John, I am unsure why there are majority two classes: class 1 with earth protection and class 2 without earth protection, but not only class 2. Class 1 products provide additional protection using the earth path in case of basic insulation at fault. With this inverter and class 1 product, this protection becomes failure. In normal use, there should be no any safety risk. However, in case of basic insulation at fault, it may give less protection to the users.
Regards, Scott From: [email protected] [mailto:[email protected]] On Behalf Of John Woodgate Sent: Tuesday, March 17, 2009 10:38 PM To: [email protected] Subject: Re: Intersting question!! In message <[email protected]>, dated Tue, 17 Mar 2009, Scott Xe <[email protected]> writes: >In the Uk, regardless of class 1 or class 2 products, the product has >to be fitted with a 3-pin plug. How many users do understand the >product required earthing or not? If the answer is NO in general, how >can the users be avoided using below products incorrectly. > > > >For example, the 12 V DC to AC inverter used in car. Normally this >type of product provides a socket accepting a 3-pin plug and has no >earth connection. How can the users be told not to plug in an >appliance that requires earthing? Is there any safety clause to govern >this type of issue? There is no need. There is no 'earth' inside a car. The concept or 'earth'/'ground' is widely misunderstood. In a building, the only reason for 'earthing' stuff is that the electricity supply has the neutral earthed. So if you get an insulation failure between a live part and anything you can touch, and that part is earthed, it's equivalent to a live-to-neutral fault and the fuse or circuit breaker will open. The inverter doesn't have its neutral output connected to the car metalwork (there may be a small capacitor and a high value (megohm) resistor between them). So an insulation failure between live and something you can touch doesn't result in you getting an electric shock, even if you are also in contact with the car's metalwork. Earthing isn't a good way of making products safe, because, as you say, someone might not connect the earth properly, but the product still works. Highly-reliable insulation is MUCH better, because it's fixed in the factory and the user can't interfere with it. But earthing is 'tradition' in most countries, Denmark being an exception. Only their real cows are sacred! -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk Things can always get better. But that's not the only option. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - 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]>
