Page 121 - Power Electronics Handbook

114 Electromagnetic compatibility

c------.+ BSI conducted

c-------+ BSI radiated
FCC conducted

FCC radiated

MIL-STD conducted

MIL-STD radiated

I I I I I I I I I I I
10 100 1 10 100 1 10 100 1 10 100
HZ kHz MHz GHz
F~~wc Spectrum of frequencies covered by typical EMC standards
4.9
Figure 4.9 shows the spread of frequencies covered by a few typical
standards, as expected, the military operating over a much wider range
than the commercial. In order to ensure some commonality of standards
between different countries the IEC (International Electrotechnical
Commission) set up a subcommittee in 1934, called the CISPR
(International Special Committee on Radio Interference), to prepare
guidelines on EMC. These are now followed by most countries.
The European Communities EMC Directive 89/336/EEC, states that
apparatus covered by its scope must be such that the interference generated
does not prevent other radio or telecommunications equipment from
operating within its specification, and that the apparatus has sufficient
immunity from external interference so that it can operate as originally
intended (Brenda, 1995; Hicks, 1995; Ridley, 1995; Shavarooghi, 1995).
This Directive came fully into force on 1 January 1996 and it is now a
criminal offence to put onto the market any equipment which does not meet
its requirements.
Several standards have been developed and are being developed to support
these Directives, a few of these being given in Tables 4.1 to 4.3. Basic
standards are those produced within IEC loo0 and they give general
conditions for achieving EMC. serving as the reference documents for other
standards committees. Generic standards set down conditions for systems
operating in specified environments and product standards define the
requirements for specific product groups and how these can be tested.
As an example in the UK the BSI maintained BS 6527, which defined its
EMC requirements, although this has now been replaced by European
standard, EN55022, which was ratified by all CENELEC countries in June
1986, and is the system to which European countries are working. EN 55022
covers information technology equipment, i.e. receiving data equipment such
as data input lines and keyboards; processing data equipment, such as
computation and storage; and data output equipment. This standard grants