In message <ofa70d512d.43c9491c-on882571ff.00528f80-882571ff.00533...@selinc.com>, dated Fri, 6 Oct 2006, [email protected] writes
>Since we are on the subject, let me toss in my two cents, even though I >don't believe this to be the problem in this case. > >I have seen the characteristics of ferrite cores changed (apparently >permanently) I think it can be changed back. >by passing a high current pulse though the inductor winding. This may >seem like an unlikely situation until one thinks about a ferrite >inductor on a power supply rail, and the rail then accidentally shorted >to ground. > >The current pulse reduces the inductance substantially. If the core is a closed magnetic circuit, it remains magnetized after the pulse is over. This substantially reduces the incremental permeability. It can probably be 'degaussed' in the usual way by applying a damped or manually reduced sinusoidal current, initially equal to the peak pulse current. Maybe someone could try this and report back. Some ferrite cores, and possibly all iron dust cores, have non-magnetic constituents that act as distributed air-gaps and these cannot be 'permanently' magnetized. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk Swine wave - a waveform whose spectrum is exceptionally difficult to calculate. 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 ______________________________________________________________________
