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.
Recent advances on electrical contact resistance: Theory and experiment
Summary form only given. Electrical contact is important to thin film devices and integrated circuits, carbon nanotubes based cathodes and interconnects, field emitters, wire-array Z pinches, metal insulator-vacuum junctions, and high power microwave sources, etc. Because of the surface roughness on a microscopic scale, true contact between two pieces of conductors occurs only at the asperities of the two contacting surfaces, leading to contact resistance. For a long time, the basic model for contact resistance remains that of Holm's a-spot, where the current flows through a circular disk constriction of a small radius a and zero thickness at the bulk interface. In this paper, we vastly extend Holm's a-spot theory to higher dimensions, including dissimilar materials in the main current channels and in the connecting bridge joining them. Both Cartesian and cylindrical channels have been analyzed. A scaling law for the contact resistance has been constructed for arbitrary values of the dimensions of the channels and bridges, and for arbitrary electrical resistivity in each section. This scaling law was confirmed against spot checks with the MAXWELL 3D code. It also recovers the same results for all known cases, including connecting bridges of the same resistivity. This latter special case was also confirmed in our recent experiments.
A technique for large-field, superficial electron therapy.
The application of electron beams to radiation therapy has received increased attention in recent years. This interest stems largely from the special characteristics of the electron depth-dose distribution; the fall-off in depth dose near the end of the range of the electrons is particularly rapid for electron beams having energies less than about 10 Mev. Such an electron beam is suitable for the treatment of widespread, superficial lesions, where it is desirable to minimize the dose to deep tissues. All the common sources of super-voltage x-rays, apart from radioactive substances, are inherently capable of producing an external beam of electrons, though with varying degrees of complexity. Electrons of about the energy suitable for superficial therapy (several Mev) may be used to produce an x-ray beam which is sufficiently penetrating for the treatment of even the deepest lesions. The Stanford medical linear accelerator was designed to provide both x-rays and electron beams. The accelerator and its applic...