Purple text Gary
From: Fred Townsend [mailto:[email protected]] Sent: Thursday, August 02, 2012 3:09 PM To: 'Derek Walton'; [email protected]; McInturff, Gary; [email protected]; [email protected] Subject: RE: [PSES] EN 61000-4-5 Thanks for the replay Derek. Please see comments inline. From: [email protected] [mailto:[email protected]] On Behalf Of Derek Walton Sent: Wednesday, August 01, 2012 8:15 PM To: [email protected]; [email protected]; [email protected]; [email protected]; [email protected] Subject: Re: [PSES] EN 61000-4-5 Hi Fred, I think you are over reacting here a little, I don't believe anyone is saying a TVS is a current regulator. Derek I wouldn't have posted except for the repeated references to current such as 'of ESD diodes or TVS, they may limit the forward current to 24V'. Neither did I, I was just pointing out that symmetry didn't work for the voltage either - I had no comment on the current. Sorry if that confused the issue Gary The TVS I'm specifically dealing with is essentially a back to back Zener diode with the Die optimized for heat removal between two large electrodes. No disagreement here. You are incorrect saying that these must be used with other additional components. All surges have a defined source impedance, clip Derek you make my point. What defines the source impedance? The network. By network we are not talking about NBC or a LAN. We are talking about the L, C, and R that make up the circuit and connecting networks. Placing TVS directly across a high voltage source is certain death to the TVS as suggested elsewhere in the previous post. TVS are incapable of limiting current and therefore are dependent devices that rely on the network for current limiting. One can not insert them willy-nilly without first addressing the source impedance defining network. which is accounted for in the selection of the part. When you make 8 million a month of a part, you do not include a fraction of a cent more than necessary. If you have a SMPS, then by all means make use of the passive components to aid the TVS. OTOH, if you have a linear regulator, the only filter is for passing the immunity tests. TVS have applications way beyond cleaning up SMPS. There are literally millions of telephone line devices out there with linear power supplies that contain either TVS or gas tubes or both. The En 61000-4-5 spike is widely used, and I am lamenting manufacturers that do not list the current sink capability for this spike of their parts. One GOOD vendor ( others take note ) is ST. Check out Figure 5 here: http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00001367.pdf It would be most helpful if this chart were on all TVS data sheets. I agree they are nice parts with low inductance (also an undefined parameter). One nit-pick, I would not include a Zener as a TVS. Zeners are physically more designed for voltage regulation than the absorption of energy. clip Again we agree. Zeners have much lower peak pulse ratings and are optimized for voltage stability over varying currents. Maybe this is what you were thinking Fred? Not at all Derek. Best regards, Fred Townsend DC to Light Consulting Sincerely, Derek. L F Research -----Original Message----- From: Fred Townsend <[email protected]<mailto:[email protected]>> To: 'Joe Randolph' <[email protected]<mailto:[email protected]>>; 'McInturff, Gary' <[email protected]<mailto:[email protected]>>; jrbarnes <[email protected]<mailto:[email protected]>>; EMC-PSTC <[email protected]<mailto:[email protected]>> Sent: Wed, Aug 1, 2012 9:40 pm Subject: RE: [PSES] EN 61000-4-5 Hi Joe: I have no quibble with your definition of TVS nor extending the term of TVS to surge devices like gas tubes which are both fast and surge capable. My objection is terming to TVS as current regulators or the idea they can be analyzed as standalone devices. The base parameters of the TVS must be summed with the network values, such as inductance, capacitance, and resistance to ascertain their performance levels. Best regards, Fred Townsend From: [email protected]<mailto:[email protected]> [mailto:[email protected]<mailto:[email protected]?>] On Behalf Of Joe Randolph Sent: Wednesday, August 01, 2012 6:11 PM To: Fred Townsend; 'McInturff, Gary'; [email protected]<mailto:[email protected]>; [email protected]<mailto:[email protected]> Subject: RE: [PSES] EN 61000-4-5 Hi Fred: I think that for many people in the industry, the term "TVS" means, simply, "Transient Voltage Suppressor." In this context, "TVS" is just a descriptive term that can be taken to encompass any device that is used to suppress transient voltages. Under this broad definition, devices such as zener diodes, MOVs, sidactors, and even gas tubes could be legitimately characterized as TVS devices. