I have found errors in 6.7.3.2 concerning the sample calculations provided. I'm not aware of an error in Table 9. Circuits derived from Mains would include, in my interpretation, any circuit which derives energy from the mains but which is galvanically isolated from it and often given the term "secondary circuits". Section 6.7.3.1 para b) provides guidance on when to use the awkward clearance calculation in 6.7.3.2 For example, I would classify the working voltage between a mains and a secondary circuit as a mixed voltage or a voltage derived from more that one circuit, thereby requiring the use of 6.7.3.2 to determine clearance. However, I would use Table 5 for determining clearance from a secondary (mains derived) circuit to a grounded, metal enclosure. The determination about whether the clearance is for basic or for reinforced insulation requires information about accessibility and protective bonding. Ralph McDiarmid, AScT Compliance Engineering Group Xantrex Technology Inc.
From: [email protected] mailto:[email protected]] On Behalf Of John Allen Sent: November 30, 2004 5:27 AM To: - EMC PSTC Posts (E-mail) Subject: IEC/EN 61010-1, 2001 'Circuits derived from Mains Circuits' Hi Folks Sub-Clause 6.7.3.1 "Clearance values - General" and Table 5 of Clause 6.7.3. "Circuits other than MAINS CIRCUITS" refers to the term 'Circuits derived from MAINS CIRCUITS'. However, nowhere in the standard are there clear definitions or ranges of examples of what these circuits are, or of what they are not! Neither are there any references to other standards to provide this distinction. Therefore one cannot point clearly to a methodology for deciding what is, or is not, a 'Circuit derived from Mains Circuits' - except possibly that a totally battery powered unit with no charging facilities probably is NOT a 'Circuit derived from Mains Circuits' ! This leads me to the following questions: a) Where, if anywhere, is the dividing line between the two? b) If there is a dividing line, then how many layers of definable compliant insulation, isolation, barriering, transient reduction measures, etc., do you need to need between one and the other? c) If there is not a dividing line, then how the H*ll do you make the distinction and so be able to apply the standard? Thus, if anyone can shed some light on the unspoken meanings of this part of the standard, I would be most grateful! Thanks in advance. John Allen, Technical Consultant EMC and Safety Engineering ERA Technology Ltd. Cleeve Road Leatherhead Surrey KT22 7SA UK Tel: +44-1372-367025 (Direct) +44-1372-367000 (Switchboard) Fax: +44-1372-367102 Please take a minute to visit my recently updated (Sept 04) web pages at http://www.era.co.uk/services/rcm.asp and the main ERA Website at http://www.era.co.uk ********************************************************************** Copyright ERA Technology Ltd. 2004. (www.era.co.uk). All rights reserved. The information supplied in this Commercial Communication should be treated in confidence. No liability whatsoever is accepted for any loss or damage suffered as a result of accessing this message or any attachments. ********************************************************************** _____________________________________________________________________ This e-mail has been scanned for viruses by MCI's Internet Managed Scanning Services - powered by MessageLabs. For further information visit http://www.mci.com ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Ron Pickard: [email protected] Scott Douglas [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 ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Ron Pickard: [email protected] Scott Douglas [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
