In message <00b001c75cc1$233a3810$154d4d0a@MmPc21>, dated Fri, 2 Mar 2007, Piotr Galka <[email protected]> writes:
>My question is: What the voltage will be when the frequency is such >that ferrite is only resistive and 0 inductive ? Is it still trafo or >the wires are just two separate resistors ? It's a very good question, but it's a bit wrongly-stated, I think. There is a long technical piece in the Fair-Rite catalogue 13th edition (1998), which is very helpful on the subject, but I don't know if it is in later editions. What happens as you increase the frequency is that initially the inductance of the bead stays roughly constant, but the loss resistance increases roughly with the square of frequency. At higher frequencies, the loss resistance continues to rise, while the inductance decreases; there is a frequency range where it is inversely proportional to frequency and than at higher frequencies still it decreases very steeply. Up to the frequency where the inductance begins to decrease, and a bit beyond, there is significant transformer action, but, depending on the circuit impedances, it becomes less effective as the frequency increases. However, the inductive effect doesn't disappear entirely until a much higher frequency. What this means, as with so many things about EMC, is that what happens in your particular case can be calculated with difficulty but measured with relative ease. -- 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 ______________________________________________________________________
