Determination of the Equivalent Mechanical Properties of the Stator Core for Vibration Analysis in Hydro Generators

A crucial task for the assessment of magnetically induced vibrations in electrical machines is the determination of the eigenmodes and eigenfrequencies of the stator. The mechanical model for this purpose is usually based on the assumption of equivalent material properties to homogenize the laminated stator core. However, there are few references available in the literature on the appropriate equivalent parameters in the specific case of hydro generators. The objective of this paper is to determine the necessary equivalent parameters to represent the mechanical properties of the stator core of hydro generators under different temperatures and clamping pressures. This is achieved by developing a prototype of a stator core sector, on which several experimental modal analyses are performed under laboratory conditions. The experimental data are used to calibrate a calculation model, providing the equivalent material parameters which best fit the measurements. The main findings of this work are the empirical values of the Young's and shear moduli involving the component perpendicular to the laminations' plane, as well as their dependence on the temperature and clamping pressure. The results can be employed as inputs to the mechanical model of the complete machine in future works.