Cong Jiyuan

The analysis of high-speed repulsion actuator and performance comparisons with permanent magnetic actuator in vacuum circuit breaker

The high-speed operation switchgears are required by more and more situations in power system, such as high-speed DC circuit breaker and some power-transfer locations. In this paper, a novel vacuum circuit breaker with high-speed repulsion actuator is designed, where, the characteristics of high-speed repulsion actuator are analyzed with finite element method (FEM) through changing design parameters of repulsion actuator, and good trends for generating bigger force are given. The performance comparisons with permanent magnetic actuator (PMA) are also given in this paper, experiments shows that vacuum circuit breaker (VCB) based on high-speed repulsion actuator can present good operate performance than PMA.

Arc tracking properties of the aging wires in aircraft

A modern commercial aircraft contains hundreds of miles of wiring. This vastly increased use of wiring, in conjunction with decreased insulation thickness, has increased the incidence of wire-related aircraft safety problems. Due to thermal, electrical, mechanical and chemical overstress, the aircraft wiring will be aged and the wire insulation will be decreased. Microscopic cracking occurs in wire insulation as the insulation ages. The Cracking in the wire insulation can lead to arc burning between metal conductors in aircraft wiring system. Aging wiring and associated deterioration of the insulation increases the potential for arc fault phenomenon to occur in aircraft. In order to investigate fault arc behaviour of the aging wire, the arc tracking tests have been performed with typical aircraft wire BMS 13-60. The video of the arc burning and the waveform of the fault arc have been recorded. The primary test results indicate that wire aging has an important influence on the fault arc behaviour.

Investigation on the Properties of CuCr Contact Material after Cryogenic Treatment

CuCr contact material has been widely used for vacuum interrupters in medium-voltage applications. The microstructure of CuCr contact material is the important factor to determine the properties of vacuum interrupter. In this work CuCr alloys fabricated by normal powder metallurgy are processed by the cryogenic treatment. The microstructure and properties of the contact materials after cryogenic treatment are investigated. Test results show that cryogenic treatment result in fine microstructure of the contact material, especially in Cr composition in CuCr alloy. During the cryogenic process, the low temperature caused the particles in the microstructure to rearrange, which made copper and chromium compositions better distributed. Fine microstructure and uniform distribution of alloys are beneficial to improving the properties of contact materials. The resistance to the arc erosion has been improved greatly by the cryogenic treatment.