*Article* **Research on Vacuum Arc Commutation Characteristics of a Natural-Commutate Hybrid DC Circuit Breaker**

### **Dequan Wang, Minfu Liao \*, Rufan Wang, Tenghui Li, Jun Qiu, Jinjin Li, Xiongying Duan \* and Jiyan Zou**

School of Electrical Engineering, Dalian University of Technology, Dalian 116024, China; wdq@mail.dlut.edu.cn (D.W.); Wangrufan@mail.dlut.edu.cn (R.W.); litenghui@mail.dlut.edu.cn (T.L.); qjun@mail.dlut.edu.cn (J.Q.); jinjinli@mail.dlut.edu.cn (J.L.); jyzou@dlut.edu.cn (J.Z.) **\*** Correspondence: LMF@dlut.edu.cn (M.L.); dxy@dlut.edu.cn (X.D.); Tel.: +86-198-1899-7875 (M.L.)

Received: 8 August 2020; Accepted: 12 September 2020; Published: 15 September 2020

**Abstract:** Vacuum arc commutation is an important process in natural-commutate hybrid direct current (DC) circuit breaker (NHCB) interruption, as the duration of vacuum arc commutation will directly a ffect the arcing time and interrupting time of NHCB. In this paper, the vacuum arc commutation model of NHCB was established by simplifying solid-state switch (SS) and vacuum arc voltage. Through theoretical analysis and experiments, the vacuum arc commutation characteristics of NHCB were studied. The mathematical formula of the e ffect of main parameters on the duration of vacuum arc commutation is obtained, and the changing law of the influence of the main parameters on the duration of the vacuum arc commutation is explored. The concept of vacuum arc commutation coe fficient is proposed, and it is a key parameter that influences the vacuum arc commutation characteristics. The research on the characteristics of vacuum arc commutation can provide theoretical foundation for the structure and parameter optimization of NHCB and other equipment that uses vacuum arc commutation.

**Keywords:** hybrid dc circuit breaker; vacuum arc commutation; solid-state switch; vacuum arc voltage
