Hi Jim, This thread takes me 'back to the eighties' (when I first entered the c-a field and was working with UL 478: You are correct with your comments regarding the perceived flammability of line filter caps.
The scenerio is/was that live parts are required to be "enclosed" (in the US, per the NEC and ANSI/UL standards). All can agree to that, I believe. X-caps were (are still?) available both with a flame-rated potting compound and without. Those not meeting requisite flame-ratings for polymeric enclosures were required to be "enclosed" (which could be accomodated by properly flame-rate barriers, potting, or the outer "enclosure" of the device in which they were contained). Also, since standards allow the filter-caps to be wired-in prior to the switch and fuse/s, they are continually "at risk" for equipment that is plugged-in all the time. Regards, Art Michael Int'l Product Safety News A.E. Michael, Editor 166 Congdon St. East P.O. Box 1561 Middletown CT 06457 U.S.A. Phone : (860) 344-1651 Fax : (860) 346-9066 Email : i...@connix.com Website: http://www.safetylink.com ISSN : 1040-7529 ------------------------------------------------------------------ On Wed, 8 Dec 1999, Jim Eichner wrote: > > A couple of other thoughts: > > - Used to be that everyone thought X and Y cap's were hideously > fire-hazardous. Perhaps the UL and CSA standards for line filters > require a can (ie fire enclosure) around them, even if they are approved > and even if the filter goes inside the outer (equipment) enclosure. > > - Potting will allow you to meet reduced creepage and clearance that may > be crucial in obtaining decent high frequency attenuation from the > filter. > > Regards, > > Jim Eichner > > Senior Regulatory Compliance Engineer > Statpower Technologies Corporation > jeich...@statpower.com > http://www.statpower.com > Any opinions expressed are those of my invisible friend, who really > exists. Honest. > > > > -----Original Message----- > > From: POWELL, DOUG [SMTP:doug.pow...@aei.com] > > Sent: Wednesday, December 08, 1999 2:20 PM > > To: emc-p...@majordomo.ieee.org; Treg Listserv (E-mail) > > Subject: RE: Open Frame EMI Filters > > > > > > Hello once again, > > > > I have already received a number of replies to my query indicating > > that the > > metallic enclosure is required for low inductance coupling to the > > components > > or to prevent radiation between circuits within the product. This is > > not my > > question. > > > > Please remember that one of the criteria that I described for the open > > frame > > is the passing all applicable EMC tests. This means that the > > open-frame > > design that I propose meets both radiated and conducted emissions > > levels, > > without the metallic box. My questions deals more with why is the > > enclosure > > required if product passes the tests without it. In the past I have > > designed a few products with a simple PCB for emissions control. I > > compensated for the internal re-radiation problem. > > > > Recently I heard of a commercial EMI Filter company that says the > > enclosure > > is required and that the encapsulant is a requirement. I disagree. > > > > -doug > > > > ======================================= > > Douglas E. Powell > > Regulatory Compliance Engineer > > Advanced Energy Industries, Inc. > > 1625 Sharp Point Dr. > > Fort Collins, Colorado 80525 USA > > m/s: 2018 > > --------------------------------------- > > 970-407-6410 (phone) > > 970-407-5410 (e-fax) > > 800-446-9167 (toll-free) > > mailto:doug.pow...@aei.com > > http://www.advanced-energy.com > > ======================================= > > > > > > > > > > > > > > Hello group, > > > > > > > > For years I have used off-the-shelf and custom EMI filters > > > with a fully > > > > enclosed metal canister. Why is this enclosure required? Are > > there > > > > specific provisions in the standards? My idea is to build > > > up the filter > > > > circuit on a printed circuit board and make it an integral > > > part of the > > > > power supply. > > > > > > > > I am currently looking at EN133200 which has certain seal > > > tests but after > > > > reviewing these, they all appear to be related to climatic or > > > environmental > > > > conditions. If the product passes these tests without the > > > enclosure it > > > > would seem that the product has passed, period. > > > > > > > > Alternatively I have considered removing the nomenclature > > > "EMI filter" and > > > > simply call it an input module, then evaluate it as a part > > > of the overall > > > > system. If it passes the EMC and Product Safety > > > requirements, can I call > > > > the job complete? > > > > > > > > Any thoughts? > > > > > > > > ======================================= > > > > Douglas E. Powell > > > > Regulatory Compliance Engineer > > > > Advanced Energy Industries, Inc. > > > > 1625 Sharp Point Dr. > > > > Fort Collins, Colorado 80525 USA > > > > m/s: 2018 > > > > --------------------------------------- > > > > 970-407-6410 (phone) > > > > 970-407-5410 (e-fax) > > > > 800-446-9167 (toll-free) > > > > mailto:doug.pow...@aei.com <mailto:doug.pow...@aei.com> > > > > http://www.advanced-energy.com <http://www.advanced-energy.com> > > > > ======================================= > > > > > > > > --------- > > > > This message is coming from the emc-pstc discussion list. > > > > To cancel your subscription, send mail to majord...@ieee.org > > > > with the single line: "unsubscribe emc-pstc" (without the > > > > quotes). For help, send mail to ed.pr...@cubic.com, > > > > jim_bac...@monarch.com, ri...@sdd.hp.com, or > > > > roger.volgst...@compaq.com (the list administrators). > > > > > > > > > > > > > > > > > > > > > > > --------- > > > This message is coming from the emc-pstc discussion list. > > > To cancel your subscription, send mail to majord...@ieee.org > > > with the single line: "unsubscribe emc-pstc" (without the > > > quotes). For help, send mail to ed.pr...@cubic.com, > > > jim_bac...@monarch.com, ri...@sdd.hp.com, or > > > roger.volgst...@compaq.com (the list administrators). > > > > > > > > > > --------- > > This message is coming from the emc-pstc discussion list. > > To cancel your subscription, send mail to majord...@ieee.org > > with the single line: "unsubscribe emc-pstc" (without the > > quotes). For help, send mail to ed.pr...@cubic.com, > > jim_bac...@monarch.com, ri...@sdd.hp.com, or > > roger.volgst...@compaq.com (the list administrators). > > > > --------- > This message is coming from the emc-pstc discussion list. > To cancel your subscription, send mail to majord...@ieee.org > with the single line: "unsubscribe emc-pstc" (without the > quotes). For help, send mail to ed.pr...@cubic.com, > jim_bac...@monarch.com, ri...@sdd.hp.com, or > roger.volgst...@compaq.com (the list administrators). > > > --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
