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 affect 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 effect 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 coefficient 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.

It is a valuable subject for academic community how to limit the short-circuit current within the breaking capacity of breakers at all levels. Liquid metal current limiter (LMCL) can tackle this challenge with its unique advantages. However, liquid metal and cavity of the existing LMCL are severely eroded, which limits the application. From the perspective of increasing the response speed, improving current-limiting efficiency, and reducing erosion, this article designs three LMCLs with polymethyl methacrylate (PMMA) material, ZnO pulse power resistance (ZnO PPR) material, and Kovar 4J29 material as the wall. Specifically, the wall is an important part of LMCL cavity with a channel. In addition, there is a discussion about the reasons for the different arc plasma intensity between the insulating wall LMCL and the resistive wall LMCL, from the point of current distribution. Furthermore, for Kovar 4J29 wall LMCL, the development process of the arc plasma is analyzed, and the effectiveness of the resistive wall LMCL is proven. Finally, the five current-limiting parameters of the three LMCLs under different short-circuit currents are compared and discussed. This article opens up a new approach for parameter optimization research and diversified development of LMCL.

The armature of the electromagnetic reconnection launcher (EMRCL) plays a key role in accelerating large-mass loads, which have attracted extensive attention in past years. In this article, the effects of the armature thickness, length, and width on the performance of the EMRCL are analyzed for designing a high-strength and high-efficiency armature. First, according to the deformation and Von Mises’ stress distribution of the armature in the electromagnetic structure field, the armature thickness should be six times the skin depth. Then, the orthogonal experiment method results demonstrate that the armature speed tends to a saturated value with increasing length and width. Finally, a three-stage EMRCL platform with a load of 10 kg was constructed to verify the accuracy of the simulation results of three armatures with different lengths and widths. The experimental results show that the speed of 80 $\times120$ mm ² armature can reach 11.26 m/s, which is a significant increase of 23 times than the 40 $\times120$ mm ² armature and is consistent with the simulation results. It indicates that the optimal armature length is 1.2 times the coil length, and the optimal width is 1.3 times the coil width. This research provides a valuable reference for the armature design of EMRCL.

Recently, effectively improving the energy conversion efficiency (ECE) of electromagnetic launch (EML) systems has been one of the most pressing problems facing engineering applications in defense technology, transportation, and so on. This article offers a solution to directly increase the inductance gradient ( $L ^{\prime} $ ) to improve the efficiency of the electromagnetic reconnection launcher (EMRCL) system. First, three types of coils were fabricated, and the inductance was measured by LCR bridge meter. Next, to verify the performance of these coils, a five-stage launch platform was built, and the experiment results are consistent with the simulation models. The experimental results showed that $L ^{\prime} $ of the double-layer horizontal-winding coil could reach 251 $\mu \text{H}$ /m, which is 3.5 times that of the single-layer vertical-winding coil. The region greater than 100 $\mu \text{H}$ /m accounts for 70% of the coil length, and the efficiency is 2.5 times that of the double-layer vertical-winding coil, $\sim 1.21$ % with a payload of 11.5 kg. This indicates that the winding method with an improved $L ^{\prime} $ may meet the lower current and higher efficiency requirements of the EMRCL system.