Zależność jakości energii sieci trakcyjnej od zastosowanych układów transformatorów prostownikowych

Tram lines in Poland are supplied from the power grid via transformer-rectifier sets, with primary three-phase transformer windings wye- or delta-connected, and secondary side windings connected in accordance with desired number of phases. The number of pulses in rectified dc voltage depends on transformer used. Supply voltage may be either purely sinusoidal and symmetrical, or it may be distorted, or asymmetrical, or both. The paper presents several different transformer types, which are used or may be used in energy transformation and shows the results of investigating dc traction voltage quality and power grid current quality depending on transformer-rectifier set used and quality of supply voltage. The transformer types analysed are 9-phase, 2x6-phase, 12-phase and, for comparison purposes, 6-phase. The resulting dc waveforms are shown together with results of calculations covering THD vector value for different supply conditions. Results of laboratory tests are presented as well. Interesting effect of 24-pulse system changing into 6-pulse system is marked.