Improving Fault Current Interruption Capability of Contactors in EV Battery Packs with SiC MOSFET Commutation Circuit

A Hybrid Circuit Breaker (HCB) solution is proposed to improve the DC fault capability of the DC contactors for Li-ion battery protection in EVs. The common short-circuit protection of EV battery packs is achieved through fuses, while the DC contactors are not supposed to switch any current. However, the intrinsic levitation force of DC contactors can separate the contacts during short circuit events where ares are generated and damage the contactors. To protect contactors damage from this behavior, the pack fuse selection has to be either fast or controllable, so that the fault current can be interrupted before levitation happening. This lays the motivation of this paper. The proposed approach uses a 1200V/700A SiC MOSFET power module to commutate the fault current and help extinguish the contactor arc due to its levitation under the high fault current. A prototype is designed, built, and tested to 400V/600A. Compared to the prior art contactor, the HCB can potentially eliminate the need of a series fuse and extend the lifetime even for normal load current switching.