US2235566A - Electrostatic condenser - Google Patents

Description

March 18, 1941- s. RUBEN ELECTROSTATIC CONDENSER Filed July 21, 1939 2 Sheets-Sheet l INVENTOR damuei fium/ ATTORNEY 2 Sheets-Sheet 2 March 18, 1941. s. RUBEN ELECTROSTATIC CONDENSER Filed July '21, 1939 Ul/HbJOIJ/N 6/94! "#095711! :TJNb'lQ/SJ Patented Mar. 18, 1941 UNITED STATES PATENT OFFICE v 7 Claims.

This invention relates to electrostatic condensers and particularly to such condensers employing liquid hydrocarbon dielectrics. This application is a continuation in part of my copending applications Serial No. 248,619, filed December 30, 1938, entitled Condenser dielectric," application Serial No. 279,824, filed June 19, 1939, en-

titled Electrostatic condenser and dielectric therefor, which application was a continua- 10 tion in part of my prior application Serial No.

235,543, filed October 18, 1938. entitled Electrostatic condenser.

The general object of the invention is the provision of an electrostatic condenser employing a stable liquid dielectric superior in electrical characteristics to other types of liquid dielectrics previously used.

A specific object is the provision of a condenser of the liquid dielectric type having a lower power factor than condensers of similar type previously used.

A further specific object is the provision of a condenser of the liquid dielectric type in which the power factor remains constant or slightly decreases over the entire operating temperature range of the condenser.

Another object is the provision of a condenser of the liquid dielectric type in which the capacitance of the condenser remains substantially constant over the entire operating temperature range of the condensers.

Still another object is the provision of a liquid dielectric condenser capable of advantageously replacing condensers of the air, gas and mica dielectric type.

Other objects will be apparent as the disclosure proceeds and from the drawings in which Fig. 1 is an end view of a partly assembled condenser; Fig. 2 is a section through a completed condenser and Fig. 3 is a graph containing groups of curves showing power factor-temperature characteristics, and resistivity-temperature characteristics of condensers of this invention compared with condensers of the prior art and also illustrating the temperature-capacitance characteristics of condensers of this invention,

Heretofore, mineral oil has been almost exclusively used as the dielectric in liquid hydrocarbon dielectric condensers. However, it possesses several disadvantages, for example, being composed of many compounds, it is subject to the eflect of electrical fields, especially if of high tension and at high temperature. After a period of operation, a wax-like sludge is formed and there is a sensitivity to oxidation. To reduce the oxidation, it has been necessary to add to the mineral oil more readily oxidizable materials, such as abietic acid, which is usually present in mineral oil condensers to the extent of 10%. Other limitations to the use of mineral oil condensers are 5 the increase of power factor and large decrease in resistance with temperature.

The power factor loss of condensers employing porous spacers such as kraft condenser paper is doubled when the condenser is impregnated with 10 mineral oil. In addition, the mineral oil can hold moisture in suspension which, under the applied electric field, tends to localize and exhibit electrolytic eifects when the condenser is operated above a critical value, especially at elevated temperatures. Another v disadvantage is that the losses at high frequencies are considerably greater with mineral oil than at the lower frequencies.

The present invention comprises the use of the dimer of di-hydronapthalene (CzoHzo) as the di- 20 electric in electrostatic condensers. I have found that this compound approaches the ideal dielectric for liquid type capacitors. It has a power factor loss lower than styrene, it is notably good for high frequency applications and it is of suih- 25 ciently high vapor pressure to allow complete impregnation under reduced pressure. Its pour point is about 10 C., it decomposes at about 350 C. to 400 C., it has a boiling point of 200 C. at 1 mm. and a refractive index of 1.6 at 24 C. The 30 compound is stable and resistant to oxidation so that it may be used alone. Its stability and excellent dielectric properties are probably due to its single compound nature and to the stable molecular structure obtained by the saturation of the 35 conjugated ring structure of its monomer, ClOHlO. Other liquid hydrogenated naphthalenes, such as deca hydronaphthalene and tetra hydronaphthalene are unsuitable as condenser dielectrics because of their volatility, especially under the low 40 pressures necessary for vacuum impregnation. Furthermore, they are comparatively unstable, do not possess the low power factor or dielectric strength of them-hydronaphthalene dimer and are readily inflammable. i5

Kraft paper condensers impregnated with the dl-hydronaphthalene dimer show a power factor of 0.18% compared with 0.15% prior to impregnatlon; whereas the power factor of mineral oil impregnated condensers is 0.3%, chlorinated di- 50 phenyl impregnated condensers 0.3% and castor oil impregnated condensers 0.5%. Where linen paper spacer condensers are impregnated with the dimer of di-hydronaphthalene. the impregnated power factor is only 0.1%. 5

Gil.

with dimer of di-hydronaphthalene.

