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 Resistance of Connectors with Different Contact Finishes under Low Level Conditions
In order to find out the behaviors of the contact resistances in the low current and low voltage range before physically starting the fritting phenomenon, several connector designs and contact finishes were investigated. The used finishes were hard-gold, silver, hot dip tin and electroplated tin. Similar coating combinations, in addition to different coating combinations, are used for these investigations. The environmental degradation was conducted by applying sequentially high temperature storage, mixed flowing gas and high humidity storage. Our investigations with new and degraded samples show that neither measurement methods nor low level current used for the measurements result in a difference in electrical resistance of new or environmentally degraded connectors. No fritting process was observed at relevant current levels. A measurement of contact resistance at the 100 mA level should adequately ensure performance at any lower level of current. Many metrological and instrumental efforts due to fritting can therefore be reduced.
Laminar heat or mass transfer in rectangular channels and in cylindrical tubes for fully developed flow: comparison of solutions obtained for various boundary conditions
Abstract A comparison is made of results obtained with various boundary conditions at the wall of the channels. By comparing blood Sherwood numbers for finite wall resistance with those for constant concentration boundary condition only a small variation is found for various points along the blood channel.