But breakfast would take four times longer: P = E²/R If R is fixed, and voltage E is reduced by a factor of 2, then power P goes down by a factor of 4.
A more clever design with two heating elements would put those elements either in series or parallel, depending on the voltage, and operate at the same power in either case. Donald Borowski Senior EMC Compliance Engineer Schweitzer Engineering Labs Pullman, Washington, USA From: "Pete Perkins" <[email protected]> To: "'John Allen'" <[email protected]>, <[email protected]> Date: 05/06/2013 08:52 PM Subject: RE: [PSES] UL warning regarding a wall receptacle Sent by: [email protected] John, I agree with your comment in today's environment but the implementation of the required 'green' technology will require almost every household and commercial electrical product to run from a SMPS. (Well maybe a dumb toaster won't require it, but it could be designed to run on 230V and then take twice as long to make the breakfast toast in those countries using 115V.) Everyone wants smart technology everything so this new scenario should come about rather quickly (maybe in a generation or less). The customer won't care what the system voltage is; perhaps the power company could find clever ways to take advantage of this and relax their system voltage regulation requirement. Or maybe it won't be the power company controlling this but, rather, the smart grid taking power from all the neighbors renewable energy stations and sharing it locally. Should be an interesting time; by then we will have learned more about both protection and operation under these broader V conditions - brownout saver circuits for the low end and better OV protection on the other. It looks like fun times are coming to a power system close to you. :>) br, Pete Peter E Perkins, PE Principal Product Safety Engineer PO Box 23427 Tigard, ORe 97281-3427 503/452-1201 fone/fax [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]>
