Also, one other thing to keep in mind is that 150VDC is only the working voltage for determining the creepage distance...to determine the proper clearance and Dielectric withstand test, one must take the peak ringing voltage into consideration. The applicable clearance here, would be 1.4mm (assuming a maximum ringing voltage of 280Vpeak...this, I believe, would be a very safe guess).
- Mel ---------- From: Mel Pedersen[SMTP:mpeder...@midcom.anza.com] Sent: Monday, October 12, 1998 8:42 AM To: emc-p...@majordomo.ieee.org; 'Diaco Davari'; 'Barry Esmore' Subject: RE: Crepage/Clearance On Telecom Modem design This is my understanding of the situation Barry. If one considers the worst case (DC) voltages that could possibly exist on TNV-3 lines and also SELV circuits, and considers the likelihood that these are at opposite polarity, one would obtain a worst case 180VDC = -120VDC (TNV-3) - 60VDC (SELV). Everyone knows, however, that 120VDC is not likely on a subscriber loop that is TNV-3, it is more likely 48VDC nominal. Also, everyone knows that, on the SELV side, chips are not powered at 60VDC. Therefor, 150VDC is generally accepted as the BASIC INSULATION working voltage at the TNV-3/SELV interface. I have spoken with a few people in the industry about this, as well as some European test labs/Notified Bodies for the LVD and TTE directives. I have also seen this value (150VDC) pop up a few times for the working voltage at this barrier. Any input from a European test lab? Hope this helps Barry. Mel Pedersen Midcom, Inc. Homologations Engineer Phone: (605) 882-8535 mpeder...@midcom-inc.com Fax: (605) 882-8633 ---------- From: Barry Esmore[SMTP:bar...@melbpc.org.au] Sent: Friday, October 09, 1998 11:47 PM To: Mel Pedersen; emc-p...@majordomo.ieee.org; 'Diaco Davari' Subject: Re: Crepage/Clearance On Telecom Modem design Mel, I notice you mentioned that European labs are using a working voltage of 150 Vdc which requires 1.6 mm creepage. I have assumed they were using 125 Vdc which requires only 1.5 mm. Probably the safest course is to go for the higher 1.6 mm unless the product is destined for a country requiring 230 volt Supplementary Insulation. Can anyone confirm what working voltage labs are using for Basic Insulation of TNV circuits? Regards Barry Esmore ---------- > From: Mel Pedersen <mpeder...@midcom.anza.com> > To: emc-p...@majordomo.ieee.org; 'Diaco Davari' <dav...@pmc.philips.com> > Subject: RE: Crepage/Clearance On Telecom Modem design > Date: Friday, 9 October 1998 11:51 > > I believe that your experts are wrong...4.2 is a rather odd number to come up with. The most common requirement here is SUPPLEMENTARY INSULATION for a PRIMARY CIRCUIT at 250Vrms (as defined by EN 60950) between the TIP/RING (line side, or TNV-3 side) and the modem or device side. 2.5mm of surface creepage and 2.0mm of air clearance is required here. This assumes that your modem or device side already has sufficient isolation from Mains, which is almost always the case. > > Many countries in Europe require only BASIC INSULATION at a working voltage of 150VDC, which equates to a 1.6mm creepage spacing requirement. This also assumes that you have sufficient isolation from Mains to you modem. > > If you don't have sufficient isolation from Mains, your requirement will be 5.0mm. This would be consistent with the REINFORCED INSULATION requirement between Mains and the Tip/Ring side. > > It is possible that your consultants are correct for your particular case...however, it would be a very unusual case... > > They are correct about one thing...EN 60950 is the correct standard. > > feel free to call if you have any further questions, > > Mel Pedersen Midcom, Inc. > Homologations Engineer Phone: (605) 882-8535 > mpeder...@midcom-inc.com Fax: (605) 882-8633 > > I disclaim anything that may be wrong. > --------- 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, j...@gwmail.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, j...@gwmail.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, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
