Richard, (answering message below) Most safety testing is by inspection of PCB layout, component specs and component ratings. For instance, if you use an approved power supply, the lab usually won't pull any single fault hi-pot tests on your unit. They'll probably be satisfied with performing a hi-pot test on the complete unit. You can rest assured that the manufacturer of your power supply probably suffered through numerous single fault hi-pot tests. As such, they won't be repeated on your design.
However, if there is any doubt, the lab will produce a single fault and test the circuit for a hazardous condition. This is especially true if you design your own power supply, as we have done a few times. Part of this testing may be a hi-pot test. Furthermore, a design may have to pass a hi-pot test after going through the "blocked fan" single faults that you mention; perhaps only to verify that the elevated temperatures didn't compromise any insulation in the unit. This usually isn't the case; since most blocked fan tests don't cause temperature rises sufficient to exceed the temperature ratings of most insulation. After saying all of that; I have to qualify that it's just my opinion based upon my own experience and my now failing memory (I cycle through all three of my girls' names just to get one). Since I'm a safety lab "client", I'll defer the verification of my statements to someone who actually works at a safety lab. Anybody want to help Richard on this one? Chris Maxwell Design Engineer Nettest From: Stone, Richard [mailto:[email protected]] Sent: Tuesday, February 10, 2004 9:40 AM To: Chris Maxwell; Chris Wells; emc-pstc Subject: RE: IEC61010-1 multiple Overvoltage catagories in one circuit??? Chris, for #1 below, are you stating that for a hipot test the NRTL can do a single fault test, remove a part or anything else, being the single fault, then performing a hipot? I dont agree with this logic, please educate me if this is the case. Hipot should be done as a complete unit, intact. with No faults.....willing to learn from this forum.. Temp test is with one fault for heating purposes. hipot? thank you, Richard... Richard A. Stone Excel Switching Corporation Compliance 75 Perseverance Way Hyannis, MA. 02601 508 862 3311 ph. 508 862 3020 fax This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ieee-pses.org/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
