New Method Based on Shell Elements for Fast Calculation of the Stator Eigenfrequencies and Vibrations in Hydro Generators

The calculation of magnetically induced vibrations in the stator of an electric machine involves, on the one hand, the determination of the magnetic forces originating from the air gap field and, on the other hand, the calculation of the mechanical eigenmodes and eigenfrequencies. This work presents a new method for the mechanical modelling of the stator using shell elements in 3D, as an extension of a recently published method using beam elements in 2D. It is applied to the case of a hydro generator with a complex mechanical construction, including the frame, and the results are validated by measurements performed on a
$55\,\text {MVA}$
machine. It is shown that the developed method allows a time-efficient calculation of the eigenmodes and eigenfrequencies, providing an advantageous alternative to the classical analytical and finite element (FE) methods typically used for this purpose. This outcome is particularly relevant and applicable to the design and optimisation of large electric machines, as well as troubleshooting vibration problems in existing machines.