Resonant frequency tuning of all critical elements is an actual engineering challenge in designing turbo generators. In particular, one of these elements is the stator core. First, the procedure involves assessment of the eigenfrequencies and amplitudes of vibrations of the element. The present study considers the well-known analytical approaches to the calculation of the vibrational eigenfrequencies of stator cores of turbo generators. In these approaches, a mathematical model of the core represents the dynamics of a ring in terms of rod theory. Consequently, it is possible to estimate the eigenfrequencies and vibrational modes correctly only in the case of the thin-walled core. Practically, however, the radial width of the outer side of the turbo generator’s stator core is comparable with its average radius, so the use of these models can result in unsatisfactory accuracy of calculations. In order to solve this problem, the present study provides an analytical method for the calculation of eigenfrequencies of the stator core. The method represents the core as a long thick-walled cylinder. The results of finite-element modeling of the core vibrations verify the accuracy of the calculation of eigenfrequencies. The study shows that the proposed method gives more accurate results than the formulas used in engineering practice.