Transformers Rectifiers and Inverters
Unlike in the public utility sector, traction power transformers operate with a single phase and step down the high voltage to the contact line voltage of 15 kV or 25 kV.
All transformers used are either self- or forced-aircooled, oil-immersed transformers with typical power outputs between 5 MVA and 85 MVA.
Sitras TCR controlled thyristor rectiﬁers are used to supply power to DC railways. Up to a certain loading current, they are capable of keeping the supply voltage of a substation to an almost constant level.
Sitras TCI thyristor controlled inverters are used in the power supply system of DC railways. Through the parallel connection of such an inverter, DC substations equipped with diode rectifiers can acquire the capability to return surplus energy to the system.