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Ta Na
State Key Laboratory of
Vibration,
Shock and Noise,
Shanghai Jiaotong Univernty,
Shanghai 200030, China
Qiu Jiajun
Cai Ganhua
School of Mechanical Engineering,
Tianjin University,
Tianjin 300072, China |
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ZERO MODE NATURAL FREQUENCY
AND NONLINEAR VIBRATION OF
COUPLED LATERAL AND TORSION
OF A LARGE TURBINE GENERATOR*
Abstract: Zero mode natural frequency (ZMNF) is found during experiments. The ZMNF and vibrations resulted by it are studied. First, calculating method of the ZMNF excited by electromagnetic in vibrational system of coupled mechanics and electrics are given from the view of magnetic energy. Laws that the ZMNF varies with active power and exciting current are obtained and are verified by experiments. Then, coupled lateral and torsional vibration of rotor shaft system is studied by consid-ering rest eccentricity, rotating eccentricity and swing eccentricity. Using Largrange-Maxwell equation when three phases are asymmetric derives differential equation of the coupled vibration. With energy method of nonlinear vibration, amplitude-frequency characteristics of resonance are studied when rotating speed of rotor equals to ZMNF. The results show that ZMNF will occur in turbine generators by the action of electromagnetic. Because ZMNF varies with electromagnetic parameters, resonance can occur when exciting frequency of the rotor speed is fixed whereas exciting current change. And also find that a generator is in the state of large amplitude in rated exciting current.
Key words:
Zero mode natural frequency Coupled
vibration of lateral and torsion Eccentricity Rotor shaft Hydro turbine generator
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