US1223881A - Electrical insulation. - Google Patents

Description

W. A. ISHLER.

ELECTRICAL INSULATION.

APPLICATION FILED SEPT. 11. 1916.

Patented Apr. 24, 1917.

lnverwtorz Willisfllshler;

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EIQEGTRTG GtlMPANY, [a

l. 23,$8ll. Specification o Application filed September ing eflects of high frequency and which are of general application to various types of apparatus.

It has been discovered that films or layers of insulating oils, at least of such oils as are now commonly used for submerging electrical apparatus, are particularly capable of maintaining high insulating characteristics under the high frequencies to which some electrical apparatus, particularly transformers, are occasionally subjected. Other common insulating materials and structures .are liable to unexpected failures under the application of high frequencies. By my invention T secure in insulating barriers or pads the advantages of this property of oil, as well as its better known insulating properties, by employing totally inclosed impervious casings containing oil as in the form of films or layers, preferably in the form of sheets of oil soaked fibrous material. At one or both sides of the oil layer may be applied one or more thicknesses of other insulating materials as conditions may dictate, for example to render the whole barrier more or less fireproof- A structure of this kind may be made in; the form of a fairly flexible pad which may be wrapped around the part to be insulated-thereby. Such a structure is self contained and is protected against modification by outside influences. The oil thereof cannot be displaced .nor absorbmoisture or other foreign fluids and thereby the pad lose its expected strength. The pad may therefore be ap- Better: Pate Patented Apr. 2 ft, third.

eral application, that is, is applicable both to devices submerged in oil and to those not submerged in oil, such as, for example, air blast transformers; in both cases the enveloping casing retains the oil of the insulating structure in its original quantity and purity. It. is even possible therefore by employing my invention to obtain some of the advantages of oil insulation in apparatus not submerged in oil.

in the accompanying drawing and the following detailed description I have illustrated and described the best embodiment of my invention that T am nowaware of, and such as T have found after a long course of tests, to possess very desirable characteristics. Figure l is an elevation of an insulating barrier or pad embodying my invention such as is suitable for use between the primary and secondary windings of small transformers. Figs. 2 and 3 are sections thereof respectively "on the lines 2-2 and 33 of Fig. 1. Fig. 4 is a perspective of the pad of Fig. l in substantially the form it assumes in the transformer of Fig. 5. Fig. 5 is a plan view of a transformer provided with pads such as are illustrated in the preceding figures.

The pad of the drawing is made up of a number of layers of different insulating materials. The center layer 10 comprises a sheet of blotting paper thoroughly soaked or saturated with insulating oil, for example such oil as is now used for submerging transformers. At each side of this sheet of oil soaked blotting paper is a sheet ll of pastedrnica (that is, scraps of mica film pasted together into the form of a sheet and thoroughly compressed) between thicknesses of paper. Totally inclosingthese sheets of insulating materials is a wrapping 12 of varnished cambric which is impervious to most fluids.

In applying the impervious wrapping of varnished cambric to produce the pad illustrated in the drawing, the oil soaked blotting paper and the mica and paper sheets are assembled upon substantially the center of a sheet of varnished cambric cut to the, requisite size. ()ne edge, for example the near edge of the varnished cambric, is then folded over the top mica sheet to the position indicated by the dotted line 15 of Fig; 1. The opposite or far edge of the cambric is likewise folded, but in the opposite direcarethen folded over and thoroughly stuck together, for example in the manner illustrated in Fig. 2. The overlapping edges may be shellacked to form tight joints. This manner of folding the varnished cambric produces a totally inclosed impervious case or'wrapping.

As this pad is applied to the transformer of Fig. 5, it assumes a shape something like that illustrated in perspective Fig. 4." In Fig. 5 two such pads are shown in position in a transformer. The windings of this transformer surround the middle leg of the core 20. The windings comprise two low potential windings 21 and 22 and a hugh potential winding of two coils 23 and 24 between the two low potential windings. Ventilating spaces 25 are left between the low potential winding 21 and the high potential winding, and likewise an annular ventilating space 26 is leftbetween the two coils 23 and 24: of the high potential winding. After'the low potential winding 22 is applied to the core. a barrier or pad 30, such as has .been described hereinbefore, is wrapped around the same and over this is placed the high potential winding. On the outside of the high potential winding is likewise placed a similar barrier or pad 31.

and the low potential winding 21 is placed outside this barrier. Such a transformer may safely be impregnated with insulating materials after assembly as is\now a common practice, for the totally inclosing impervious wrapping thoroughly excludes the impregnating material from the'absorbent sheet of the pad and retains the oil thereof. Short circuits even 010% to the pad, cannot entirely destroy the insulating properties of the pad due to the fire resisting qualities of the mica sheets. As will be apwhether the transformer of Fig. 5 is submerged in oil or not during operation, some of the advantages of oil insulation are secured between the primary and secondary windings. 1

While I have described the principleof my invention and the 'best mode I have contemplated for applying this principle, other modifications will occur to those skilled in this art and I aim in the appended claims to cover all modifications which do not involve a departure from the spirit and scope of my invention.

a What I claim as new and desire to secure by Letters Patent of the United States, is,

1- An insulation barrier comprising a relaatively thin totally inclosed casing of an insulating material impervious to oil and a film of oil contained therein.

2. An insulating barrier comprising a relatively thin impervious totally inclosed casing and oil therein.

3. An' insulating barrier comprising an oil soaked absorbent sheet and an impervious wrapping totally inclosing the same.

4. An insulating 'barriercomprising an oil soaked absorbent sheet, a sheet of fire resistant material at each side thereof and an impervious wrapping totally inclosing the same.

5. An insulating barrier comprising an oil soaked absorbent sheet, a sheet of insulating material at one sidethereof and an impervious wrapping totally inclosing the same.

In witness whereof, I have hereunto set my hand this 24th day of Aug. 1916.

WILLIS ALDEN ISHLER.

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