I read in !emc-pstc that Neil Helsby <[email protected]> wrote (in <[email protected]>) about 'Harmonics and conducted emissions' on Tue, 27 May 2003:
>Has anyone else noticed the tendency of modern switch mode power supply >designers to save manufacturing costs at the expense of harmonic and >conducted emissions measurements? Did you mean to write 'measurements' in that sentence? It doesn't make sense, really. > >EN 61000-3-2:2000 has introduced the concept of Partial Odd Harmonics for the >21st and above. While this adds extra functions to the spread-sheet >results check, I wonder if it also has an unhelpful side effect. I don't see that this is necessarily relevant to the next paragraph, about conducted emissions, which are still mostly measured from 150 kHz upwards. The 'partial odd harmonics' thing deals with harmonics up to the 39th only. That's 1950 Hz in Europe and 2340 Hz in the Americas. Are you measuring conducted emissions down to 9 kHz? > >With conducted emissions, new power supply designs generate peak >emissions at frequencies below 200 KHz that increase in level inversely >to the frequency. I don't see anything 'new' in that. It applies to all SMPS, with suitable changes to the '200 kHz'. >These out-of-band emissions result in overloading the >front-end of a Spectrum Analyser that consequently requires either a >pre-selector or calibrated filter to function correctly. There is, of >course, the alternative of purchasing a new receiver! This overloading has been around for a very long time. It is one of the disadvantages of using a spectrum analyser instead of a CISPR receiver. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL! This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
