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Electrical apparatus encapsulant

a technology of encapsulant and electrical winding, which is applied in the direction of inhomogeneous insulation materials, transportation and packaging, coatings, etc., can solve the problems of limited thermal stability of encapsulant materials, restricted operating temperature of electrical machines, and chemical and physical compatibility of encapsulant compositions used to mechanically encapsulate electrical windings of high temperature electrical machines. , to achieve the effect of improving the thermal conductivity of encapsulant compositions, increasing the thermal coefficien

Inactive Publication Date: 2014-11-20
ROLLS ROYCE PLC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The invention provides an electrical encapsulant with good thermal stability, mechanical strength, and dielectric strength. It is compatible with high temperature wire insulation materials and can be used for a wide range of applications. The encapsulant has a low volume shrinkage and its organic component provides high strength when cured. The refractory ceramics particles in the encapsulant improve its compatibility with wire insulation materials and also enhance its mechanical strength. The metallic particles in the matrix increase its thermal conductivity and can be controlled to match the thermal expansion of the wire insulation material. The addition of fibres increases the mechanical strength of the resulting composition.

Problems solved by technology

For example, encapsulant compositions used to mechanically encapsulate electrical windings of high temperature electrical machines are subject to particularly harsh thermal and mechanical conditions.
A major barrier restricting the operating temperature of electrical machines is the limited thermal stability of the encapsulant material.
Breakdown of encapsulant materials can occur at excessively high temperatures, or following prolonged exposure to high temperatures.
Such breakdown may lead to mechanical or electrical failure of the electrical machine.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0053]A first electrical encapsulant composition comprising a silica containing inorganic-organic nano-hybrid matrix, and particles of refractory ceramics suspended in the inorganic-organic nano-hybrid matrix is produced as follows.

[0054]Silicon containing Methyltrimethoxysilane 40.8 g is charged in a flask. Dilute hydrochloric acid (HCl, 1N concentration) 5.4 g is added drop by drop to this mixture under vigorous stirring. After addition of hydrochloric acid solution, the reaction mixture is heated to reflux for 6 hours and followed by distilling out the by-product, methanol. The nano-hybrid resin thus synthesised is of the structures I and II (see FIG. 1) with a proper fraction of OR′ groups remaining in the molecules because insufficient water is available for hydrolysing all OR′ groups in the example. These OR′ groups have been found to keep the resin in liquid form, and are relatively stable at room temperature. The OR′ groups may be subject to further hydrolysis / condensation w...

example 2

[0057]In example 1, the non-hydrolysable R group is methyl, which remains in the resin after curing. In example 2, a phenyl group is introduced into the nano-hybrid resin.

[0058]A second electrical encapsulant composition can be formed as follows. Methyltrimethoxysilane 32.6 g and phenyltriethoxysilane are mixed in a flask. 5.94 g HCl solution is dropped into the mixture under vigorous stirring. After addition of HCl solution, the reaction is kept refluxing for 12 hours and then the by-products, methanol and ethanol, are driven out by distillation. A clear viscous resin is thus produced.

[0059]In other syntheses, the molar ratio of methyl to phenyl can vary in the range from 30 / 70 to 98 / 2. Increase of phenyl group leads to increase of thermal stability and thermal expansion coefficient of the cured nano-hybrid resins.

[0060]Again, the amount of HCl solution and the refluxing time may also be changed to adjust the properties of resultant nano-hybrid resins.

example 3

[0061]A third electrical encapsulant composition can be formed as follows.

[0062]Methyltrimethoxysilane 32.6 g, trimethylmethoxysilane 6.2 g, vinyltriethoxysilane 2.8 g and triethoxysilane 2.5 g are mixed in a flask. Phosphoric acid 0.75 g is dissolved in water 10.8 g and the acidic water is added drop by drop into the above mixture under vigorous stirring at room temperature. Afterwards, the reaction system is heated to refluxing and kept at this condition for 20 hours. Then the by-products, methanol and ethanol, are distilled out by gradually raising the temperature to 100° C. The clear nano-hybrid resin in liquid form is then obtained and ready for compounding.

[0063]The resultant nano-hybrid resin may be cured by the addition reaction between Si—H vinyl group in the presence of appropriate catalysts, e.g. platinum.

[0064]The ratio of methyltrimetoxysilane to trimethylmethoxysilane can be varied to adjust the viscosity of the resultant resins, with a higher ratio leading to higher v...

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Abstract

An encapsulant composition has a silica containing inorganic-organic nano-hybrid matrix, particles of refractory ceramics suspended in the inorganic-organic nano-hybrid matrix, and, optionally, glass or ceramic fibres. The encapsulant may also contain ceramic coated metallic particles, and in some embodiments, a solvent or binder. The formulations can include a solvent, which may be removed during a curing process, or may be solvent-less

Description

FIELD OF THE INVENTION[0001]The present invention relates to an electrical apparatus encapsulant, particularly though not exclusively to an electrical encapsulant for a high temperature electrical machine, and an electrical machine comprising the encapsulant.BACKGROUND TO THE INVENTION[0002]The development of electrical apparatus such as electrical machines for use in high temperature environments places significant demands on components associated with the apparatus. In particular, there is a requirement for stability of the materials from which the components are constructed. Such machines generally comprise electrical windings embedded in an electrical encapsulant, sometimes also known as an impregnant. Such encapsulants provide mechanical stability and secondary electrical insulation of the electrical windings in addition to that provided by the insulating material surrounding the wires of the coil. Environments requiring stability of electrical encapsulants at high temperature ...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C09D183/06
CPCC09D183/06H01B3/002Y10T428/31663H01F5/06
Inventor BRUCE, GRAHAM PHILIPCULLEN, JOHN JAMES ANTHONYHUSBAND, STEPHEN MARKPANG, YONGXINHODGSON, SIMON
Owner ROLLS ROYCE PLC
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