No abstract

This paper describes the development of a ZOKW off-line switch mode rectifier system to power a large capacity digital switching system which is under development. The rectifier unit uses a double forward circuit topology composed of four power MOSFFT modules. which are controlled by pulse width modulation. This topology can accept a large capacity and enables to reduce the size and weight of magnetic components. The unit is convection-cooled and uses isolated power modules which are mounted on th one end of a heatpipe type heatsink. A well designed heatsink along with a careful choice of pans and components yields an overall efficiency of typically ninety percent. Four rectifier units are housed in a rack cabinet, together with a total control unit which includes distribution, protection. control and alarm.This rack cabinet can be paralleled in modular fashion to any required power level, and installed along with the digital switching system in a switch rwm. This eliminates the need for separate power rwms and distribution busbar layouts.