The exceptional stability, low power factor and other desirable electrical characteristics of the dimer of di-hydronaphthalene as compared with other dielectrics are shown by the curves in Fig. 3; based on condensers employing two .4 mil kraft paper separators between foils. It will be noted that in the temperature rise from C. to 70 C., the power factor at 60-cycles of the mineral oil (containing 10% abietic acid), chlorinated diphenyl and castor oil dielectrics rises to many times their initial values while the CroHzo impregnated condenser showed an actual decrease in power factor from 0.18% to 0.165%. The power factor, if linen paper instead of kraft paper separators were used, would be still lower, as indicated by the small circleon the graph designated linen.

It will be noted from Fig. 3 that the resistivity of the CzoHzo impregnated condensers is considerably higher than that of the other three liquid dielectrics. The graph also shows the constant capacitance characteristics of the C2oH2o at room temperature up to 80 C.

Figs. 1 and 2 illustrate the type of condenser from the operation of which, the curves in Fig. 3 were plotted.

Fig, 1 is an end view of a condenser section, l0, comprising two foil electrodes II and I2 of aluminum or other suitable metallic foil, wound together with double spacers I3 and M of kraft paper.

Fig. 2 shows a completed capacitor embodying condenser section Ill illustrated in Fig. 2, mounted within aluminum container 3| and impregnated The leads 33 and 34 are soldered to terminals 35 and 36 and extend through top 39. Soft chlorinated rubber plug 4| holds the condenser section in place. The top of the condenser is spun over against chlorinated rubber washer 40 in order to afford a tight seal. The condenser may be filled with C20H20 through the hole sealed by plug 42.

If desired, processed regenerated sheet cellulose of the type described in my copendingapplication Serial No. 256,668, can be substituted for the paper or a composite spacer of regenerated sheet cellulose and paper can be used.

While the condensers described have been of the wound foil-spacer type, the characteristics of the CzoHzo, such as constant low power factor, low loss at high frequencies and constant capacitance with increase in temperature, make the dielectric also especially useful in condensers having fixed spacing means at the ends of the electrodes, for example in structures used for air or gas dielectric type condensers. The substitution of the dielectric of this invention would provide lower power factors and where radio frequencies are applied, would allow several times the capacitance and a higher voltage for a given space than the air type condensers. This is of vital importance in condensers for high voltage and high frequency generators and for high tension transmission line condensers.

While for most condensers the CaoHzo may be used alone, it may also be combined with other dielectrics, such as the tetramer of di-hydronaphthalene, hydrogenated polymerized indene,

etc. (as mentioned in my copending application Serial No. 279,824), chlorinated naphthalene, chlorinated di-phenyl, mineral, oil, castor oil, hydrogenated castor oil, styrene, nitro benzene, etc.

The compound may also be halogenated, pref- .erably by chlorination, where a non-inflammable dielectric is desired. The material so produced may be used as a cooling dielectric in transformers and other electrical apparatus.

What is claimed is:

1. An electric capacitor having armatures and a dielectric material consisting to a substantial extentat least of dimer of di-hydronaphthalene.

2. An electric capacitor comprising armatures, porous dielectric material therebetween and an impregnant for said material consisting essentially of dimer of di-hydronaphthalene.

8. An electric capacitor having cooperating armatures and containing dielectric material consisting preponderantly of dimer of di-hydronaphthalene.

4. An electric capacitor having cooperating armatures and containing dielectric material consisting preponderantly of halogenated dimer of di-hydronaphthalene.

5. An electric capacitor comprising armatures and one or more layers of flexible sheet cellulose therebetween and an impregnant therefor comprising dimer of di-hydronaphthalene as a substantial and essential ingredient.

6. An electric capacitor comprising armatures and one or more layers of regenerated sheet cellulose therebetween and an impregnant between said armatures consisting to a substantial extent at least of dimer of di-hydronaphthalene.

7. An electric capacitor having armatures and a dielectric material consisting to a substantial extent at least of dimer of di-hydronaphthalene and another dielectric compound miscible therewith.

SAMUEL RUBEN.

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