Perhaps these days are long past, but there was a time when some switching power supplies were designed as 120/240 supplies without a mechanical switch. They used two energy-storage capacitors in series. At low line voltage, the input rectifier diodes were configured (electronically) as full-wave voltage doubler, charging the two-capacitor combination to the peak-to-peak line voltage. At the high line voltage, the diodes were configured as a bridge to charge the series combination of capacitors to the 0-peak line voltage.
Note that although these supplies would operate from nominal 120 VAC or nominal 240 VAC, there was a range of voltages in between where they would NOT operate! Donald Borowski EMC Compliance Engineer Schweitzer Engineering Labs Pullman, WA, USA From: Kevin Robinson <kevinrobinso...@gmail.com> To: emc-pstc <emc-p...@ieee.org> Date: 01/27/2012 07:23 AM Subject: Is this common knowledge - Electrical Ratings Sent by: emc-p...@ieee.org Happy Friday everyone I am asking a question that I already know the answer to, but I am trying to determine if it is common knowledge or if it was something that I picked up along the way and have always accepted as being true. If you were to see a product with a marked electrical rating of 120/240 V and another product with a marked rating of 120-240V, what would be the difference between these two products? Would a user or operator need to do anything special with one or both of these products to use it at 120V or 240V? Thanks, Kevin Robinson OSHA - ---------------------------------------------------------------- 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 <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. 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 <emcp...@radiusnorth.net> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com> - ---------------------------------------------------------------- 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 <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. 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 <emcp...@radiusnorth.net> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
