Class III equipment shall be designed to be supplied at voltages up to 120V, and that it must be connected to a SELV or PELV circuit.
ELV levels depend on the environmental conditions of the skin – immersed, wet or dry, with DC limits in IEC61201 of 0V, 35V and 70 V respectively. This DC limit may be higher for charging batteries. I don’t have a copy of UL 1703, but assuming Photovoltaic cells are designed to be installed outdoors (!), a maximum contact voltage of 30V dc, is the same as that for outdoor IT equipment in 60950-22, and not far off the 61201 ELV limit for “Wet” skin or 35V Regards Charlie From: Lauren Crane [mailto:[email protected]] Sent: 30 July 2009 15:18 To: [email protected] Subject: [PSES] "safe" voltage differences between UL 1703 and IEC 61140 A colleague has stumped me with the following question. ================== A supplier of a Photovoltaic panel cited IEC 61140 (Protection against electric shock – Common aspects for installation and equipment) as referencing a "safe" voltage to be as high as 120 Vdc. This is puzzling because UL 1703 (Flat-Plate Photovoltaic Modules and Panels) appears to define the electric shock threshold at 30 Vdc. How can electric shock threshold for UL 1703 be set at 30 Vdc, but IEC 61140 considers the upper "safe" limit to be 120 Vd.c.? *************************************************************************************************************** IEC 61140 - Protection against electrical shock - common aspects for installation and equipment Section 7.4 Class III Equipment Equipment relying on limitation of voltage to ELV values as provision for basic protection and with no provision for fault protection. 7.4.1 Voltages 7.4.1.1 Equipment shall be designed for a maximum nominal voltage not exceeding 50V a.c. or 120 V d.c. ripple free. ... NOTE 2: According to clause 411 of IEC 60264-4-41, class III equipment is accepted only for connection to SELV and PELV systems. ***************************************************************************************************************** Any ideas on the rational behind this difference? Regards, Lauren Crane Product Regulatory Analyst Corporate Product EHS Lead Applied Materials Inc. Austin, TX 512 272-6540 [#922 26540] - external use - Save paper and trees! Please consider the environment before printing this e-mail. - 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]>