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) [email protected]<mailto:[email protected]> http://www.randolph-telecom.com<http://www.randolph-telecom.com/> Gentlemen: My head is swimming. Forgive me for criticizing but TVS don't limit any current. They are fast transient voltage clamps designed to be members of inductive networks. The clamps are often used to suppress ringing where symmetry is of no concern. See YouTube: http://www.youtube.com/watch?v=5cXUTKg2T1A TVS are optimized for speed and therefore not very good surge suppressors. Their voltage rating is usually pegged just above the circuit sustaining voltage. Capacitive networks generally don't need transient suppression. MOVs are surge suppressors usually rated in KVA or joules of energy. See YouTube http://www.youtube.com/watch?v=gQ5hHBVWOB4 MOV handle much more energy at the expense of speed. Where transient and surge protection are needed (say lightning), then both TVS and MOVs are jointly used. Both TVS and MOVs are designed to be members of networks and don't work very well as standalone devices. OK I'll crawl back into my hole now. Fred Townsend DC to Light Insulting -----Original Message----- From: [email protected]<mailto:[email protected]> [mailto:[email protected]] On Behalf Of McInturff, Gary Sent: Wednesday, August 01, 2012 4:21 PM To: '[email protected]<mailto:[email protected]>'; '[email protected]<mailto:[email protected]>' Subject: RE: [PSES] EN 61000-4-5 Non symmetry is also the case of ESD diodes or TVS, they may limit the forward current to 24V, but the reverse might be 18 Vdc, and that varies from vendor to vendor even though they are rated on the data sheet similarly Gary -----Original Message----- From: John Barnes [mailto:[email protected]] Sent: Wednesday, August 01, 2012 3:55 PM To: [email protected]<mailto:[email protected]> Subject: Re: [PSES] EN 61000-4-5 Derek, I ran into a similar problem about six years ago, where a 10-30VDC product for use on earth-moving equipment had its DC power protected by a Microsemi 1.5KE51CA-T bidirectional transient suppressor. Applying a single -1kV EN 61000-4-5 surge between power and ground would short out the transient suppressor with fancy fireworks and lots of smoke. In the first page of the datasheet for the 1.5KE51CA-T http://www.microsemi.com/en/sites/default/files/SA4-15.pdf under Applications/Benefits is the comment: "Secondary lightning protection per IEC61000-4-5 with 2 Ohms source impedance: * Class 2: 1.5KE5.0A to 1.5KE24A or CA * Class 3: 1.5KE5.0 to 1.5KE12A or CA" Our fix was to solder a second 1.5KE51CA-T in anti-parallel with the first one, which got us through the immunity requirements of EN 61326:1997 with no more problems. Apparently these transient protectors are bidirectional but not symmetrical-- their breakdown voltages and surge capabilities are different in the forward and backward directions. John Barnes KS4GL, PE, NCE, NCT, ESDC Eng, ESDC Tech, PSE, Master EMC Design Eng, SM IEEE dBi Corporation http://www.dbicorporation.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 <[email protected]<mailto:[email protected]>> 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 <[email protected]<mailto:[email protected]>> Mike Cantwell <[email protected]<mailto:[email protected]>> For policy questions, send mail to: Jim Bacher: <[email protected]<mailto:[email protected]>> David Heald: <[email protected]<mailto:[email protected]>> - ---------------------------------------------------------------- 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 <[email protected]<mailto:[email protected]>> 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 <[email protected]<mailto:[email protected]>> Mike Cantwell <[email protected]<mailto:[email protected]>> For policy questions, send mail to: Jim Bacher: <[email protected]<mailto:[email protected]>> David Heald: <[email protected]<mailto:[email protected]>> - ---------------------------------------------------------------- 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 <[email protected]<mailto:[email protected]>> 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 <[email protected]<mailto:[email protected]>> Mike Cantwell <[email protected]<mailto:[email protected]>> For policy questions, send mail to: Jim Bacher: <[email protected]<mailto:[email protected]>> David Heald: <[email protected]<mailto:[email protected]>> Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) [email protected]<mailto:[email protected]> http://www.randolph-telecom.com<http://www.randolph-telecom.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 <[email protected]<mailto:[email protected]>> 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 <[email protected]<mailto:[email protected]>> Mike Cantwell <[email protected]<mailto:[email protected]>> For policy questions, send mail to: Jim Bacher <[email protected]<mailto:[email protected]>> David Heald <[email protected]<mailto:[email protected]>> - ---------------------------------------------------------------- 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 <[email protected]<mailto:[email protected]>> 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 <[email protected]<mailto:[email protected]>> Mike Cantwell <[email protected]<mailto:[email protected]>> For policy questions, send mail to: Jim Bacher <[email protected]<mailto:[email protected]>> David Heald <[email protected]<mailto:[email protected]>> - ---------------------------------------------------------------- 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 <[email protected]<mailto:[email protected]>> 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 <[email protected]<mailto:[email protected]>> Mike Cantwell <[email protected]<mailto:[email protected]>> For policy questions, send mail to: Jim Bacher <[email protected]<mailto:[email protected]>> David Heald <[email protected]<mailto:[email protected]>> - ---------------------------------------------------------------- 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 <[email protected]> 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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
