Good People, My employer makes both transformers and power supplies, for medical, IT, etc.
After a SFC or abnormal operating condition is concluded, most LVD and MDD safety standards require that the unit passes the respective test level for Reinforced insulation, where there are multiple means of protection required to isolate SELV from hazardous voltage. Also, most of these same standards specifically state that where the test level for Double/Reinforced insulation could be applied across a boundary that is only required to meet the requirements of Basic insulation, that steps be taken to remove the component, or conduct the test so that the Basic spacing or insulation will not be stressed. The most common approach is to perform the di-electric withstand at the test level for Basic insulation on the complete unit (assuming Class 1 construction). The next test is done by providing supplemental insulation where Basic insulation would be stressed, then the test is repeated at the test level for Double/Reinforced insulation. Of course, for Class 2 or 3 construction, then there is no such thing is Basic Insulation... luck, Brian > -----Original Message----- > From: emc-p...@ieee.org [mailto:emc-p...@ieee.org]On Behalf Of Jim > Eichner > Sent: Monday, March 20, 2006 4:35 PM > To: Peter Tarver; emc-p...@ieee.org > Subject: RE: Hipot testing following fault testing > > > The scenario we were really thinking of is in your paragraph starting > with "However..." > > Suppose for example we are fault testing a power supply that supplies > SELV circuits from the mains. There are any number of > faults you could > apply in the p/s control or load circuits that might stress the > transformer. After the test you need to verify that this Reinforced > isolation transformer still has adequate insulation > remaining after the > fault. > > Since it is after a fault, I would argue that the test from > primary to > secondary should be done at the level required for Basic insulation. > Why should it still be Reinforced after a fault has been applied? > > > Jim Eichner, P.Eng. > Compliance Engineering Manager > Xantrex Technology Inc. > phone: (604) 422-2546 > fax: (604) 420-1591 > e-mail: jim.eich...@xantrex.com > web: www.xantrex.com > Confidentiality Notice: This email message, including any > attachments, > is for the sole use of the intended recipient(s) and may contain > confidential and privileged information. Any unauthorized > review, use, > disclosure or distribution is prohibited. If you are not the intended > recipient, please contact the sender by reply e-mail and destroy all > copies of the original message. > > -----Original Message----- > From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Peter > Tarver > Sent: Monday, March 20, 2006 1:56 PM > To: emc-p...@ieee.org > Subject: RE: Hipot testing following fault testing > > Hi, Jim. > > Based on your question, it appears you're discussing faults of > insulation. On that basis, no faulting of Reinforced Insulation is > called for. > > However, if faults: > > on the component containing the Reinforced Insulation (say, > overload testing of a transformer, per Annex C1) [the > concept applied by > extension, even though Annex C was not mentioned in you r question] > > of components other than the component containing the Reinforced > Insulation > > of other insulation > > can cause excessive temperatures or excessive voltages to > appear across > Reinforced Insulation, there is reason to perform a hipot > test after the > fault test on the Reinforced Insulation at the levels called out for > Subclause 5.2. > > Further, in the case of faulting Basic Insulation as a part of Double > Insulation (assuming such testing is accommodated by product > construction), the post fault test hipot would be based on > the value for > and applied across the Supplementary Insulation that was > theoretically > stressed by the fault of Basic Insulation. The idea being that the > second level of protection is not degraded (similar that > pointed out by > your example of earthing remaining intact where it provides > the second > level of protection). > > If you're fault testing components that bridge Reinforced Insulation, > other considerations may come into play, but post fault hipot testing > would likely follow a similar logic to the above. > > Regards, > > Peter L. Tarver, PE > ptar...@ieee.org - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
