Mini-modal testing of wind turbines using novel excitation
Modal testing of wind turbines can be fairly difficult because placing transducers on tall structures and providing low frequency excitation create problems. Moderate-size turbines are 100 to 200 feet tall, and their modal frequencies are very low, 0.1 to 5.0 Hz. In the mini-modal concept, only a limited number of response measurements are used in conjunction with a reasonably accurate finite element model to determine the modal parameters. Several techniques of low frequency excitation were explored, including impact, wind, step-relaxation, and human input. In tests using the mini-modal concept with human excitation, modal frequencies of large turbines have been determined in less than one day. As one application of these techniques, a prototype turbine was tested and two modal frequencies were found to be very close to integral multiples of the operating speed, which would cause a resonant condition. The design was modified to shift these frequencies, and the turbine was retested to confirm the expected changes in the modal frequencies.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (USA)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 6281253
- Report Number(s):
- SAND-84-0984C; CONF-840178-1; ON: DE85000666
- Resource Relation:
- Conference: 3. international modal analysis conference, Orlando, FL, USA, 28 Jan 1984; Other Information: Portions are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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