Dynamic characteristics analysis of energy storage flywheel motor rotor with air-gap eccentricity fault

The air-gap eccentricity of motor rotor is a common fault of flywheel energy storage devices. Consequently, this paper takes a high-power energy storage flywheel rotor system as the research object, aiming to thoroughly study the flywheel rotor's dynamic response characteristics when the induction motor rotor has initial static eccentricity. Firstly, the formula of unbalanced magnetic pull (UMP) of the motor rotor based on the Timoshenko beam element is derived by the finite element method. Then, utilizing the beam element model, an electromechanical coupling dynamic model of the flywheel rotor incorporating UMP is established. At last, the effects of eccentric amount and direction on the steady and transient characteristics are calculated and analyzed. The accuracy of the theoretical results is verified by the flywheel vibration test. Based on our analysis, the following conclusions are drawn: eccentricity will change the shape and position of the displacement waveform and axis orbit. New frequency components related to the rotating magnetic field of the stator appear in the spectrum, and new resonance peaks appear in the acceleration response. When the eccentricity is doubled, the amplitude of double rotating magnetic field frequency increases approximately 8 to 10 times, and similarly, the amplitude of new resonance peaks increases approximately 6 to 10 times. These increases are positively correlated with the eccentricity, following a power function relationship. The variations in eccentric amount and direction will also lead to predictable alterations in the position of the axis orbit and the critical speed of the acceleration response. Notably, a novel aspect of our approach lies in considering beam deformation during the calculation of UMP. This enhancement ensures a more accurate and suitable modeling of eccentric beam elements.