By Robin Jeffery, Technical Market Analyst at TDK-Lambda EMEA
Electromagnetic compatibility (EMC) defines the ability of electrical and electronic equipment to operate acceptably when exposed to external electromagnetic sources and limiting internally generating unwanted electromagnetic energy. EMC covers three areas. Limiting emissions generated by the equipment, its susceptibility to external sources and its level of immunity when functioning in its defined environment.
To begin with, EMC caused a large number of issues across a great number of industries and applications. Back in the early 1990s one of the most severe incidents of interruption of an auto pilot system by passenger electronics was from a portable CD player (1). Anyone who has flown will have been asked to put their mobile phone into flight mode. Rail network operators too have recorded numerous events due to electric trains causing issues with trackside signalling.
Since then, laws and standards have been introduced to address EMC but they vary by country. In the European Union (EU) manufacturers of electronic equipment have to state their compliance by labelling their product with the CE Mark to the EU Directive 2004/108/EC. A series of additional standards applies depending on the end application.
For power supplies EN 55011, EN 55032 and EN 61000 are the most widely used standards used, which cover emissions and immunity. These in part refer to the standards of CISPR (International Special Committee on Radio Interference). In the US, FCC Part 15 is used to regulate “unlicensed” radio frequency (RF) transmissions. MIL-STD-461 is the US military standard for subsystems.
From an AC-DC medical power supply perspective, the manufacturer will be concerned about emissions and immunity. With the increasing amount of home healthcare devices operating out of the benign environment of a hospital, the medical standard EN60601-1-2 was recently tightened to reflect the severity of this.
For more information about EMC, please visit: www.emea.lambda.tdk.com/emc
- Taken from Compliance Engineering Spring 1993, page 92, itself commenting on an article in Time, Feb 22, 1993, www.ce-mag.com.