Damper cages in genset alternators: FE simulation and measurement

This paper describes an investigation of the function and effectiveness of the damper cage in small salient pole genset alternators. A time-stepping finite-element (FE) simulation is described and its application to the damper circuit is validated through the use of a specially manufactured rotor with wound damper coils. Further validation is provided by comparison of measured and predicted stator and main field quantities in a standard machine when subjected to sudden application of load. The simulation is then used to predict the performance of the alternator with and without the dampers for balanced and unbalanced load conditions. The effect of the damper circuit is also investigated when a nonlinear, rectifier load is applied to the machine with the modified rotor.