Contactless excitation system with rotary transformer for hydro-generators

摘要

This paper presents a new application of contactless electrical power transmission, namely the realization of contact-less excitation systems for hydroelectric power plants. The main excitation systems used in hydro-generators construction are presented, as well as the new solution proposed in this paper. The proposed contactless excitation system for hydro-generators transmits the required electrical energy to the hydro-generator's excitation coil, placed in the rotor, through a medium-frequency rotary transformer, and includes frequency converters on both the primary and the secondary side of the transformer placed on the hydro-generator rotor. In this way, both the advantage of fast static excitation systems (without the high time constants rotating electric machines) and easy maintenance provided by brushless excitation systems is maintained. The design methodology for these non-contact excitation systems is presented, as well as an application for a 75 MW hydro-generator, in operation in Romania.