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II1SItLL-T ~ PAPER W. McMahon Bell Telephone Laboratories, Inc. Murray Hi 11 , New Jer ~ ey Canacitore Capacitors _ Their Use in Electronic Circuits] - M. Brotherton. This emalLl (104 ~age) volume contains a description of the electrical, physical and chemical properties of imp~egnat;ed Cater ce~nacitors as spell as their various applications in electronto circuite. Besides this most of the Rena jor improvements in the manu- facture of ca~aci\Q~ in recent years are described briefly. Capacitor Life Teating2 _ J. R. Weeks. Equipment and techniques he described for making accelerated teats of capacttore largely of the impregnated parer type. In tests which are acceder rated by employing DC droll age higher than that to which the capact- t~ors will be subjected in service the fifth power rule is used to estimate the probable life of the test units. Men elevated tem- nera~Gure ts the accelerating agent, it is found that the life of impregnated caner capacitors is approximately halved by each 10Ce increase in temperature. Dielectric Proper _ Studs es of Dielectric Properties of Chemical Pulps3 - Cyril Delevanti, cr., and P. Be Ragmen. The authors have devised apparatus axed developed a technique for measuri ng; the dielectric constant and dielectric loas of paper sheets. Data on these pro_ er~ciea There obtained, using a pulp of known`; chemical corapositior~. Their findings indicate that es the quantity of abe orbed metallic ions increases the ~ one - factor increases; especially at higher frequencies and that dielectric constant is slightly increased bar increasing metal ion content. Lignin in paper appears go contr1- b '.te largely to its loas factor. On the other hand, lignin due to its chemical nature Probably effectively ties up appreciable quan- titie~ of ions occurring in dielectric impregnants. This augges~Ge that unbleached pulp may be best sulted for DO anplicatione whereas bleached fibers may be more satisfactory for AC applications. The experimental re su] ts were all obtained on uni~regna4Ged paper and the authors make no predictions of applicability to impregnated caner combinations. Studies of Dielectric Propertles of Chemical Pulpa4 - D. O. Adams. The dielectric strength of unimp~egnatea cab] e paver was measured under various conditions. All samples were tested in an atmosphere of nitrogen. The effects of gee Pressure, relative humidity, ternpera~Gure, sheet density and sheet thickness were studied. It was found that the dielectric breakdown gradient _ 101

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increased &9 gee pressure increased but decreased with lncreasl~ relative humidity, temperature, sheet Penalty and sheet thickness. The effect of gas pressure appeared to be most Pronounced. A theory is offered to explain the. behavior of the paper under these various conditions. The author concludes that the breakdown gradient of a sheet of paper in a gas 18 not a measure of the ln- trinelc dielectric strength of either the paper or the gas. Rather it is a complex phenomenon involving the dielectric strength of both. Moreover, in view of his theory, the author feels that it is difficult, if not i~oasible, to translate the breathe own per_ romance o' ur~impregnated paper in the gas to that of oil or resin impregnated paper. He suggests that, while the lack 02- correlation between the dielectric strength of nape r as tested in air and its performance in service is frequently attributed to variations in impregnation, the true cause may lie in the fact that the mechanism of breakdown i n air is quite different from thug in oil. Some Properties of Insulation made from Ceroa Fibers - R. C. Should. Mr. Sproull has investigated the comparative re- activity of Caroa paper and Manila paper when aged at 1250C. in the presence of chlorinated diphenyl. Re concludes that the f ormer is at ~ east as stable as the latter and both are satisfac~Gory for use in insulation impregnated with chlorinated aiphenyl. As for electrical characteristics, the power factors of the two papers are practically identical up to 80 Then compared on the game density basis. From 80e to 100 the power factor of Manila pacer increases more rabidly than that f or Caroa. The dielectric strength measure_ meets of the two ne.~ere' which were made Edith various coil struc_ tureo and ale o paired 'sires, indicate that Caroa is the equal of Man' la paper. . ~52 Paner Ca~acitor~ Containing Chlorinated Imp~egnants6 - L. Egerton and D. A. McLean. This paner i8 one bt a groun on the mechanism of stabilization of chlorinated impregnants in paper canacito-e under electrical stress. The authors had previously .. . established the fact that the edition of small amounts of certain organic coonhounds, notably quinones and nitroaroma&cics, to chiori- nated diphenyl or chlorinated naph~Ghalene considerably enhanced the life of aluminum foil paper condensers impregnated with them. On the hypothesis that hydrogen chloride, Split out of the im- ~regnant, sets off a chain of reactions which ultimately destroys the dielectric, the authors have inves~Gigated the effect of these organic additives in impregnants satura~Ged with hydrogen chloride. Tt Auras found that the conductivity of the EC1 ~ olution, which was quite constant ~ was not altered by the addition of the se ste.bi~ ~ zing comnoancis. However ~ when aluminum foil was added to the impregnants .~. saturated Edith HC1 their conductivity increased rapidly after a brief induction period and the aluminum was consumed. Adding stabilizers to this System Ore vented corrosion of the aluminum and hence conductivity sea not increase. The authors conclude that these compounds stabil Size impregnated condensers by forming a - 102 _

