David, et al, I just learned that a toroid core is wound from a single strip of metal, like a coiled clock spring, one continuous piece. But whether this one is welded, I cannot say. My guess is probably not. As for impregnation, I do not think so. The construction details I saw describe core, core caps, insulation layers, winding wires, and the core potting material. Nothing at all about varnish or impregnation. The windings are covered with an overall insulation wrap so I cannot see how tight they may be. These are all interesting questions and we will be talking with the vendor after the first of the year to go over these and other construction details.
Roger McCoy raises the question of the center bolt being a shorted turn since it passes through the core and electrically connects to the metal box on either side of the transformer. That box surrounds the core just like a winding turn would do. My question is, is it usual practice to isolate this bolt electrically from the metal chassis, say by a fiber or plastic washer? The bolt is certainly isolated electrically from the core and windings by the core potting material. Once again, I am amazed at the depth of the discussion this list can generate. My heartfelt thanks to all participating. Merry Christmas and Happy New Year! Scott David Greig wrote: >I should have added that the most probable cause of noise besides lamination, is the mmf between loaded windings. > >Are the windings tightly constrained or impregnated? > >Best Regards > >David Greig > >-----Original Message----- >From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of David Greig >Sent: 22 December 2005 11:58 >To: drcuthb...@micron.com; j...@jmwa.demon.co.uk >Cc: christopher.col...@harmanpro.com; emc-p...@ieee.org >Subject: RE: What Makes A Transformer Hum (continued) > >Is the lamination stack welded? > >This could provide a outside rigid axis for the laminations to "pivot" against, given that any impregnation will be more >compressible than the weld. Welds may also distort the stack. > > >Best Regards > >David Greig >______________________________ >GigaDyne Ltd >Buchan House >Carnegie Campus >Dunfermline KY11 8PL >United Kingdom >t: +44 (0)1383 624 975 >www.gigadyne.co.uk >______________________________ > > ><< snip snip >> > > > - 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 emc-p...@ieee.org 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 emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
