Correct. Surprisingly, we had a client attempt to do that on a product so that it would operate on either 120 U.S. or 230 EU. The heater did work without a problem, but it failed the required power harmonics test miserably. There is also wording in EN61000-3-2 stating that half-wave rectification is NOT allowed except for specific circumstances, none of which applied to his product. Bob R.
--- On Fri, 1/27/12, [email protected] <[email protected]> wrote: From: [email protected] <[email protected]> Subject: Re: [PSES] Is this common knowledge - Electrical Ratings To: [email protected] Cc: [email protected] Date: Friday, January 27, 2012, 1:16 PM I have seen people make this mistake a number of times. A diode does NOT reduce the RMS voltage by a factor of 2. It reduces the POWER by a factor of 2 (full power half of the time). Reducing the RMS voltage by a factor of 2 will reduce the power dissipation in a resistor (i.e., electric heater in a coffee maker) by factor of 4. For a 'dumb' resistive heater, a diode will reduce 240 Vrms to 170 Vrms. Donald Borowski EMC Compliance Engineer Schweitzer Engineering Labs Pullman, WA, USA From: Mick Maytum <[email protected]> To: [email protected] Cc: Dan Roman <[email protected]> Date: 01/27/2012 09:58 AM Subject: Re: [PSES] Is this common knowledge - Electrical Ratings Sent by: [email protected] Dans experience reminded me of a guy who bought a 120 V coffee maker as a present for someone in (old) England. Having some knowledge of AC supplies he bought a 240 V to 120 V travel adaptor so the coffee maker could operate on UK 240 V mains. Unfortunately the adaptor consisted of a series rectifier diode to apply half cycles of the AC. Had the coffee maker been electro-mechanical he might have got away with it. But the maker had sophisticated electronic controls. When powered up for the first and only time the result was spectacular. Mick On 27/01/2012 16:26, Dan Roman wrote: > Marked 120/240V would not necessarily mean a switch needs to be flipped or a selector moved, it could still be auto-ranging. But something marked 120/240V would not be expected to operate at say 150V but something rated 120-240V should. > > I would expect something marked 120/240V to operate in two ranges, at least 108-127 and 216-254 but not necessarily in-between. > > I think most consumers that purchased something locally expect to be able to plug in a device without fiddling with a switch or selector. Probably the most common appliance that has a voltage selector switch paid attention to is a hair dryer during international travel after blowing up the first one! > > Dan > > -----Original Message----- > From: John Cotman [mailto:[email protected]] > Sent: Friday, January 27, 2012 10:35 AM > To: [email protected] > Subject: Re: [PSES] Is this common knowledge - Electrical Ratings > > Presumably: > > Something marked 120-240V should run at any voltage in that range, and you'd > just need to plug it into a suitable supply (one would hope that it is also > rated to cover both 50Hz and 60Hz supplies). > > A 120/240V making is an either one or the other indication, so there might > well be a selector switch. If there is, the manufacturer would be well > advised not to be cryptic unless he likes product returns. > > John C. > > -----Original Message----- > From: Kevin Robinson [mailto:[email protected]] > Sent: 27 January 2012 15:20 > To: [email protected] > Subject: [PSES] Is this common knowledge - Electrical Ratings > > 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 <[email protected]> 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 <[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.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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
