Fast Breaking of Currents in Applications up to 800 V DC

The increasing use of DC systems in many different fields requires switching and protecting devices that are developed and optimized for the respective task. A common trait of such applications is the power electronics-based supply of those grids, which severely limits the available short-circuit current and therefore calls for short detection and interruption times of faults. However, as most devices in these applications also contain capacitive filters or DC link storages, there must be a control of the inrush current to avoid nuisance tripping and to ensure selectivity. A more and more common voltage range for the considered grids, e.g., in telecommunications or industrial production sites, is above 400 V up to 800 V [1] [2]. This work therefore evaluates the switching behavior of currently available switching devices subjected to DC voltages of up to 220 V. Based on those results, a novel switching concept is designed and validated. The initial goal is to achieve a switching capacity of at least 400 V and going up to 800 V per single pole in the common device width of 17.5 mm (with DIN-rail mounting) [3] by means of an externally excited magnetic field.