280A Switched Mode Charging Rectifier for Three-Phase Mains

The large new digital telephone exchanges which are installed in Norway today require considerable amounts of power. This results in a large demand for 48V battery plants and charging rectifiers. This paper describes a 15kw switch-mode 48V charging rectifier for 3-phase mains. The rectifier can very easily be coupled from a 3-phase 230V AC mains to a 3-phase 415 AC mains. A single phase working mode is possible with reduced power output. The rectifier system also has the advantage that the mains current waveform is nearly sinus-shaped. The system has a strictly modular construction and comprises a cabinet, one control module and two rectifier modules. The rectifier unit is a secondary switch and can deliver 60V DC and 140A. Bipolar transistors are used for switching with a switching frequency of 25 khz. Both the rectifier units and the control unit have a strictly modular construction and can be replaced during normal service. Current sharing occurs between the rectifier units, and between several parallel-coupled rectifier systems, without using master/slave configurations.