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Low Modulus Encapsulation System

IP.com Disclosure Number: IPCOM000089995D
Original Publication Date: 1969-Jan-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Braune, R: AUTHOR

Abstract

A low-modulus encapsulating formulation for electrical devices prevents insulation squeeze-out and possible shorting of electrical coils. In a unit such as a magnetic amplifier, adjacent turns of several coils are covered with an insulating coating such as polyurethane. If, for example, the amplifier is encapsulated with a conventional epoxy resin formulation, failure can occur after some period of time. The relatively high-modulus epoxy resin exhibits high-shrinkage stress, forcing certain adjacent turns together and causing the insulation to neck down until resistance shorting occurs. This problem is overcome by replacing the high-modulus encapsulating formulation with a low-modulus, flexible material such as an elastomeric polyurethane resin.

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Low Modulus Encapsulation System

A low-modulus encapsulating formulation for electrical devices prevents insulation squeeze-out and possible shorting of electrical coils. In a unit such as a magnetic amplifier, adjacent turns of several coils are covered with an insulating coating such as polyurethane. If, for example, the amplifier is encapsulated with a conventional epoxy resin formulation, failure can occur after some period of time. The relatively high-modulus epoxy resin exhibits high-shrinkage stress, forcing certain adjacent turns together and causing the insulation to neck down until resistance shorting occurs.

This problem is overcome by replacing the high-modulus encapsulating formulation with a low-modulus, flexible material such as an elastomeric polyurethane resin. During operation of the amplifier, the polyurethane resin encapsulant does not create sufficient stress upon the turns to cause shorting. In addition, glass type washers are placed between certain turns to further relieve the stress upon the insulating coating.

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