Browse Prior Art Database

EMC Design of an Electronic Processing System Mounted in a Standard EIA Rack

IP.com Disclosure Number: IPCOM000036377D
Original Publication Date: 1989-Sep-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Crippen, MJ: AUTHOR [+3]

Abstract

The rack-mounted electronic processing system described here consists of several electronic drawers connected together and mounted in an EIA rack. Each drawer consists of logic cards and boards, cooling devices, power supplies, connector assemblies and associated cables (Fig. 1).

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EMC Design of an Electronic Processing System Mounted in a Standard EIA Rack

The rack-mounted electronic processing system described here consists of several electronic drawers connected together and mounted in an EIA rack. Each drawer consists of logic cards and boards, cooling devices, power supplies, connector assemblies and associated cables (Fig. 1).

Conventional EIA rack designs provide little protection for radiated EMI (Electromagnetic Interference) and virtually no protection for ESD (Electrostatic Discharge). As a result, each electronic drawer must be designed to provide its own protection.

EMI shielding is provided by completely shielding each electronic drawer in a metal chassis. The metal chassis has a highly conductive surface coating to provide a good EMC ground. A good EMC ground is defined as one having a resistance of 10 milliohms or less measured with a standard 4 terminal milliohmeter. The drawer has sufficient surface area to ensure the 10 milliohm ground to the front and back mounting rails of the EIA rack (Fig. 2). The drawers are fastened to the rack by standard fasteners and are torqued to specified values.

The openings in the drawer which are necessary for air cooling are shielded with a screen having a maximum dimension of 6 mm by 6 mm

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and grounded to the chassis along its perimeter. The geometry of the openings is not important.

Cables entering the drawers are shielded. The shields are terminated in a 360-degree clamp...