Could you use a RCD to provide the safety-disconnect function? Much nicer (and safer) than fuses and you can stick whatever you like in the earth conductor. Tony
From: Dean Gerard (Medical Physics) <[email protected]> To: [email protected] Sent: Thu, Oct 15, 2009 11:53 am Subject: [PSES] inductive filter in PEC I'd be grateful for people's views on the wisdom of including an inductive filter (for fast transient suppression) in the protective earth conductor of a device. Since safety in the event of a fault to earth relies. in most installations. upon automatic disconnection of supply, which in turn relies upon low-impedance earth-fault loop, does the inclusion of an inductance in this loop not then compromise this safety feature by potentially increasing disconnection time in the event of such a fault? (the shock hazard being a function of duration as well as magnitude) Furthermore, that part of earth-loop impedance attributable to the device, rather than the installation, is tested by DC earth bond resistance measurement. How valid a measure is this with an inductance present, since the earth-fault will not be DC but at mains frequency and typically generated as a transient step-type function when the fault occurs (to which the inductance will present a much higher impedance). Thanks Ged Dean ________________________________ The information contained in this email may be the subject of public disclosure under the Freedom of Information Act 2000 - unless legally exempt from disclosure, the confidentiality of this email and your reply cannot be guaranteed. Copyright of this email and any attachments created by us remains vested in the Nottingham University Hospitals NHS Trust. This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. This footnote also confirms that this email message has been swept by anti-virus software for the presence of known computer viruses. Nottingham University Hospitals NHS Trust City Hospital campus | Hucknall Road | Nottingham | NG5 1PB | Tel: 0115 969 1169 QMC campus | Derby Road | Nottingham | NG7 2UH | Tel: 0115 924 9924 If you have received this email in error please notify the sender. ID:B4ad6ff1a0000.000000000001.0001.mml - 11:53:14 10/15/09 ________________________________ The information contained in this email may be the subject of public disclosure under the Freedom of Information Act 2000 - unless legally exempt from disclosure, the confidentiality of this email and your reply cannot be guaranteed. Copyright of this email and any attachments created by us remains vested in the Nottingham University Hospitals NHS Trust. This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. This footnote also confirms that this email message has been swept by anti-virus software for the presence of known computer viruses. Nottingham University Hospitals NHS Trust City Hospital campus | Hucknall Road | Nottingham | NG5 1PB | Tel: 0115 969 1169 QMC campus | Derby Road | Nottingham | NG7 2UH | Tel: 0115 924 9924 If you have received this email in error please notify the sender. - 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]> - 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]>
