The influence factors experiment of poor contact discharge in indoor power grid
In order to achieve monitoring on poor contact in indoor power grid and avoid electrical fires, the discharge phenomenon caused by poor contact is experimented systematically. A discharge experiment model of poor contact is developed, in which the influence of the structural parameters of contact type and the gap distance on poor contact discharges are experimented, and the influence of the operating parameters of load type (cos φ), load current and voltage phase are experimented too. The influence factors of initial discharge and the influence regular patterns with various parameters have been obtained from a large number of experiments. Statistical results show that the discharge trend increases first and then decreases. In the range of experiment load, poor contact discharge is very sensitive to the structure parameters of contact model, in comparison, it is not sensitive to operation parameters such as load type and load current. When the phase of experiment-voltage is in the vicinity of 0°, 60°, 120°, 180°, 240°, 300°, it has intensive discharge region of poor contact, and this phenomenon has the similarity under different factors.
Electrical contact phenomena in switching technology - Arc discharges in switching contacts
Arc discharge phenomena upon opening and closure of switching contacts operated in load current ranges up to several tens amps are briefly summarized. Based on the electrical circuit conditions, different types of arc discharges will occur when contacts are opened. Such arc discharges will have certain influences on contact reliability and lifetime through material transfer and erosion, formation and deposition of arc products, and resultant increases in contact resistance. Arc discharges upon contact closure can be basically considered as breakdown, although break arc discharges can be also observed at contact bounces. Moreover, the author's recent studies indicate that the “minimum arc current value” of contact materials is not actually the lower limit of break arc occurrence and its interpretation should be changed.
Effects of reservoir volume on performance of pulse tube cooler.
A pulse tube cooler has the advantages of long-life and low-vibration over conventional cryocoolers such as G-M and Stirling coolers because of the absence of moving parts at low temperature. On the other hand, the combination of a reservoir and orifice is indispensable to optimize the performance of pulse tube coolers. In order to make the pulse tube cooler compact for practical applications, the volume of reservoir should be minimized. This paper analyzes the effects of the reservoir volume on the thermodynamic performance of various components in a simple orifice and a double-inlet pulse tube cooler by combining a linearized model with a thermodynamic analysis. Expressions of entropy production for those components are presented. The results show that the reservoir volume has a significant influence on the entropy production in the various components when the reservoir to pulse tube volume ratio is smaller than about 5. The ratio is important to determine the minimum reservoir volume for a pulse tube cooler. Optimum settings for a double-inlet pulse tube cooler are also discussed.