I suspect many of the standards committee have merely adopted the Vpeak limit from other standards without giving it much thought. Note that 42.4Vpk is just root2 x 30Vrms. That seems to be all there is to it and I doubt it's mere coincidence. (60Vdc/30Vrms/42.4Vpk found in several standards)
I went back to first principles, did the integration of a d.c pulsed waveform and then again for an a.c. waveform with same amplitude, same duty ratio. I found a much higher effective value (RMS) with the a.c. waveform having sample amplitude and pulse duty ratio. For example, Root2 higher for 50% duty cycle and Root10 higher for 10% duty cycle. Now, the NRTL won't be interested in any of that, but you need to weigh the intent of the standard versus any other risk analysis might do above and beyond the "letter of the law" before deciding on whether those terminals are in fact shock hazardous. It's your product, your call, your corporate reputation, so whatever the decision, it needs to be justified with due diligence. I would say your power supply output as described satisfies the criteria of "limit values for accessible parts" as defined in IEC61010 3rd edition. (33 Vrms, 33xroot2 Vpeak, and 70 Vdc ) A project holder at an NRTL might disagree. Ralph From: Richard Nute <ri...@ieee.org> Sent: Monday, February 26, 2024 12:08 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] 61010-1 hazardous live classification Hi James: In the pulse mode, 46 volts peak exceeds the 42.4 volts peak limit. In accordance with the 61010 standard, the voltage cannot be accessible in the pulse mode. However, the pulse mode is dc (the current does not reverse). The RMS of such a pulse is 46 times the square root of the duty cycle. The shorter the duty cycle, the less human sensation of the pulse. Chances are that the pulse is not detectable by a human finger any more than 60 volts DC. But the standard does not allow such a determination. You are stuck. Best regards, Richard Nute Bend, Oregon, USA From: James Pawson (U3C) <ja...@unit3compliance.co.uk <mailto:ja...@unit3compliance.co.uk> > Sent: Monday, February 26, 2024 5:38 AM To: EMC-PSTC@LISTSERV.IEEE.ORG <mailto:EMC-PSTC@LISTSERV.IEEE.ORG> Subject: [PSES] 61010-1 hazardous live classification Hello all, I hope this safety question is a fairly simple one for you, it being Monday after all. 1. A piece of equipment with a power supply output for driving a lamp. It has two modes, DC and pulsed. 2. Both of the output voltage connections are on accessible terminals (checked using finger probe) 3. Classifying voltages as per EN 61010-1 clause 6.3.1 (limit values for accessible parts, normal operating conditions) 4. DC mode runs at 46Vdc maximum. This is less than 60Vdc so is not Hazardous Live 5. Pulse mode runs at 46Vdc pulsed (frequency up to 1kHz, duty cycle can vary down to 0.01%) which is an AC waveform greater than 42.4V peak so is Hazardous Live 6. The output from the equipment is low impedance so is more than capable of sourcing the required 0.7mA through the IEC 60990 body model. Quick sketch attached to illustrate the concept. I even ran a SPICE simulation to make sure I wasn't getting something wrong. I would appreciate the sanity check! All the best James _____ 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-PSTC@LISTSERV.IEEE.ORG <mailto:EMC-PSTC@LISTSERV.IEEE.ORG> All emc-pstc postings are archived and searchable on the web at: https://www.mail-archive.com/emc-pstc@listserv.ieee.org/ <https://www.mail-archive.com/emc-pstc@listserv.ieee.org/%20> Website: https://ewh.ieee.org/soc/pses/ <https://ewh.ieee.org/soc/pses/> Instructions: https://ewh.ieee.org/soc/pses/list.html (including how to unsubscribe) <https://ewh.ieee.org/soc/pses/list.html> List rules: https://ewh.ieee.org/soc/pses/listrules.html For help, send mail to the list administrators: Mike Sherman at: msherma...@comcast.net <mailto:msherma...@comcast.net> Rick Linford at: linf...@ieee.org <mailto:linf...@ieee.org> For policy questions, send mail to: Jim Bacher at: j.bac...@ieee.org <mailto:j.bac...@ieee.org> _____ To unsubscribe from the EMC-PSTC list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC <https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1> &A=1 - ---------------------------------------------------------------- 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-PSTC@LISTSERV.IEEE.ORG All emc-pstc postings are archived and searchable on the web at: https://www.mail-archive.com/emc-pstc@listserv.ieee.org/ Website: https://ewh.ieee.org/soc/pses/ Instructions: https://ewh.ieee.org/soc/pses/list.html (including how to unsubscribe) List rules: https://ewh.ieee.org/soc/pses/listrules.html For help, send mail to the list administrators: Mike Sherman at: msherma...@comcast.net Rick Linford at: linf...@ieee.org For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> _________________________________________________ To unsubscribe from the EMC-PSTC list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1
