“Introduction:

The Vibration Institute’s commitment to the study of machinery began over four decades ago. Our founder, Michael Blake of Lovejoy, Inc., envisioned an organization where scientists, engineers, and other professionals from a broad cross-section of industries could come together to exchange information about measuring and analyzing machinery vibration.

The advantage in the PeakVue methodology over alternative methodologies for stress wave analysis is that the true peak g-levels are maintained in the wave form under all analysis conditions. The peak g-levels have proven to be useful in the important task of severity assessment following fault detection and identification. The fault severity chart recommended for reference is presented in Figure 1.

The wind turbine generators selected for analysis are 1.5 mw electrical generators supplying 60 Hz power to be placed on the grid. The primary equipment is placed in a Nacelle attached to the top of a tower (typically around 200 ft above ground level). The Nacelle is capable of being yawed to line up with wind direction. The primary equipment in the Nacelle is the nose section supporting three blades with controllable pitch, a pedestal bearing stand supporting the main shaft, a gearbox usually consisting of a planetary gear section followed by a spur or helical gear section. The spur or helical section of the gearbox consists of a double speed increaser (reduction). The planetary and spur (helical) gear sections are housed in a single housing making them very compact. The output of the gear box is directly coupled to a generator.

Other auxiliary equipment located in the Nacelle consists of the motor, controller and bearing for yaw action, motors, controllers and bearings in the nose section to control the pitch on the blades. Motor driven or direct drive oil pumps to provide proper lubrication to all moving parts. Of all the equipment located in the Nacelle, the gear box is the more complex for vibration analysis. This is due to the compactness and large speed variation from the input shaft (the carrier of the planetary section) to the output shaft from the spur or helical section which is directly coupled to the generator. An impacting level of 1 g in the input may represent a fault of concern (see Figure 1), whereas an impacting level of 1 g on the output of the gearbox would be of no or little concern.”