Analytical modeling of hydro-generators incorporating pole-slot effects under rotor out-of-roundness fault conditions

In response to the structural characteristics of hydro-generators, such as multiple pole-slots and salient rotor poles, and their differences between healthy and rotor out-of-roundness fault conditions, this paper proposes an analytical modeling method that considers pole-slot coupling effects under rotor out-of-roundness fault conditions. First, the independent influences of stator slots and rotor salient poles on the air-gap length distribution are solved separately. The influence of the stator slots is subdivided into contributions from the slot openings and the teeth, while the effect of the rotor salient poles is derived based on geometric structure. This establishes an analytical magnetic field model for the healthy state that accounts for pole-slot coupling. Building upon this foundation, the impact of the rotor out-of-roundness fault on the air-gap length is incorporated to further construct an analytical magnetic field model for the faulty state. A comparison of key electromagnetic performance parameters calculated by the model, such as air-gap flux density, electromagnetic force, back electromotive force (back-EMF), and torque, with finite element analysis results demonstrates close agreement. This outcome validates both the feasibility and the accuracy of the proposed analytical modeling method.