The stator roundness deviation in a hydro-generator can lead to spatially irregular distribution of air gap reluctance

resulting in asymmetry degradation in the main magnetic field. This asymmetry is a significant contributor to rotor unbalanced stress and core scraping. Firstly

according to the characteristics of stator roundness deviation

the expression for the magnetic flux density in the air gap of the generator is derived

revealing the space-time characteristics of the magnetic flux in various components of the asymmetric magnetic field. It is demonstrated that the stator roundness deviations can cause distorted magnetic flux linking with the shaft

and a qualitative relationship is established between the distorted magnetic flux and the harmonic components of the shaft voltage. Secondly

using a 334 MVA hydro-generator as an example

the magnetic field distributions under various stator out-of-roundness deformations are simulated

and the relationship between the stator roundness deviation asymmetric permeance and the shaft voltage harmonics is examined. Finally

simulation experiments on stator roundness deviation are conducted using a salient pole synchronous generator

and the variation characteristics of the shaft voltage are obtained. Simulation and experimental results show that the shaft voltage signal’s time-domain waveform and spectral harmonic characteristics effectively reflect stator roundness severity. This study validates shaft voltage can serve as a reliable diagnostic indicator for the magnitude of stator roundness deviation

introducing a novel detection method for stator roundness assessment in hydro-generators.