About the static excitation system with a fully controlled rectifier

The paper analyzes the potential influence of a rectifier fully controlled with thyristors (RFCT) over some components of a power group with static switching. Problems related to the active power flows in distorting and/or non-symmetric regime are briefly presented. Also there are revealed issues related to the influence of non-linear and/or non-symmetric receivers of active powers over the active powers flows along power non-symmetric components when superior harmonics are considered. One presents a complete system with static excitation from a power group. The supplying is made from the power group´s main generator terminals, through a power transformer and a RFCT. The electric quantities were recorded with data acquisition systems (DAS) specially designed and made for this application. Based on the acquired recordings one used an original dedicated software based on Fast Fourier Transform (FFT) that allowed the determination of some power quality parameters and the calculation/displaying of (re)active powers´ components for each phase and respectively for the significant harmonics (whose weights are over 1%) at the RFCT´s input. Analyzing the results one could conclude that the RFCT behaves like a “power converter” for the harmonic and/or non-symmetric powers. An influence of harmonic and non-symmetric powers over some components of the power group could be noticed as well. Experiments certified that these influences result into the shortening of some components´ lifetimes, owing to the power flows along the superior harmonics and non-symmetric powers.