At 12:22 +0000 31/1/03, John Woodgate wrote: > >There is a proposed amendment to IEC/EN 60950-1 requiring a test of the >protective conductor network at *prospective short-circuit current* for >the time it takes for the mains circuit protective device to operate. >The details are controversial at present, because the test currents >appear not to have taken into account the differences between >prospective short-circuit currents in different wiring systems and >supply voltages. Given that reservation, the lowest test current is 200 >A. > >The amendment is aimed at protective conductors which are surface or >internal traces of multi-layer printed boards. It is said that such >traces have failed in the field under high-current fault conditions. >--
Is the proposal to replace the existing test in the standard or to add an additional test only for certain special circumstances? Is there any evidence that this test would actually result in a significant number of poorly designed products which currently pass the requirements of the standard being rejected? The existing test has its faults but it is easy to do with some very cheap apparatus. It strikes me that the cost of doing a test at 200+A is potentially very substantial. If the result of an amendment to the standard is that significant numbers of self-certified products which have not been properly tested in this aspect of their design reach the market, then the net result will actually be a significant reduction in the safety of end users. A cynic's view might also be that an amendment of this nature would suit the test labs and larger manufacturers fine, since they will be able to justify the cost of the apparatus required, whereas smaller manufacturers (and yes, small consultancy companies like mine) will not. OK, I admit I'm putting two and two together and getting about seven but I believe one should get one's retaliation in first in these circumstances! Any amendment along the lines suggested should be prepared to sacrifice a fair degree of technical accuracy against the need for the test to be cheap, quick and easy to perform. Nowadays, standards writing should not just about getting accuracy and repeatability in testing but should also take into account the need to ensure that the requirements (and hence the tests) are actually possible to apply in the real world, and not just by people at specialist test houses. Regards Nick. This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
