Influence of Arc Discharge on Contact Erosion and Contact Resistance in a Hybrid DC Switch

Contact erosion due to an arc discharge is a critical problem particularly for a DC switch or a DC circuit breaker. Longer duration arc causes higher degradation of their reliability and lifetime. A hybrid DC switch composed of mechanical switch and semiconductor device decreases the duration of the arc, comparing to conventional mechanical switch. The aim of this work is to examine the influence of arc-discharge duration on the electrode erosion and resistance in opening contacts of hybrid DC switch. In experiment, DC power source and SiC-MOSFET device were connected in parallel with the contact pair. The main current flowing through the contacts varied from 200 to 800 A. When the contacts started separating and the SiC-MOSFET turned on simultaneously, the arc occurred between the contacts and commutated the circuit current from the contacts to the SiC-MOSFET until it extinguished. The arc voltage and current waveforms together with the contact resistance were measured. The contact surface erosion was observed by a scanning electron microscope.