I agree that the issue still exists. As I indicated, there is less of a need to address leakage current. I didn't indicate that there was no issue.
The world of machinery is full of large induction motors requiring power factor correction, and variable frequency drives requiring line filtering. There are requirements of industry that result in capacitors from line to ground, and therefore significant current shunted into the ground connection. The potential leakage currents are high and the consequences of contact with an improperly grounded system are severe. However, industry in general has a rather good track record of preventing this type of injury. I will grant that there are plenty of instances of faulty installations, and there are injuries and fatalities. But there is a difference between the industrial installations and residential installation. In industrial installations, grounded system are the rule and faulty grounds represent a fault that has occurred through improper installation or maintenance. At least in the United States, there are plenty of residential installation that were wired as two-wire ungrounded systems. The use of a high leakage current product on one of these systems can have disastrous consequences, and the LVD which covers products for this environment must address leakage current. The Machinery Directive addresses the risk of leakage current through installation requirements including instructional safeguards. It assumes that machinery will be installed by trained or instructed personnel. The LVD assumes laymen will be connecting the equipment and as such has the limits and testing requirements for leakage current. Even then, there are exceptions. IEC 60950-1 does not have specific leakage current limits for products that are permanently connected or that have an industrial locking plug. The connection type is such that the product will either be installed by trained personnel or connected to an outlet that, if installed properly, has a ground connection. For those interested in seeing how things can go wrong in commercial and industrial installation, I recommend Electrical Construction and Maintenance magazine's Illustrated Catastrophes column. http://ecmweb.com/nec/illustrated_catastrophes/ The magazine also has a forensic column where you can find specific cases of electrocutions, including details on the faults leading up to accidents. There isn't a specific menu option or link at the web site, but you can find the articles by typing "case of the" into the search box. Ted Eckert Compliance Engineer Microsoft Corporation [email protected] The opinions expressed are my own and do not necessarily reflect those of my employer. All information in this e-mail is open to debate and should not be used as guidance in matters of prodcuct testing or certification. Your mileage may vary. Results are not necessarily typical. Limit one coupon per customer. -----Original Message----- From: John Woodgate [mailto:[email protected]] Sent: Monday, September 26, 2011 12:06 PM To: [email protected] Subject: Re: EN 60204 In message <e9c52f9e77c43c49a56a22691b3680be117...@tk5ex14mbxc301.redmond.corp.micro soft.com>, dated Mon, 26 Sep 2011, Ted Eckert <[email protected]> writes: >As such, there may not be as much of a need to address leakage current >under the Machinery Directive. I can understand your reasoning, but since excessive leakage is one of those faults that can persist undetected until someone gets a severe electric shock, I think it does need to be addressed. There is also an in-situ EMC issue: leakage current creates magnetic fields that are not often counteracted by those of an adjacent conductor carrying the same current in the opposite direction. I had experience of this in a graphics workshop where current in the armour of an under-floor cable caused CRT displays to jitter vertically by about 1 mm, causing sever eye-strain. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK When I point to a star, please look at the star, not my finger. The star will be more interesting. - ---------------------------------------------------------------- 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://product-compliance.oc.ieee.org/ 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://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. 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