Polyester fiber-vacuum impregnated epoxy resin insulation system for high voltage transformers

• US 3,979,530 A
• Filed: 04/15/1974
• Issued: 09/07/1976
• Est. Priority Date: 04/15/1974
• Status: Expired due to Term

• Current Assignee: Hughes Aircraft Company (Rtx Corporation)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Burnham, John, Buritz, Robert S., Schwider, Alfred W.
• Primary Examiner(s): Welsh, John D.
• Application Number:
  US05/461,071
• Time in Patent Office: 876 Days
• Field of Search: 252/65, 252/640, 252/63.2, 174/110 E, 174/110 SR, 174/127, 161/169, 161/170, 260/37 EP, 427/294, 427/296, 427/104, 427/203, 427/206
• US Class Current: 427/104
• CPC Class Codes: H01B 3/40 epoxy resins
• CPC Class Codes: H01B 3/485 Other fibrous materials fabric
• CPC Class Codes: H01F 27/327 Encapsulating or impregnating encapsulating coil and core H01F27/022
• CPC Class Codes: H02K 15/12 Impregnating, heating or drying of windings, stators, rotors or machines
• CPC Class Codes: Y10S 264/54 Processes in making insulators
• CPC Class Codes: Y10S 264/75 Processes of uniting two or more fibers
• CPC Class Codes: Y10T 428/31515 As intermediate layer
• CPC Class Codes: Y10T 428/31786 Of polyester [e.g., alkyd, etc.]

Abstract

A new insulation system, useful for the fabrication of high voltage transformers, capacitors and power supply encapsulation and insulation for high voltage leads, has been developed which substantially eliminates corona and improves reliability of these devices.

Claims

1. A process for making a polyester-filled epoxy resin electrical insulation system comprised of epoxy-impregnated chopped polyester fibers which includes the steps of applying a porous fiber mat to an electrical device to be insulated, vacuum baking said fibers at 100 to 110°

C for at least 16 hours and then placing said device into a suitable impregnation container heated to 90°

to 110°

C, wherein said impregnation chamber is evacuated to a pressure of 30 μ

Hg or less, said epoxy resin is heated to 75°

±

5°

C and degassed at a pressure of 700 μ

Hg or less prior to addition of a nonstoichiometric hardener, comprised of a mixture of menthane diamine, metaphenylene diamine, and benzyldimethylamine, said hardener is added to said resin at 75 ±

5°

C mixed thoroughly and degassed thereby forming a curable resin system, said resin system is introduced into said impregnation chamber whereby all fibers to be impregnated are completely covered by said resin system, said impregnated fibers are removed from said

2. A process for making an electrical insulation system composed of a porous barrier material and a curable resin comprising the steps of

a. applying said porous barrier material to an electrical device and prebaking said material at an elevated temperature of from 100°

to 110°

C for a period of not less than 16 hours at a reduced atmospheric pressure,

b. maintaining said elevated temperature while evacuating a chamber contaning said material to a pressure of less than 30 microns of mercury,

c. introducing a hot degassed resin premix into said chamber until said baked material is completely submerged in said resin, thereby causing said porous material to be impregnated with said resin,

d. pressurizing said impregnated material with dry nitrogen to at least 500 psi and maintaining said material at this pressure and at a temperature of from 70°

to 80°

C for a period not less than 16 hours, and

e. returning said material to ambient pressures to cure said material at a temperature of from 125°

to 130°

C prior to allowing said material to cool.

3. The process of claim 2 where said resin is a reaction product of bisphenol-A and epichlorohydrin cured with a hardener comprised of menthane diamine, metaphenylene diamine, and benzyldimethylamine in a nonstoichiometric ratio.