Scientific paper ID 1714 : 2018/3

The traction power supply of the urban electric transport (UBE) is provided by DC traction power stations (DCTPS). Main element of the (DCTPS) is the traction power supply unit (TPSU), which is built up by traction rectifier (TR) and traction transformer (T-TR). According to the type of T-TP and TR, two types of TPSU that are mainly operated at the DCTPS of UBE in Bulgaria.

The first type of TPSU is built from a standard three-phase T-TR and three-phase TR, which are connected in ”Laryonov” bridge circuit.

The second type of TPSU is made of a special T-TP with one primary and two secondary windings. The secondary windings of T-TP are connected respectively in a star and delta scheme thus creates six phases which are shifted to each other at 60 electrical degrees. To the secondary windings of T-TP is connected six phase TR which is also ”Laryonov” circuit.

On the basis of data obtained from the experimental measurements in the paper, an analysis and comparison of the technical characteristics of both types of TPSU was made. It has been made an evaluation to which point the kind of TPSU determines the quality of the strained voltage, the parameters of the electrical energy including the losses and how these quantities depend on the number of pulsations of the rectifier.