Re: [PSES] safety 60950 and surge suppression circuits
Hi Bill: SPDs, regardless of configuration, are notorious for being prone to failure, either short-circuit or open-circuit or any value of resistance between those two extremes. (One cannot predict the energy the SPD will be required to dissipate.) From a safety point of view, all such failures must be accounted for such that the safety of the equipment is not compromised by any failure of the SPD. If the SPD should fail open-circuit, then expected transients that are therefore not attenuated, must not cause the insulation to fail. Hence, the insulation must pass the hi-pot test without the SPD in place. As for the requirement for the GDT to pass the hi-pot test... ??? I don't have any rationale for this. Best regards, Rich On 5/10/2013 10:11 AM, Bill Owsley wrote: I'm running into a dilemma. Not being a Safety Engineer myself, but rubbing elbows with them... On a piece of ITE equipment, I need some surge suppression for worldwide markets with one annoying requirement for 4 kV, otherwise just 2 kV line to earth, and using either plugable cords or permanent connection, whichever is worse. Now the Safety guys tell me that MOV's alone cannot bridge the insulation (Basic or Functional, I forget.) between primary and earth, when using one of power cable options mentioned above. But a proper qualified (GDT) gas discharge tube can do the bridging. So we figured to use them in series. On a quick and dirty bench test it works to 4 kV. Then the Safety guys pull out the rest of the story and point out 5.2.2 which seems to indicate that the GDT is to meet the Hi-Pot test, 1500 vac. Previously, section, 1.5.9.4 (?) indicates that the surge protection devices can be removed during the Hi-Pot test. But now I have a Surge suppression circuit that has to withstand the same Hi-Pot as the rest of the board. Question is how does a surge protection circuit protect the board when it has to meet the same Hi-Pot test? In other words, when a surge comes along, which is going to break over first? The surge protection or the board? Is the purpose of surge suppression is to keep the clamped voltage below a problem level? What am I missing in this? Thanks... - Bill - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org mailto:emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.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...@radiusnorth.net mailto:emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org mailto:mcantw...@ieee.org For policy questions, send mail to: Jim Bacher j.bac...@ieee.org mailto:j.bac...@ieee.org David Heald dhe...@gmail.com mailto:dhe...@gmail.com - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.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...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
Re: [PSES] safety 60950 and surge suppression circuits
In message 518feba9.7000...@ieee.org, dated Sun, 12 May 2013, Richard Nute ri...@ieee.org writes: As for the requirement for the GDT to pass the hi-pot test... ??? I don't have any rationale for this. If its seal was broken, letting the magic gas out, would it arc over at a lower voltage? -- OOO - Own Opinions Only. See www.jmwa.demon.co.uk They took me to a specialist burns unit - and made me learn 'To a haggis'. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.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...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
Re: [PSES] safety 60950 and surge suppression circuits
On 5/12/2013 12:39 PM, John Woodgate wrote: In message 518feba9.7000...@ieee.org, dated Sun, 12 May 2013, Richard Nute ri...@ieee.org writes: As for the requirement for the GDT to pass the hi-pot test... ??? I don't have any rationale for this. If its seal was broken, letting the magic gas out, would it arc over at a lower voltage? Depends on what's left in the GDT, if anything. - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.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...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
Re: [PSES] safety 60950 and surge suppression circuits
Assuming no tracking from impurities, GDT failure mode is typically open. And personal (anecdotal) experience bears this as correct. But have seen test reports where simulated lightning strikes with enough energy cause failure of body such that CTI adversely affected enough to stay lo-Z. Brian -Original Message- From: emc-p...@ieee.org [mailto:emc-p...@ieee.org]On Behalf Of John Woodgate Sent: Sunday, May 12, 2013 12:40 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: safety 60950 and surge suppression circuits In message 518feba9.7000...@ieee.org, dated Sun, 12 May 2013, Richard Nute ri...@ieee.org writes: As for the requirement for the GDT to pass the hi-pot test... ??? I don't have any rationale for this. If its seal was broken, letting the magic gas out, would it arc over at a lower voltage? -- OOO - Own Opinions Only. See www.jmwa.demon.co.uk They took me to a specialist burns unit - and made me learn 'To a haggis'. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.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...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
Re: [PSES] safety 60950 and surge suppression circuits - GDTs
John, It is true that people used to worry about GDTs venting. In venting the GDT sparkover voltage greatly increased. In fact, there was a US trend to include a Back-Up (air) Gap (BUG) across the GDT component in case this happens. In fact, due to contamination, these BUGs were more unreliable than the GDTs they protected. UL came to the rescue and came up with a standard and expensive testing so that a BUG was unnecessary. Although the term is not much used today, these qualified components were known as Bugless GDTs. I've worked with many major GDT manufacturers and the main life concern these days is voltage degradation with surging. The so-called fast GDTs do degrade in sparkover voltage a lot faster than (well made) standard GDTs. One service provider was replacing SPDs using fast GDTs every two years because of this problem. Surge Protective Devices (SPDs) are complete assemblies made up from terminals, bases, housings and surge protective components (SPCs - GDTs, MOVs, ABDs etc.). I've notice that people wrongly use SPD when they are really talking about a surge protective component, SPC. Regards Mick On 12/05/2013 20:39, John Woodgate wrote: In message 518feba9.7000...@ieee.org, dated Sun, 12 May 2013, Richard Nute ri...@ieee.org writes: As for the requirement for the GDT to pass the hi-pot test... ??? I don't have any rationale for this. If its seal was broken, letting the magic gas out, would it arc over at a lower voltage? - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.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...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
