Loss Distribution in Stator End Region of Turbo-Generator During Asynchronous Operation After Different Excitation Faults

A turbo-generator during asynchronous operation after the excitation fault can absorb lots of reactive power and result in the increase of the leakage flux and losses in the stator end region. In order to study the loss distribution of the stator end structural components during asynchronous operation, this paper presents a method combining the 2-D field-circuit coupled time-stepping finite element model (FCCTSFEM) with the 3-D transient electromagnetic field in the end region of the turbo-generator. The asynchronous processes of the turbo-generator under the open- and short-circuit faults of field winding are calculated by FCCTSFEM, and 3-D transient electromagnetic field and the losses in the stator end region of the turbo-generator are calculated. From the detailed performance evaluations by the 3-D finite-element analysis, the flux densities and loss distributions of the stator end structural components are compared under different excitation faults. The influence of the metal shield material on the flux densities and losses of the stator end region is studied. The variations of the losses in different stator end structural components are revealed along with the conductivity of the metal shield. The results could provide a theoretical basis for improving the asynchronous operating ability of the turbo-generator after the excitation fault.