Tim, I was referring to one, Kensington 150 Europe version, as per your USA version without earth connection. Could you please give me a link to see the metal case with separate earth connection. You are right that it is difficult to advise the user to have a good connection of the earth if not needed. Does the operating instructions warn the user not to use class 1 products or allow both class 1 and 2 products to be used? I saw some circuit diagrams that primary and secondary are isolated by a isolating transformer and thus earthing the product becomes unnecessary except for the earth pin of power outlet.
Regards, Scott From: Haynes, Tim (SELEX GALILEO, UK) [mailto:[email protected]] Sent: Thursday, March 19, 2009 12:04 AM To: John Woodgate; Scott Xe Cc: [email protected] Subject: RE: Intersting question!! John, all... I personally have five inverters a USA version that is 12Vdc/115Vac with no P.E. and a plastic case and four UK inverters all with metal cases and a separate "earth" connection as well as an earthed neutral via the three pin socket. What is the isolation between the DC and AC circuits? What are the possible failure modes of the equipment connected to the AC output of the inverter? What are the failure modes of the inverter? Are all the failure modes visible to the user or might they be exist without user knowledge? With the above information we might be able to assess the need for the metal inverter case to be "earthed" [or should that be interpreted as "local earth"] to the car chassis. I see the inverter situation as similar to the AC - DC power supply. If the AC-DC isolation is such that the DC can never be connected to the AC (internally) then there is no need for one side of the DC to be connected to earth. If the AC-DC isolation is such that the DC can become connected to the AC live, then the DC would "float" on top of the AC voltage. Touching the "safe" DC and earth would provide an electric shock and so one side (or other) of the DC must be connected to earth - hence the AC fuse will blow if the AC live ever become coupled to the DC. I ask myself, why have all the manufacturers of my UK inverters gone to the trouble and (minor) expense of fitting an external earth stud and giving instructions to connect this stud to the car chassis? It is certainly not aesthetics! I hope that this is a correct assessment - but, as I am in a hurry, I reserve the right to be wrong. :-) Regards Tim SELEX Sensors and Airborne Systems Limited Registered Office: Sigma House, Christopher Martin Road, Basildon, Essex SS14 3EL A company registered in England & Wales. Company no. 02426132 ******************************************************************** This email and any attachments are confidential to the intended recipient and may also be privileged. If you are not the intended recipient please delete it from your system and notify the sender. You should not copy it or use it for any purpose nor disclose or distribute its contents to any other person. ******************************************************************** - 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]>
