Design and development of a 7.2 kV/200A hybrid circuit breaker based on 15 kV SiC emitter turn-off (ETO) thyristor

This paper deals with the design of a 7.2 kV, 200 A hybrid AC circuit breaker employing a 15 kV Silicon Carbide (SiC) Emitter Turn-off (ETO) thyristor device as the main semiconductor switch and presents the test results to verify the functions of both the high voltage and low voltage electronic components of the medium voltage hybrid circuit breaker. The hybrid circuit breaker consists a fast acting mechanical switch, a low voltage commutating switch in series with that mechanical switch, a single 15 kV SiC ETO Thyristor device, and a stack of MOVs. This paper focuses on the electronic parts and a companion paper would elucidate the principle and operation of the fast acting mechanical switch. To fulfill bidirectional interruption capability of the high voltage semiconductor device, the SiC ETO is equipped with a low cost silicon diode bridge; a snubber capacitor is equipped in parallel with this diode bridge to alleviate voltage stress of the ETO during turn-off transients. A compact low voltage commutating switch based on silicon MOSFETs has been built and tested up to the full current rating.