Research On Damper Winding Losses And Influence Of Damper Winding Currents In Hydro-Generators

In recent years, with the improvement of design level and manufacturing process, the unit capacity of hydro-generator is also increasing. The electromagnetic load and thermal load is generally higher for large hydro-generators, and the problems due to additional losses, heating and vibration of generating set also become more serious. So it's essential to analyses and calculate the operating performance of generators deeply, to ensure the safety and stability. The engineering problem of damper winding losses calculation in hydro-generators has been studied and related research work has been done in this thesis.Firstly, based on rotating air-gap permeance model and damper circuits, a calculation model for induced currents and additional losses in damper winding is established according to electromagnetic induction principle, and with this model the damper winding losses of generators operating on different conditions, including no-load, rated-load, rectification load and unbalanced load conditions, can be calculated quickly and accurately. Then the described model is applied to a salient-pole synchronous machine, and the damper winding losses of this machine under all four operation conditions are analyzed and calculated, also the calculation results are compared and validated with simulations of finite element model. Based on the calculation results, the influence of key damper parameters on additional losses is discussed, including damper pitch and diameter of damper bar. Finally, Space harmonic and time harmonic of additional magnetic field by induced damper currents is studied, the influence of additional magnetic field on the air-gap magnetic field harmonics and on the harmonic EMF of armature winding is calculated according to the calculation results of damper winding currents, also the effect on no-load EMF played by changing damper pitch is studied.The calculation model described in this thesis provides the designers with a quick prediction for damper winding currents and power losses, which can benefit the optimization design of parameters for generators, and the research on additional magnetic field by induced damper currents provides a foundation for follow-up studies of electromagnetic vibration force and additional electromagnetic torque.