Important new development in Generic EMC standards

KNOW YOUR STANDARDS

by J. M. Woodgate B.Sc.(Eng.) C.Eng. MIET SMIEEE FAES Hon FInstSCE MIOA

Important new development in Generic EMC standards

Overview

CISPR/H, not one of the most innovative committees, attempted to add Class A limits to the Generic IEC 61000-6-3, but European (not UK) National Committees rejected the proposal. The issue stems from the very old CENELEC decision, taken at the time of writing the first Generics, to consider only two EMC environments, Residential, commercial and light industrial (RCLI) and [heavy] Industrial. This immediately brought the European and North American EMC regulations into conflict, because in North America, any equipment can be used anywhere, but if interference results, it has to be remedied.

This choice of only two environments came as a big surprise to the BSI Panel committee writing, well before the Generics were published, what eventually became EN 55103-1. The committee noted that eight environments were then defined in IEC 61000-2-5 and expected that a substantial number of these would be addressed in the Generics, so had no hesitation in addressing five environments in the draft for EN 55103-1.

At least twenty years ago, the originator of the 'two environments' concept acknowledged that it was an oversimplification and proposed four environments, taking into account whether the electricity supply was public or private, which affects the applicability of several IEC 61000-3 Sections. However, the grouping of R with CLI was not addressed, and the proposal was not followed up except in the Scope causes of the standards.

Consideration of Class A and Class B emission limits starts with the concept of protecting broadcast receivers (strictly CISPR considers only broadcast receivers, not other potential EMI victims) from interference by assuming a minimum 'separation distance' of emitter and receiver. For Class A, this is 30 m, while for Class B it is 10 m. This not only affects the limit values but also the distance between source and receiver in emission measurements. This is important because some measurements have to be done in the 'near field', the fuzzy-bordered region, with a radius about one-sixth of a wavelength of the emission frequency, around the source where the electric and magnetic field strengths are not related by the impedance of free space. Since the wavelength of a 10 MHz emission is about 30 m, the near field can be seen to be quite extensive over a very large frequency range.

The concept of 'separation distance' can be seen to be problematical in many situations:

a radio receiver in one house separated only by a wall from a TV in another house;
a mobile phone anywhere;
a computer, a printer and a radio receiver in the same room, with LED lighting for good measure.

National committee comments on the failed attempt show confusion between the reasons for the Class A and B concepts on the one hand and the public and private electricity supply concepts on the other. They are totally independent.

New initiative

CISPR/H has now issued a New Work proposal for a Generic emission standard IEC 61000-3-8, to apply to a restricted range of equipment for use in CLI when meeting Class A limits. The restrictions are:

the equipment is professional equipment (the proposed definition aligns with IEC 61000-3-2 but is formally defective);
the equipment is professionally installed (but the draft does not actually set out such requirements and how they could be enforced);
the equipment is not intended [by the manufacturer] for use in residential locations.

The draft includes examples of the relevant locations:

retail outlets, for example shops, supermarkets;
business premises, for example offices, banks, hotels, data centres;
areas of public entertainment, for example cinemas, public bars, dance halls;
places of worship, for example temples, churches, mosques, synagogues;
outdoor locations, for example petrol stations, car parks, amusement and sports centres;
general public locations, for example parks, amusement facilities, public offices;
hospitals, educational institutions, for example schools, universities, colleges;
public traffic area, railway stations, and public areas of an airport;
light-industrial locations, for example workshops, laboratories, service centres.

Curiously, the list is supplemented by a Note that says that radio receivers may be located within 30 m. It would appear more relevant to say that they are not expected to be located within 10 m. But of course, a portable radio can be anywhere.

The majority of the text is derived from IEC 61000-6-3 with only essential changes. There is an informative Annex which cites the product or product-family emission standards for various types or equipment and the corresponding immunity standards. These take precedence over the Generic, so they do not at present allow Class A except in [heavy] industrial locations. This raises the question of what equipment the proposed Generic can apply to? It seems that there is very little. The Generic may be the 'thin end of a wedge', prompting revisions of all the product standards to fall into line. This, if it happens at all, will take a long time.

It is notable that lighting equipment is not mentioned in the Annex. Lighting equipment covers:

lamps with no on-board electronics or dedicated electronic interfaces. The EMC environment is not relevant;
lamps with on-board electronics or dedicated or generic electronic interfaces. The EMC environment is relevant, and removal of restriction to Class B may be advantageous;
control equipment which is designated in standards (e.g. IEC 61000-3-2 and CISPR 15) as 'lighting equipment. The EMC environment is relevant, and removal of restriction to Class B may be advantageous;

The closing date for voting on the proposal is 8 June 2018, and the result may be known before IEC Central office goes into low-key in August.

If you support the New Work proposal in principle, please tell EMCIA, so that its BSI committee members are fully briefed on industry opinion.