Open Circuit Voltage Distortion in Salient Pole Synchronous Generators with Damper Windings

This paper examines efficient methods for the calculation of open circuit voltage distortion in salient pole synchronous generators with damper windings. It then proceeds to examine the role of damper bars in the level of distortion. The simplified finite element method employed is inclusive of eddy current effects, dynamic field current and full interaction of all MMF sources. It allows accurate total harmonic distortion values to be calculated approximately 25 to 30 times quicker than a fully rotating finite element simulation. Tests have been conducted on eight built machines and results compared to both analytical and alternative finite element methods. The proposed mehtod has an average reduction in error of 55%, compared to an existing analytical method. The presence of damper bars and their position within the pole face is examined, and shown to have a large influence over the level of total harmonic distortion produced.