Hi Piotr, The interrupt rating for fuses is generally much higher than a PTC max current rating. 5000A is not uncommon, whereas a PTC will have something more like 40A.
IEC 61010-1 allows Basic Insulation between circuits with a potential difference to be considered acceptable as protection for fire hazards, but IEC 60950-1 does not have this kind of provision. Maybe this is obvious, but if you don't want to depend on any external factors, you could just use a fire enclosure. You could also add barriers or a sort of mini fire enclosure around the fuse. Scott Aldous Compliance Engineer Advanced Energy Tel: 970-407-6872 Fax: 970-407-5872 From: Piotr Galka [mailto:[email protected]] Sent: Friday, September 18, 2009 9:42 AM To: EMC-PSTC; Aldous, Scott Subject: Re: Looking for Source of Requirement Hi Aldous, ----- Original Message ----- From: "Aldous, Scott" <[email protected]> > PTCs have a max. current limit standard fuses also > Why don't you use fault testing to determine acceptability of that portion > of the circuit that is not LPS? Method 2 of clause 4.7.1 allows this. I supposed it should be possible to design 12V/0.3A device needing no testing. > Clause 4.7.2 does not require a fire enclosure for nonLPS circuits where > fault testing shows that temperatures sufficient for ignition are not > present (see also 4.7.2.2). Pick the worst case/highest output current > power supply your product could be connected to for your test. Once again, > this requires an instruction in the manual that the supply used cannot be > cable of providing more current than the supply used for the test. If I write that power supply can be 12V and up to 5A isn't it the same as asking for LPS power supply ? As a designer I'd like to be 100% sure of my design before testing and I'm looking for instructions in 60950-1. I don't know how high the temperature can rise if there is shortage in the socket destined for powering the device (with 5A thin cables can be the source of hi hitting). I understand (may be wrongly) that socket (terminal block) is the element and like other elements I should consider it being shorted. In my (certainly not expert) opinion if the distance between terminal blocks for + and for - is enough big (don't know how big) and + is directly connected to 1A fuse (having the right certifications), and whole fuse is in enough distance from - than device should be 100% fire save, but I didn't found that in 60950-1. Best Regards Piotr Galka This message, including any attachments, may contain information that is confidential and proprietary information of Advanced Energy Industries, Inc. The dissemination, distribution, use or copying of this message or any of its attachments is strictly prohibited without the express written consent of Advanced Energy Industries, Inc. - 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.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. 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]>
