US2266811A - Dielectric for electrostatic condensers and the like - Google Patents

Description

S. RUBEN Dec. 23, 1941.

DIELECTRIC FOR ELECTROSTATIC CONDENSERS AND THE LIKE Filed Sept. 19, 1939 2 Sheets-Sheet 1 7 INVENTOR cJammffli/i zn ATTORNE;

Dec. 23, 1941. s RUBEN 2,266,811

DIELECTRIC FOR ELECTROSTATIC CONDENSERS AND THE LIKE Filed Sept. 19, 1939 2 Sheets-Sheet 2 'INVENTOR ATTORNEY gamuel Fuen Patented Dec. 23, 1941 UNITED STATES PATENT OFFICE DIELECTRIC FOB ELECTROSTATIC CONDENSERS AND THE LIKE Samuel Ruben, New Rochelle, N. Y. Application September 19, 1939, Serial No. 295,581

6 Claims.

This invention relates to a dielectric material for electrostatic condensers and the like. The application is a continuation in part of my copending applications Serial No. 220,061, filed July 19, 1938; Serial No. 261,501, filed March 13, 1939; Serial No. 279,824, filed June 19, 1939, and Serial No. 285,891, filed July 22, 1 939.

The general object of the invention is the provision of a new and improved dielectric in solid, plastic or viscous form capable of continuous operation incapacitors for alternating and direct current operation.

The improved dielectric material comprises an hydrogenated wood resin combined with a solid halogenated dielectric plasticizer to produce a stable thermoplastic thermoadhesive composition.

In the drawings:

Figure 1 is an end view of a condenser section or unit in the process of winding;

Figure 2 is a longitudinal section through a completed capacitor;

Figure 3 consists of curves showing the power factor temperature characteristics of the dielectric material of the present invention compared with conventional dielectrics of the .prior art and present art, and also shows temperature-capacity and temperature-voltage breakdown characteristics of condensers employing the dielectric of this invention.

Rosin has been heretofore used in electrostatic condensers,.not as a dielectric but as an antioxidant for mineral oil, the amount of rosin used being in the order of Oxygen combines with rosin in preference to the mineral oil inwhich therosin is dissolved and the mineral oil is thereby protected. As a dielectric, rosin is undesirable because of its many inherent limitations such as brittleness, low voltage breakdown, in-

crease of power factor with temperature and.

because of the presence of unsaturated rosin acids. Also it is chemically unstable under electrical field conditions. It is subject to oxidation and due to its viscous gummy character even when heated does not satisfactorily impregnate wound foil type condensers. Its low voltage breakdown especially under continuous alternating current operation is a major disadvantage.

I have found that rosin, stabilized by hydrogenation to saturate the unsaturated acid bonds possesses characteristics which permit ts use in electrostatic condensers when combined with another dielectric, such as chlorinated naphthalene. The hydrogenation of, rosin eliminates the problem of oxidation and makes the rosin itseli useful as a dielectric although-this in turn detracts from its value as an oxidizing agent in mineral oil dielectrics.

Other hydrogenated wood resins such as hydrogenated turpentine can also be used. Turpentine, an olco-resin,-in some instances derived from the same source as rosin, is entirely unsuited as a dielectric because of its chemical and physical character. When polymerized, then hydrogenated to a clear white resin, however, it possesses properties similar to hydrogenated rosin though of a somewhat lower power factor.

In both cases the hydrogenation may be accomplished by a process in which the resins are heated to a temperature in the order of 200 C. under a pressure of 1000 pounds of hydrogen in the presence of a catalyzer for several hours, the time and pressure being dependent upon the degree of polymerization of the resin and the desired extent of hydrogenation.

In preparing the dielectric composition of this invention the hydrogenated rosin is combined with a solid halogenated dielectric such as solid chlorinated naphthalene, the two materials being heated and thoroughly mixed together at a temperature of C. While chlorinated naphthalene is the preferred added dielectric, other halogenated dielectrics such as solid chlor ethyl benzene, solid chlorinated iso propyl benzene or solid chlorinated di phenyl will also combine with the hydrogenated rosin. The addition of solid chlorinated naphthalene to the hydrogenated rosin softens the rosin, according to the proportion used, the hardness ra ging from a slightly deformable plastic material to that of a heavy viscid composition. I have found that about 30% by weight of chlorinated naphthalene is the maximum that can be combined with the hydrogenated rosin to form a clear homogeneous material. When the proportion is kept below 30% the combined dielectric is a clear amber colored material possessing new characteristics difierent from those of either the hydrogenated rosin or the chlorinated naphthalene. Its power factor characteristic is opposite to that of chlorinated naphthalene which rapidly increases with temperature rise. In the dielectric of this invention there is a decreasing power factor with temperature rise within the operating ranges of electrical equipment.

