I read in !emc-pstc that Ken Javor <[email protected]> wrote (in <bad43d9e.1f13%[email protected]>) about 'FCC Limits' on Tue, 29 Apr 2003: >At one time I needed to perform MIL-STD-462 power line audio frequency >susceptibility test CS01, which places the secondary of a transformer in >series with power to the test sample. The primary side is driven by an >audio amplifier of low source impedance. In the US, the sole source of the >mil-spec version of this transformer is Solar Electronics. Before I had one >of theirs, I just went out and bought a 2:1 step down ratio transformer >(like the Solar model) that was built just for 60 Hz, and it worked fine in >my application. So that's why I think a 50/60 Hz transformer built for 230 >Volts will attenuate input 150 kHz ripple by twice as much as a transformer >built for 120 Vrms.
Your experience, even at 20 kHz, is not a good guide to what happens at 150 kHz and above. Above the frequency at which the primary winding resonates with its self-capacitance, you no longer have a transformer. If a transformer has an inter-winding Faraday screen (of foil, not a layer of winding), its attenuation of even low radio frequencies is very high. -- 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
