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Clear ruby muscovite mica is classified as a low loss insulating material and many values for dielectric loss and dielectric constant are given in the literature. Such values presumably are based on measurements made in the direction perpendicular to the plane of basal cleavage. We find that mica inherently has a much higher dielectric loss parallel to the plane of cleavage and that impurities such...
Tests with high voltage d-c are generally facilitated as compared to a-c testing by the fact that, with d-c, test terminals may be greatly simplified or omitted entirely. For example, tests have been made at 500 kv with a test end only six feet in length and with no special end preparation whatever.
As might tie expected from the title, the purpose of this paper is not to cover all possible phases of the use of silicones in electrical applications, but to describe a few of the “new” silicones which are available, or about to become available to the electrical industry.
The voltage distribution on high-voltage insulators should be uniform enough to prevent excessive voltage gradients and spark discharges under any practical working conditions. Furthermore, uniform voltage distribution is, in general, essential for the efficient use of the insulating material.
One of the drawbacks of ceramic dielectrics is low thermal stock resistance. This proved quite troublesome to the armed forces during the last war by causing failures of electronic equipment.
One of the first applications of microwave techniques for determining dielectric properties of gases was made by Saxton who determined the dielectric properties of steam at 9 cm, 3.2 cm, and 1.6 cm.1 He found a dispersion which he was unable to account for theoretically. Saxton's results and those obtained at lower frequencies by other investigators are shown in Table 1. The present work was undertaken...
The low frequency dielectric properties of 1-monopalmitin, 1-monostearin, 1,3-dipalmitin, 1,3-distearin and a number of long-chain triglycerides have been investigated in the solid state over a wide range of temperature, The measurements were made with the aid of an impedance bridge operating in the frequency range from 0.5 to 100 kilocycles.
The microwave resonance technique of L. R. Bickford, Jr.1 of this laboratory is being used in a further study of single crystals of magnetite (Fe3O4). His measurements were made using 1.25 and 3.3 cm microwaves on both natural and synthetic single crystals from room temperature to −190°C. These measurements are being extended to lower temperatures using, synthetic crystals and 1.25 cm microwaves....
The dielectric constants of cellulose fibers from a number of sources have been measured by a liquid immersion method. The dielectric constant of the fiber is matched exactly to that of the liquid in a dual electrode cell using a null method. The dielectric constant of the liquid is varied by varying the temperature, making use of the large negative temperature coefficient of its dielectric constant...
The voltage endurance of insulation on machine windings is of considerable interest to both manufacturers and users of electrical equipment. It was believed that additional information might lead to a better understanding of dielectric break-down such as occurs on windings and aid in the development of maintenance testing procedures for older windings∗ Previous test work had been on older windings...
Silicone resins are used as dipping, varnishes and coatings for glass cloth and glass covered magnet wire, primarily in applications in which high ambient or operating temperatures obtain. The silicone resins often must be depended upon to maintain electrical and mechanical properties required in the specific application for long periods at temperatures as high as 180°C or even higher. The physical...
A number of applications of synthetic resins most of which have only recently been applied to any extent in the electrical industry, are briefly described.
Conference proceedings front matter may contain various advertisements, welcome messages, committee or program information, and other miscellaneous conference information. This may in some cases also include the cover art, table of contents, copyright statements, title-page or half title-pages, blank pages, venue maps or other general information relating to the conference that was part of the original...
Everyone concerned with the measurement of the properties of dielectrics has probably been faced with the problem of measuring the dielectric constants of thin films. “Thin films” are understood to mean varnish, resin or other solid dielectric material not more than a few mils thick. It is the purpose of this paper to discuss some of the methods used, their advantages and limitations, and to suggest...
The apparatus shown in Fig. 1 has been developed to measure, compute and record dielectric constant and loss factor against temperature at any fixed frequency from 25 to 600,000 c.p.s.
The question of electric shock hazard from the surface of an energized cable was deemed of particular importance in view of a recent trend towards use of semi-conductive jackets. The data and discussion have to do specifically with this aspect. Whereas our preliminary experimental investigation was initiated with aerial cable, the implications are general and should provide a stimulus for further...
The preliminary object of the research described here was the investigation of a suspected variation of breakdown strength with duration of the applied voltage pulse. The liquids chosen as test dielectrics, both polar and non-polar, were of simple molecular structure, the majority of them being organic liquids.
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