A methodology to remove Stator Skew in Small-Medium Size Synchronous Generators via innovative damper cage designs

Stefano Nuzzo (University of Nottingham)

CHALLENGE - The technique proposed in this study is aimed at removing the need for the traditional stator skewing that is so commonly used in synchronous generators to achieve acceptable values of voltage total harmonic distortion. 

SOLUTION - A non-standard damper cage configuration is proposed that comprises modulation of the damper bars’ positioning. An off-the-shelf, 400kVA generator is used as a benchmark machine. Its rotor is optimized using modeFRONTIER software in order to minimize noload, line-to-line voltage THD and, at the same time, the damper cage loss.The first phase is performed by using design of experiments (DOE) techniques. The second phase of the procedure is that of performing a first exploration of the design space by using a multi-objective genetic-algorithm (MOGA), which is based on a scheduler designed for fast Pareto convergence. 











BENEFITS - The proposed concept has been experimentally validated on a full-scale prototype. The prototype achieved a THD equal to 2.29% and an improved efficiency of 0.23%, while keeping the no-load, full-load and transient requirements the same as the existing alternator.