By J. M. Woodgate B.Sc.(Eng.) C.Eng. MIET MIEEE FAES
There has been a great deal of standards activity in the last three months, so reports are necessarily somewhat brief, but I hope not incomplete.
Generic immunity standards IEC 61000-6-1 and -2
CDs (Committee Drafts for comment) have been issued for these standards, with an explanation of the changes. In IEC 61000-6-1, new material on EMC environments in IEC 61000-2-5 is taken into account by means of an extensive text in the Scope clause (not, one would think, the best place for it), along with an extended frequency range for radio frequency field immunity tests in IEC 61000-4-3. In addition, the repetition rate for the fast transient test signal is changed, as are some test levels, and testing for immunity to voltage dips and interruptions is extended to cover equipment with a rated current above 16 A per phase, according to IEC 61000-4-34. A new clause on measurement uncertainty is added, as well as an annex on guidance for product committees.
In spite of the long text on environments, it is not stated that residential, commercial and light industrial environments are normally supplied by a public low-voltage electricity supply, unlike many (heavy) industrial locations. The standard is now to be applied to equipment that is battery powered or is powered by a private, non-industrial supply.
The guidance annex, in both drafts, lists some of the immunity standards for more recondite EMC phenomena, to encourage product committees to include them in their immunity requirements. For only a few dollars more, no doubt. These standards are, in the IEC 61000-4 series, Sections 12, 16, 18, 19 and 31, the last two not yet published, although Section 19 is at the FDIS stage at the time of writing.
In IEC 61000-6-2, the (heavy) industrial environment is described, with several provisos which may create more uncertainty than clarity. It's rather surprising that both drafts refer normatively to CISPR 22, which is replaced by CISPR 32.
Product standards are supposed to maintain consistency with the Generics, so some of these changes will filter through.
Two reports have been circulated to national standard bodies, one on an EMC Working Party meeting and one on the future of the RTTE Directive. In the EMC Working Party meeting, it was said that the new EMC Directive will be published in 'spring or early summer 2014'. Don't hold your breath, but there is more on this in the Column in this issue. The demarcation between the EMC Directive and the Vehicle EMC Directive continues to be discussed, as do the ramifications of the Digital Dividend (which in some ways seems to pay out a negative sum).
A further knotted topic is what to do about controlling the EMC properties of cables. The Commission does not at present see cables as being controllable under the EMC Directive, presumably because they are passive and the EMC issues depend solely on what they are connected to or between. Their admission to the Directive might prompt calls for other passive parts to be admitted, notably connectors. There is also a clear problem with assigning responsibility for compliance with a Directive; manufacturers clearly can't supply all cables with every product, as users might well not need all of them and/or might require very long cables. So, should cables, assessed on their own, have to meet requirements based on the most severe operating conditions that can be envisaged?
The Commission has agreed to review its position and will host a workshop soon.
The chief contestants on the industry side seem to be Germany and Netherlands, as the latter has a national scheme for cable assessment, with a quality mark, whereas Germany wants at least a Europe-wide scheme, if not an international one.
A CENELEC report prompted a discussion on LED lamps and lighting, in the context of the PLT standard EN 50561, which is to be updated. There seems to have been a lot of confusion; the potential interference from LEDs into PLT is not (or not primarily) about mains harmonics but about emissions generated by switching circuits.
The report on RTTED states that the new Directive may be published by May 2014, but if not, it will be delayed by European Parliament elections.
IEC published a revised mode for numbering standards in various contexts. It would be helpful for this to be made available generally, but that is unlikely.
Remote participation in Plenary meetings
IEC has now set rules and guidelines for remote participation in formal meetings, for a trial period of one year. However, it does not address the case of participants who are remote even though present in person.
This subject is fraught because the fundamental organization of CISPR (and IEC and most other) committees allows an anomaly to develop. Some topics affect several subcommittees and uniformity should be established by the parent committee. but National Committee members of one or more subcommittees may, within the IEC rules, reject the agreed uniformity measures.
It is now proposed that a draft standard that implements a uniformity proposal shall include a statement to that effect, while one that does not implement it shall also carry an explanatory statement. In this way, National Committees will be alerted to their original voting on the uniformity measure concerned.
Household PLT in the band 30 MHz to 87.5 MHz
prEN 50561-3 has been circulated. Some provisions are still uncertain.
