Conceptual Design of Bidirectional Hybrid DC Circuit Breaker for Quench Protection of the CFETR

This technical note presents the conceptual design of bidirectional hybrid dc circuit breaker for quench protection circuit (QPC) of the China fusion engineering test reactor. The rated parameter of bidirectional hybrid dc circuit breaker is up to 70 kA and 15 kV. The novel scheme based on a mechanical breaker and the controlled static circuit breaker (SCB) in parallel is proposed. The mechanical breaker consists of three independent control contacts to realize the rapid transfer of the large current and fast recovery of dielectric strength. The SCB is composed of the insulated-gate bipolar transistors (IGBTs) unit and four diode units in a rectifier scheme for both current directions. Moreover, the feasibility of bidirectional dc circuit breaker, such as the turn-on reliability of IGBTs unit, and voltage sharing and current sharing of each IGBTs are investigated in this technical note, finally, the conceptual design result of the QPC is given.