Chlorinated naphthalene'by itself has never been usable on alternating current due to various reasons, such as its instability, crystalline character, porosity and poor moisture resistance. These defects are eliminated when the chlorinated naphthalene is combined with the resin I I such as hydrogenated rosin an d a compound is obtained which is water proof, non-inflammable, capable of operating on continuous alternating current and which possesses a good dielectric constant. Where substantially more than 30% of the chlorinated naphthalene is used, there is some precipitation of the chlorinated naphthalene, an emulsion type mixture being obtained at room temperature, instead of a homogeneous, light colored, clear resin, with apparently an excess of uncombined or undissolved chlorinated naphthalene.

The chlorinated naphthalene-resins have a lower melting point than the resins alone and a lower hot viscosity, according to the amount of chlorinated naphthalene combined and as a result, the impregnation of paper-spacer electrostatic condensers is more satisfactory and complete.

The preferred percentage of solid chlorinated naphthalene to be added to the resin is from about to 30%, although for some applications such as .for dielectric potting compositions,

the percentage of chlorinated naphthalene may be considerably higher. For use as a dielectric in foil-spacer wound electrostatic condensers I prefer to keep the proportion of chlorinated naphthalene just under 30%. This composition will .not too readily flow at temperatures up to approximately 50 C. and .has a reducing power factor characteristic with temperature latter property is of major importance in'non-liquid type alternating current electrostatic condensers because it prevents the rise in power factor due to the poor heat conductivity inherent in immobile dielectrics and gives the equivalent of a circulating dielectric of low power factor. The dielectrics of this invention, due to the immobilization of. any ionic conduction elements or cataphoric conduction which occurs when liquid diperatures.

It will be observed from the line marked "capacity that over a temperature range of 20 C. to 90 C. the capacitance remains substantially constant.

One of the major causes of .breakdown of condensers used with capacitor motors, especially where the condenser is mounted within the motor frame, is the positive coeflicient of'power factor with temperature of the condenser dielectric. The dielectric breaks down due to progressive increase of power factor and temperature which tends to lower the dielectric strength. In direct contrast with this, the dielectrics of this invention have decreasing power factor with increasing temperatures, especially at temperatures experienced in small motors such as up to 60 C. The lowering of this power factor'introduces a protective factor, allowing operation over a considerably longer period than has been possible with present and prior art dielectrics.

The condensers can be produced in any wellknown manner, as shown in Figure l, for exam- .ple; bywinding together interleaved metal ,foils II and i2 andspacers l3 and H of paper, plasspacers of two 01 more-layers.

ticizer-free'regenerated sheet cellulose and the like or combinations of these to form composite After winding the condensersinto sections or units 1 they are impregnated by immersing them in the molten dielectric material of the presentinv'ention.

Figure 2 shows a completed condenser comprisingunitor section I impregnated with the dielectriciof the present invention. The unit' -is contained ina fibre container I and preferelectrics are used withporous spacers, have extremely high resistivity.

-ln Figure 3 of the drawings is shown a'series I .of curves giving the temperature power-"factor;

nated dielectrics of chlorinated di-phenyl and castor oil. It will be noted that the power factor of condensers employing the dielectric of this invention'decreases' within the operating range of electrical motor equipmentflshe power factor being at its lowest point at about the maximum hydrogenated ably embedded in a sealing compound 8 which may, if desired, be of the same composition as the impregnating dielectric of the condenser unit. End disc 2 of the fibre container has terminals 3 and} riveted thereto and connected respectively to electrode foils II and of the condenser unit bymeans -of clamping contactors 5 and 6 respectively,

. 1 Generally inv the manufacture of condensers, the method and processdescribed in my copend- ,ing application Serial No, 285,891, above referred to, may be followed.

'What'is claimed is:

l. A dielectric comprising hydrogenated tree resin and solid chlorinated naphthalene.

-motor operating temperatures; ,whereasthe' power factor of the other condensers commences 35 C. (chlorinated'di-phenyl);

I Also shown on Figure. 3 is a curve giving breakj-i down voltageswith-temperature of .wound foil mil paper spacers condensers employing two .38

-impregnated with 7-0 resin. 7 It will be-seen that the voltage breakdown values remain. ex-

7 ceptionally high even at very elevated temperatures. 1 Another highly desirable characteristic of con-.

" to sharply rise at 20 (forcastor'oil) n 2. A dielectric composition comprising solid hydrogenated tree resin in a preponderating amount and solid-chlorinated naphthalene.

3. A dielectric for electrostatic condensers and the like comprising essentially a mixture of solid hydrogenated tree resin and chlorinated naphthalene.

4. A dielectric for electrical devices comprising essentially a hydrogenated tree resin and a solid f halogenated dielectric.

I6. An-electric capacitor comprising armatures, porous dielectric material therebetween and an impregnant for said material consisting essentially of polymerized hydrogenated rosin and solid chlorinated naphthalene.

. SAMUEL RUBEN.

5; An I e'ctric capacitor having-,armatures; and

a dielectric material 'eonsistin'g toea -sub'stantialf' extent at least of, polymerized hydrogenated tree resin and solid chlorinated naphthalene.

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