Building a transformer
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From: J. B. Wood on 15 Aug 2006 07:11 In article <-M2dnYH0Js-9cH3ZnZ2dnUVZ_r6dnZ2d(a)adelphia.com>, John Popelish <jpopelish(a)rica.net> wrote: > In addition to the filter and secondary current comments: > If you don't load the two outputs equally, there will be Dc in the > transformer core, causing it to saturate at the end of alternating > half cycles. It will hum and get hot. Hello, and direct current in the core as a result of current flow in the secondary windings? Just how would that be possible? Is the core part of some external circuit? If you mean eddy currents they would be AC and a power transformer core is laminated to minimize this effect. Either I misconstrued your comment or I must have been sleeping in my EE101 electric machinery course years ago. Sincerely, John Wood (Code 5550) e-mail: wood(a)itd.nrl.navy.mil Naval Research Laboratory 4555 Overlook Avenue, SW Washington, DC 20375-5337
From: Phil Allison on 15 Aug 2006 07:26 "J. B. Wood" > John Popelish > >> In addition to the filter and secondary current comments: >> If you don't load the two outputs equally, there will be Dc in the >> transformer core, causing it to saturate at the end of alternating >> half cycles. It will hum and get hot. > > > Hello, and direct current in the core as a result of current flow in the > secondary windings? ** Of course not. Always exclude the impossible when interpreting someone's language. In this case "DC" is an abbreviation of "DC offset " = magnetic field offset. > If you mean eddy currents they would be AC and a > power transformer core is laminated to minimize this effect. ** WRONG. The heat is generated by simple I squared R loss in the copper wire due to excess primary current as a result of core saturation. The audible hum is the iron core protesting about being driven into saturation 50 or 60 times per second. > Either I misconstrued your comment ** You did. > or I must have been sleeping in my EE101 > electric machinery course years ago. ** Maybe you were - but the behaviour of a transformer subjected to an asymmetrical current load is rarely mentioned in elementary texts. > John Wood (Code 5550) e-mail: wood(a)itd.nrl.navy.mil > Naval Research Laboratory > 4555 Overlook Avenue, SW > Washington, DC 20375-5337 ** Hmmmm - sounds kinda serious like ...... ........ Phil
From: John Woodgate on 15 Aug 2006 09:43 In message <wood-1508060711270001(a)jbw-mac.itd.nrl.navy.mil>, dated Tue, 15 Aug 2006, J. B. Wood <wood(a)itd.nrl.navy.mil> writes >Hello, and direct current in the core as a result of current flow in >the secondary windings? Not direct current but DC magnetic flux. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk 2006 is YMMVI- Your mileage may vary immensely. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
From: John Popelish on 15 Aug 2006 10:41 J. B. Wood wrote: > In article <-M2dnYH0Js-9cH3ZnZ2dnUVZ_r6dnZ2d(a)adelphia.com>, John Popelish > <jpopelish(a)rica.net> wrote: > > >>In addition to the filter and secondary current comments: >>If you don't load the two outputs equally, there will be Dc in the >>transformer core, causing it to saturate at the end of alternating >>half cycles. It will hum and get hot. > > > Hello, and direct current in the core as a result of current flow in the > secondary windings? Just how would that be possible? Is the core part of > some external circuit? If you mean eddy currents they would be AC and a > power transformer core is laminated to minimize this effect. Either I > misconstrued your comment or I must have been sleeping in my EE101 > electric machinery course years ago. Sincerely, I have been waiting for this. I misspoke. There is no current in the core (except for the normal AC eddy current). I meant to say that there will be a net DC in the windings, which will cause the core to magnetically saturate at the end of alternating half cycles.
From: joseph2k on 16 Aug 2006 21:35
Jim Thompson wrote: > On Mon, 14 Aug 2006 08:48:42 -0700, Jim Thompson > <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote: > >>On Mon, 14 Aug 2006 10:11:21 GMT, joseph2k <quiettechblue(a)yahoo.com> >>wrote: >> >>>Jim Thompson wrote: >>> >>[snip] >>>> >>>> I said it was silicon. The Ge device I used in HS was a Delco >>>> doorknob power device. I did 10W class-A ;-) >>>> >>>> ...Jim Thompson >>> >>>OK. You have used a "doorknob" power device. What the heck did it look >>>like? Where can i find outline drawings? You are about the third person >>>i have heard admit of their existence. >> >>I probably have an appropriate data book around here somewhere. I'll >>look for it. >> >> ...Jim Thompson > > See.... > > http://analog-innovations.com/SED/2N1358.jpg > > ...Jim Thompson Thanks a bunch. Never knew that is what doorknob is. I have used a few also, a long time ago (30 years +). -- JosephKK Gegen dummheit kampfen die Gotter Selbst, vergebens. --Schiller |