Structural Dynamic Behavior of Wind Turbines - Wind Turbine Technology: Fundamental Concepts of Wind Turbine Engineering - page 641

Figure 11-9. Campbell diagram of the Sandia/DOE 2-m VAWT, presenting both theo-
retical and experimental modal frequencies vs . rotor speed. [Carne et al. 1982]
Instrumentation
The general layout of instrumentation on the test VAWT is illustrated in Figure 11-7.
For non-rotating tests, the turbine was instrumented with 18 piezoelectric accelerometers
on the blades, 10 on the central column, 20 on the supporting pedestal, and 6 on the turbine
shaft assembly. All input and response signals were low-passed at 100 Hz, amplified as
necessary with signal-conditioning amplifiers, and recorded. In the rotating modal test the
high, steady centrifugal accelerations prevented the use of accelerometers except on the cen-
tral column. Strain gages are normally installed on newly-designed wind turbines undergoing
development tests, and these gages are commonly used as response transducers for modal
tests as well.