Hybrid DC Molded Case Circuit Breaker Technology

The demand for DC circuit protection products continues to grow as industry sectors such as electrical vehicles, energy storage and data centers further expand. It drives the need for cost effective and compact DC circuit protection devices with higher short circuit interruption ratings. This paper presents a novel hybrid DC molded case circuit breaker (MCCB) technology that enables single-pole 10kA/600VDC interruption capability. The design is based on existing MCCB switching mechanism and contact structure. It incorporates a galvanic isolation disconnect without adding Watt loss to the device when it is switched on. Unlike conventional hybrid breaker topologies that try to commutate the fault current as quickly as possible from the electromechanical path to the power electronic path, this hybrid MCCB topology utilizes the arc to absorb most of the inductance energy stored in a DC electrical system and to limit the fault current to a lower level before the commutation. Concept prototypes have been developed and investigated via both numerical simulation and experimentation. Test results show that this technology enables the DC single-pole MCCB to be able to not only interrupt 10kA/600VDC fault current, but also maintain the thermal performance of a conventional MCCB.