Abstract: The energy method in nonlinear vibration of elastic body is utilized to analyse the phenomena of bending-torsional vibration of the large hydrogenerator flexible shaft system excited by electromagnetic parameters. The study shows that bending vibration can excite torsional oscillation appearing. And that the two kinds of vibrations couple together complicatedly. The singularity theory is employed to investigate the bifurcation modes of resonance in physical parameter space to find the range of parameters for controlling resonance, which is of help for the hydrogenerator design and security operation. Under bending-torsion vibration case, the theoretically numerical results of bending vibration responses are approximate to the experimental ones.

Key words: Electromagnetic field, Hydrogenerator Energy method, Nonlinear Bending-torsion vibration Bifurcation