Cannot believe that fellow power suppliers did not jump on this. My employer has a active and popular model series of component power supplies rated 120/240V. Only time that we dived into the lower-end market. Very simple and reliable thyristor-controlled auto-switch, with very small dead-zone. This type of design is found in lo-end 'passive' PFC stuff. Several competitors has similar offerings, and there is a China company that has directly copied my employer's design. So this auto-switch stuff is still common.
from 60950-1 "Equipment shall be designed to be safe at any supply voltage to which it is intended to be connected." -> Does not say it has to work, just not make a mess. Furthermore, 60950-1 also says "- Multiple RATED VOLTAGE: 120/230/240 V. This means that the equipment is designed to be connected to an AC MAINS SUPPLY having a voltage of 120 V or 230 V or 240 V, usually after internal adjustment." And clause 1.4.5 indicates that an input rating of x/y can be used to infer the dead zone. Note to government technical employees - there is no such thing as "common knowledge". 'Common' knowledge is the realm of generalizations and bureaucracy. 'Common' knowledge is ill-suited for use by engineers where standards and empirical data should drive the discipline. Brian -----Original Message----- From: [email protected] [mailto:[email protected]]On Behalf Of [email protected] Sent: Friday, January 27, 2012 8:13 AM To: Kevin Robinson Cc: emc-pstc Subject: Re: Is this common knowledge - Electrical Ratings 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 <[email protected]> To: emc-pstc <[email protected]> Date: 01/27/2012 07:23 AM Subject: Is this common knowledge - Electrical Ratings Sent by: [email protected] 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]>