Revised IEC 61000-4-9 (Immunity to impulse magnetic field)
A CD for this revision includes new annexes on the field pattern of the induction coil. measurement uncertainty, mathematical modelling and determination of the 'coil factor'.
CISPR has set up WG2 to the CISPR/S Steering Committee, to promote the use of common terminology between CISPR standards and establish formal definitions.
Battery-operated products with charger port
CISPR officers consider that CISPR standards already cover this case. The product must meet requirements (probably only radiated) when battery operated, but conducted emissions at the mains interface must be considered when the product is being charged. If no charger is supplied with the product, the manufacturer can describe suitable chargers in the instruction book. Presumably if nothing is specified, the product does not conform (and probably does not conform to the applicable safety standard either).
The FDIS (final vote in IEC and CENELEC) was circulated in January. It has failed its vote in IEC, with 26 National Committees (NCs) for and 11 against. But it has passed in CENELEC, although not without significant opposition. European National Committees voting against in IEC were Austria, Belgium, Germany, Italy and Sweden. The USA submitted 72 comments, and Germany submitted 20. UK submitted 29 editorial comments, with a positive vote. Many of the National Committee comments refer to faults that should not occur in an FDIS text.
This is a situation that seems not to have arisen before; often a standard passes in IEC but not in CENELEC. We have not seen the CENELEC voting report, probably because heads are being scratched as to where the standard goes from here. It could emerge as a standard in the EN 50 series, as opposed to the 55 series, but the opposition to that is likely to be strong.
Wireless power transfer (WPT)
CISPR/B has set up a Task force to study the EMC implications of these techniques, in particular, 'air-gap' magnetic induction.
Grid-connected power converters (GCPC) in the context of solar photovoltaic installations
This is a BIG can of worms, and some worms are dissected in this edition's Column. Meanwhile, CISPR/B is looking to include requirements for GCPC above 9 kHz in CISPR 11. Two CDVs have been issued, one for products up to 20 kVA and one above. A third CDV covers 'general maintenance'. The CDVs that pass will be combined in one FDIS for final voting.
CISPR/H is also studying, with CISPR/B, a disturbance and coupling model, which is required to form a rationale for limits and other requirements. A first meeting of the assigned Task Force has taken place, and a second meeting is scheduled for July 2014.
Broadcast and mobile band-sharing in VHF and UHF bands
Mobile radio now uses the UHF spectrum from 790 MHz to 862 MHz, with a gap between 821 MHz and 832 MHz. In 2012, the ITU also allocated 694 MHz to 790 MHz to mobile, on a 'co-primary' basis. The implications of this are still being studied. A questionnaire has been sent to National Committees asking whether CISPR 35 should address this issue (by new requirements for TV antenna port immunity).
Three separate CDVs have been issued for a large amendment to this standard. Those that pass will be combined into one FDIS.
UK experts are fighting a battle over the measurement of conducted emissions into the supply mains. The problem is that present methods assume that differential-mode emissions need not be taken into account, as they produce minimal radiation. This ignores mode-conversion, which can occur at any discontinuity in the mains cables, transferring energy from differential mode to common mode with resulting increased radiation. It ought not to require a big struggle to have this incorrect method of measurement modified, but it is proving very difficult.
The FDIS for a third edition of this standard, on immunity to unidirectional surges, has been circulated. There are signs of annexorrhoea, with four new Annexes added. The UK is not in favour of this document. It includes three different definitions for 'duration', using the same mathematical symbol for each. There seems to be opportunity for improvement.
This is a new standard, on immunity to differential mode mains-borne disturbances (including PLT and others) in the frequency range 2 kHz to 150 kHz. The UK is likely to support the FDIS. A quick appraisal indicates that care has been to eliminate editorial errors, as well a getting the technical matter correct.
The FDIS for a third amendment to this standard has been issued. It will automatically result in a fourth edition of the standard. A further amendment on emissions for LED lamps is being progressed urgently, and is planned to be incorporated in a fully revised 5th edition, conforming to the editorial requirements of the latest IEC Directives Part 2. A first draft of the LED document has been circulated .
IEC SC77B MT12
This committee is responsible for the maintenance of the IEC 61000-4 series standards that deal with immunity to transient phenomena above 9 kHz. It has a large programme of work, and meets twice a year. It is probably not too large a committee to work efficiently.
There are one or seven other, apparently less significant developments for which there is no space this time. More for next time.