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Before CISPR Frankfurt plus various updates

By J. M. Woodgate B.Sc.(Eng.) C.Eng.  MIET MIEEE FAES

They keep coming!

In spite of the so-called 'holiday season', over 100 new EMC standards committee documents were circulated by BSI since 1 July, and more come every day.

CISPR

The 2014 CISPR meetings will be held in Frankfurt from 13 to 24 October.

CISPR/B

CISPR/B has issued an INF (information document) containing what it hopes to be the FDIS (final voting) text for the sixth edition of CISPR 11. The revised texts were circulated for comment and CDV vote as five 'fractions', and the intention is to pull them all together for the FDIS vote. There is a long explanation of this process in the document. But it has to be said that this is a very difficult process: I've done some of it for other committees and unless you have a photographic memory it's a far from easy task. You have to make sure that a particular clause is not only correct in itself but is also consistent with other clauses in the same document, and often it also has to be consistent with texts in other standards. I've often had to use three computers to display the text being worked on and two or more others. It's especially difficult to check text you have written yourself, as you tend to read what you meant rather than what the words say.

Just as an example, a simple error was found in a table at a very late stage, which caused some administrative fluttering. It's actually pretty obvious that a figure was inadvertently copied from the table row above, but the resulting absence of a step change in the limit at the transition frequency was not unexpected; however the incorrect value was 24.5 dB higher than was intended.

This fully justifies the circulation of the INF document, and the Secretariat advises:

The INF document is submitted for information only and intended to provide an insight in the content of future CISPR 11 Ed. 6.0. The resolution of comments on the CDVs is closed and the only pending action is rectification of the error mentioned above. So please abstain from submission of more comments and opinions other than reports on obvious editorial flaws and bugs still found in the present document.

Comments are required 'before October', but there is concern that National Committees will not consider the document in depth, but wait to (probably) vote down the FDIS. Not constructive!

TC77

New Generic immunity standards have been issued at the CD (Comment) stage; these are second CDs because of the numerous comments received from National Committees on the first CDs. Comments on these new documents are to be sent to BSI by 26 September. The main changes for the residential commercial and light industrial environment are:

  • Improvement of the environmental description (with the aid of very verbose definitions and notes)
  • extension of the frequency range for the radio-frequency electromagnetic field test according to IEC 61000-4-3 (it now covers 80 MHz to 6.0 GHz, with a gap between 1.0 GHz and 1.4 GHz)
  • change of the repetition frequency for the fast transients immunity test according to IEC 61000-4-4 (now 5 kHz or 100 kHz is allowed, with a warning that 5 kHz will be deleted in future. This is contrary to IEC rules: no change can be made without a vote of National Committees at the time. )
  • revision of the test levels (it doesn't say which: the power frequency magnetic field test level is now 10 A/m, the surge test is added for signal and control ports and line-to-earth surges on DC power ports are now 1 kV)
  • consideration of measurement uncertainty (just a cross-reference to IEC TR 61000-1-6 or the relevant Basic standard)
  • addition of Annex A as a guidance for product committees (this is an astonishing throw-back to the very first editions of the Generic standards, which included a list of additional tests that would be required in future. This was highly controversial and the list disappeared from later editions)

What isn't mentioned is that the wording of the definitions of performance criteria A and B have been changed. Notably, the definition of criterion A no longer has the sentence ' The performance level may be replaced by a permissible loss of performance.' There seems no good reason for this change; the sentence is intended to relate the loss to the actual performance level of the sample being tested, not the rated performance level specified by the manufacturer. The new text is actually inconsistent with clause 6, which allows degradation to be specified without restricting it to criterion B.

The main changes for the industrial environment are:

  • Improvement of the environmental description (again, a verbose description; farm buildings are included but do many of them have their own HV or MV/LV transformer? Many of the test levels, too, seem inappropriate for farm buildings)
  • extension of the frequency range for the radio-frequency electromagnetic field test according to IEC 61000-4-3 (increased to 6 GHz, but still with a gap between 1.0 GHz and 1.4 GHz)
  • change of the repetition frequency for the fast transients immunity test according to IEC 61000-4-4  (The same Note, contrary to IEC rules as for the companion standard)
  • revision of the test levels (the surge test is added for signal and control ports and line-to-earth surges on DC power ports are now 1 kV)
  • consideration of measurement uncertainty  (minimal, as for the companion standard)
  • addition of Annex A as a guidance for product committees  (the same as in the companion standard)

The same changes have been made to the performance criteria as for the companion standard. There has to be a question whether all these changes can be shown to be necessary by reports of EMI cases from the field.

The Secretariat claimed to have accepted many National Committee comments but the new drafts do not appear to confirm that. Numerous comments can be expected on them.

While it is true that the range of products to which the Generic standards apply has greatly decreased, it is essential to bear in mind that all product and product-family standards are required to align with the Generics or set more stringent provisions. So changes to the Generics potentially affect everybody.

EMC and functional safety

The progress of IEC 61000-1-2 continues to attract far too many National Committee comments: the British committee alone has submitted ten pages. Surprisingly, the CD has been made into a Draft for Public Comment, which is not usually done until the CDV stage. The closing date for public comments is 31 August, so there may be more British comments to be submitted.

Drafts for Public Comment

BSI issued a batch of DPCs for EMC standards in July, for: 61000-4-39, 61000-4-16 Amendment 3 (which will automatically result in a new edition), 61000-4-13 Amendment 2, CISPR 16/EN 55016 -1-6 Amendment 1, CISPR 11/EN55011 Amendment 1 and CISPR 16/EN 55016-1-4 Amendment 2. BSI has revised the procedure for obtaining DPCs and commenting, details of which can be found on the BSI Standards web site.

CISPR/I

A CDV for CISPR 24 Ed. 2 Amendment 1  has been circulated. This is due to the continued difficulties with CISPR 35.

A new proposal, in the form of a DC, has been made for the control of mains cables leaving a test area. The intention is to include this in CISPR 32. A round-robin test was undertaken to compare the merits of three techniques - VHF-LISN, CMAD and CDNE-M. CMAD suppresses common-mode current, thus indirectly defining the length of the cable, while the other two techniques terminate the lines in specific impedances (but not in the same way). The long and comprehensive report shows the results of the round-robin test and concludes that the VHF-LISN give the best results.