Martin Having read several other contributors comments on your question, I have to say that I totally agree with them (test with the switch in both positions) for one very practical reason.
I know of several occasions where personnel have lifted disconnected equipment by wrapping their arms around it - and then dropped it again by reflex when their fingers touched the pins of the plug and they got a non-fatal shock from the charged capacitors on the plug-side of the switch. In one case the person suffered a badly injured foot (20-30lbs from 4feet up make a hell of an impact on your foot), and in the other case the weight missed the person's foot - but I then spent many hours trying to defend my company which supplied the equipment (even though it complied with the standard IEC380 - it was a long time ago! - and met the same requirements as 60950 does now)! I would expect that other forum participants will be able to relate similar incidences. Personaly, based on the above experiences, I play safe and apply the test whatever capacitance is across the pins with the switch open. As I said for the second example, even capacitance at/below the compliance limit is enough to cause the reflex action which may cause the recipient of the shock to involuntaritarily do something which results in harm to himself (or someone else). Given the current effects of product liability legislation I would take any chances at all! John Allen Thales Defence Communications Division Bracknell, UK -----Original Message----- From: marti...@appliedbiosystems.com [mailto:marti...@appliedbiosystems.com] Sent: 11 May 2001 17:31 To: emc-p...@majordomo.ieee.org Subject: Capacitor Discharge Test We evaluate our laboratory equipment to UL 3101-1, CSA 1010.1 and EN 61010-1. Section 6.10.3 of UL 3101-1 states "If plug pins of cord-connected equipment receive a charge from an internal capacitor, the pins shall not be HAZARDOUS LIVE 5s after disconnection of the supply". We have always performed this test with the power switch in the ON position and would have the unit running then unplug the power cord and take our reading on the oscilloscope. We have never measured any voltages above the HAZARDOUS LIVE limits of 30Vrms, 42.4V peak or 60Vdc. Our new NRTL Engineer has now also requested us to perform this test with the power switch in the OFF position. With the switch in the off position our voltages after 5 seconds are close to line voltage. The NRTL is considering this a failure. However, UL 3101-1 also states in Section 6.10.3 "For plugs receiving a charge from an internal capacitor, the measurements of 6.3 are made to establish that the levels of 6.3.1.3 are not exceeded." 6.3.1.3 requires measuring the overall capacitance from the unit. Our NRTL states that there is no method available to measure the overall capacitance of the unit. Has anyone else in the group had any experience with this issue? Does your NRTL require testing with the switch in the OFF position? Do your units fail with the switch in the OFF position? Is it a failure just because the voltage limits are exceeded, or is it only a failure if the current and capacitance limits are exceeded. (Similar to the Permissible Limits Requirements). Have you had any experience with NRTL's not being able to measure the overall capacitance? All responses are greatly appreciated. Regards Joe Martin Applied Biosystems marti...@appliedbiosystems.com ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: pstc_ad...@garretson.org Dave Heald davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.rcic.com/ click on "Virtual Conference Hall," ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: pstc_ad...@garretson.org Dave Heald davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.rcic.com/ click on "Virtual Conference Hall,"
