In message <[email protected]>, dated Thu, 19 Apr 2007, "Tyra, John" <[email protected]> writes:
>We have found that a complaint CEC power supply to be larger in size >and more expensive then a noncompliant one as our power supply vendors >have to use better quality core material and the transformer ends up >being larger. This is for a 'linear' power supply (mains transformer and rectifier). To reduce the no-load power, the induction (flux density) in the core has to go down to 1950 values (like 1 T). That means a bigger core and/or more turns on the windings. V = B*a*w*n V = voltage across a winding (volts), B = induction (flux density) (in tesla), a = core cross-section area (sq. metres), w (omega) = 2*pi* frequency (Hz). The other solution is a switch-mode power supply, which meets the energy-saving requirements but adds to the 'EMC smog' by its conducted and radiated emissions. > >The cost is not insignificant if you have a large volume product which >uses a wall wart.... Well, it depends. With the enclosure and mechanical parts of many products running out at around 10 times the cost of the electronics these days.... -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk There are benefits from being irrational - just ask the square root of 2. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] 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] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________
