The paper deals with the problems introduced by a fully controller rectifier with thyristors (FCTR), used in the supplying circuit of a power plant's excitation winding. The rectifier is supplied from the secondary winding of a 3.256 MVA, 24 / 0.65 kV power transformer (PT), in a schema modified with respect to the excitation supplying from an auxiliary generator. The use of PT supplied from the main generator's terminals resulted into new technical issues, which were not considered when choosing this solution (e.g. influences through conduction or inductive coupling over other components from the power group). The paper presents the excitation circuit's schema along with few observations over the equipment — a Data Acquisition System (DAS), especially designed and realized for tests in this specific framework. The waveforms corresponding to the three-phase voltages and currents at the FCTR's input, recorded with the DAS, are presented. Power quality parameters of the recorded waveforms were determined. They are valid for all recorded waveforms in distorting regimes. There are presented the waveforms recorded at the FCRT's output, along with the powers absorbed by the excitation winding from the FCRT. Parallel analyses (based on Fast Fourier Transform and respectively on Discrete Wavelet Transform) were performed. Also were computed the powers flowing between the FCRT, the excitation winding and the transformer used to supply the excitation winding. A reduced value of the power factor was noticed for the input in FCRT. The analyzed harmonic currents and the power flows generate new power quality (PQ) and respectively Electromagnetic Compatibility problems (including related Electromagnetic Interference problems), witch are not addressed by the existing standards. The conducted disturbances transmitted through conduction or inductive couplings affect other neighboring equipment as well. The solutions for their limiting rely on active or hybrid filtering. The level of the total harmonic distortion and on the power factor will depend on the new standards (which must be adopted).