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protective file on the aluminum foil. They feel it is signi- fice.nt thet Al stabilizers discovered thus far are oxidizing agents to some degree arid they theory ze that either an oxide or organic metals ic tiles is formed on the metal which prevents corrosion. Paper Capacitors Containing Chlorinated Im~regnants _ Effects of Sulphur - D. A. McLean, L. Egerton and C. C. HOutze This paper deals with another chase of the we on stabilization of paper caT,acitor~ containing chlorinated impregnants. A com- crehensive study is recounted or the eff ects of the element Bull chum in cavort made of linen pacer and of Eraft paper with electrodes of either tin or aluminum acrid impregnated **pith either chat orine.ted nanhthalene or ch] orinated diphenyl. A appall amount of Arthur adcled to the dielectric ~mpre~ant yielded a marked extension to the life of capacitors tested at high temperatures. Moreover, the capacitors had a lower and more stable power factor; an effect Rich was more pronounced with tin electrodes than with aluminum. The authors believe that the manner in which slur nerttorme this feat is through formation of a protecting film or, the surface of the electrode. Electron diffraction patterns of the surface of tin electrodes used in these e~ertrnents revealed e. layer of tin aulphide on the surfac e which supports the c on clued or`. Belf'_Healing Capacitors - Fred E. Henderson. This is an abstract of Mr. Rendereon's report on "Manufacture of Metal_ lined Paper Fixed Ca~acltor Units by The Robert Boach company, Stuttgart, Germany This process comprises lacquering one aide of. condenser paper and then condensing a very thin film of zinc on the lacquered surface to form an electrode. The lat~Ger step ~ ~ carried out in a thoroughly evacuated chamber in which the Darer is massed over ~ pot of molters zinc. Condensers made Erich . . . metallized paper are more compact than the conventional foil type, i.e. their ratio of capacity to physical volume is higher. Bealdes this, they do not fall in the same manner as the f oil type cons densers. Then e. short circuit occurs the very thin zinc film behaves like a fuse and the metal Nburns away" from the point of short circuit, thus opening it. Because of this, capacitors of this type are termed "~eIf-healing". Some data are given on manufacturing requirements and procedures Bosch Process _ Metallized Paper9. The Bosch process for metallizing paper for car~acitor~ is described. This article contains a number of photographs of the German equipment which was shipped to this country and Bet up and operated in the Western Electric Company experimental shop in Chicago. Metallized Paper Capacitorel - S. J. Borgare arid others. A British intelligence team headed by Lt. Borgars compiled this report on the process for making metallized Caper capacitors _ 103 ~

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developed by the Germans. Part ~ of the report contains infor_ mation on the ~re~eratlon of paper for this process as T>ractiaed by the Germans ~ The manufe~c Cure of capacitors with this tO deseribea tn P=t II. _ 104 .

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BIBLIOGRAPHY 14 0, Van Nostrand Co., New York City (1946) 2. Bel:L Laboratories Records 24, No. 8, 296, Aught (1946) 3. Paner Trade J., I, NOe 25, 35, December 27 (1945) 4. Pager Trade J. ~ 122,, No. 79 43-52 (T.S. 63-72) Feb. 14 (1946) 5. Paper Trade J. 91 123, 142' October lO (1946) 6 ~ Ind. Eng. Chem., 3~3, 512, May ~ 1946 ~ 7. Ind. Eng. Chem. ,, AS,, lllO, November (1946) S. Product Erg. 17, ll7-~3, September (1946) 9. Chem. and Eng. Nears, At, 3356, December 25 (1946) 10. PB 39361 _ }Hobart Publ. Co., Box 4127, Cheery Chase Stetion, 'Washington 15 , D. C., Nov. 1 (1~46 ) _ 105 -