Medium size rotating machinery upgrading: design criteria and technologies

After some considerations on the expediency of rewinding an old machine, the authors summarize the techniques applicable to medium size induction and synchronous machines, pointing out the problems which may arise and the advantages provided by the new materials and technologies. The advantages derived from an electromagnetic redesign of the machine are also considered. Some specific topics related to the revamping of rotating machines are examined. Specifically, the most recent developments in the field of excitation systems, variable speed drives and diagnostics are discussed