An aside related to delayed fuses. Two issues with the subject came up when I was an intern a few decades ago. The fuses were used in ELV circuits so could be touched in application. In use, they got too hot to touch, so said the safety folks. Tasked with finding a lower touch temp fuse to use. Samples from every vendor and some never heard of. Found one, half the resistance, and temp. But unknown source so lots of testing to evaluate performance. Then found that the in-rush current at each turn-on affected the delay mechanics. The fuse used a little solder cup and spring to make connects, and each in-rush caused a slight slip. 5-10 turn on's and it would open. Power supply engineers found a way to limit in-rush current to avoid the condition. Saw this in-rush issue over and over in the following decades.
Bill Owsley EMC First LLC On Wednesday, March 2, 2022, 05:44:09 PM EST, Douglas E Powell <doug...@gmail.com> wrote: Very nice, thanks. Now I may need to convince my client to stop using Slow Blow on international shipments. -Doug Laporte, Colorado USA LinkedIn (UTC -07:00) Mountain Time (US-MST) On Wed, Mar 2, 2022 at 3:34 PM Scott Aldous <00000220f70c299a-dmarc-requ...@listserv.ieee.org> wrote: Hi Doug, As the link Rich provided from Littelfuse indicates, the international symbols come from IEC 60127-1. See the last page of this preview, section 6.1. On Wed, Mar 2, 2022 at 2:22 PM Richard Nute <ri...@ieee.org> wrote: Here is some info: https://www.swe-check.com.au/pages/learn_fuse_markings.php https://www.littelfuse.com/~/media/files/littelfuse/technical-resources/documents/reference-documents/littelfuse_5x20mm-iec-fuse-cap-marking_guide.pdf Rich From: Brian Kunde <bkundew...@gmail.com> Sent: Wednesday, March 2, 2022 1:08 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Fuse designations I do not know where the information I have originally came from, but I got this and have been using this for over 30 years: FF = Very Fast Acting F = Fast Acting (Common) M = Medium Time Lag T = Time Lag (Common) TT = Long Time Lag I got this from Bud Lang who was our Safety Guru at Heath Kit many years ago. The Other Brian On Tue, Mar 1, 2022 at 5:33 PM Douglas E Powell <doug...@gmail.com> wrote: All, Over the years, I've seen various ways people include a caution or warning, in their user documents or product labels, for replacement fuses. Similar to: "replace only with same type and rating of fuse"; followed by a code: T1.6AH250V. And for those who may not understand the code, they may sometimes add in parentheses some variant of "(1.6 Amp time-lag, ~250V, high breaking capacity)". So now to my question, US manufacturers sometimes use the phrase "SLO-BLO" or "Slow Blow" instead of Time-Lag or Time-Delay. Are these terms commonly used internationally and if so, are they clearly understood? I took some time to look up SLO-BLO and found it's a registered trademark for Littelfuse going back to 1957, and it has been continuously renewed since that time. Incidentally, a German Engineer once told me the way he would designate a fuse type for a variety of tripping characteristics was in this order from very slow to very fast: TT1.0A250V, T1.0A250V, 1.0A250V, F1.0A250V, FF1.0A250V. Thanks, -Doug Douglas E Powell Laporte, Colorado USA (UTC -07:00) Mountain Time (US-MST) - ---------------------------------------------------------------- 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://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org> David Heald <dhe...@gmail.com> -- Scott Aldous | Regulatory Compliance Manager | scottald...@google.com | 650-253-1994 - ---------------------------------------------------------------- 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://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org> David Heald <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://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org> David Heald <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://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>