Effect of Saturation on Rotational Flux Distribution in Hydro Generators

Uprating of hydro generators requires studies to determine the potential areas of failure like hotspots in the machine core. Rotational core losses cause localized heating of the core; therefore, understanding the distribution and behavior of rotational flux in the machine is the key. This paper studies the distribution of rotational flux in a hydro generator as the core material is saturated. The percentage of rotational flux in the stator increases as the material is saturated, especially for aspect ratios above 0.6. This affects the loss distribution and total losses in the machine. Core losses at no load and full load are also computed considering the change in flux distribution, and an increase of over 50% in the total stator core losses is calculated. Moreover, experimental core loss data of nonsinusoidal flux densities in various parts of the machine at no load and full load operation are also presented.