Modeling and experimental verification of a hybrid DC breaker during fault interruption

One of the key-enabling technologies of low inductive low voltage direct current (DC) systems is a breaker that can interrupt fault currents in less than a millisecond to avoid large fault currents. In this paper, the interruption capability of a hybrid breaker's solid-state branch is analyzed with and without a resistive-capacitive-diode (RCD) snubber. Simulation models were used in tandem with experiments to study the peak insulated gate bipolar transistor (IGBT) voltage and junction temperature at 3800A. It has been shown that, in the absence of a snubber, the switching energy losses increased by 160%. It has also been shown that at 3800A, the switching losses amount to 30% of the total losses. Hence this has little contribution to the IGBT junction temperature rise. Consequently, omitting an RCD snubber results in significant size and cost reductions at the expense of a 20% increased peak voltage during the turn-off process. This however can be mitigated by alternative cost-effective methods such as decreasing the stray inductance or switchable gate resistors.