> > On Jun 30, 2007, at 3:23 AM, Vasile Surducan wrote: > > On 6/29/07, Cedric Chang wrote: >>> >>> On Jun 28, 2007, at 2:07 AM, Vasile Surducan wrote: >>> >>> On 6/28/07, Cedric Chang wrote: >>>> >>>>> On Jun 27, 2007, at 10:06 PM, Vasile Surducan wrote: >>>>> >>>>> The key is not only the winding number/cross section (which is a >>>>> problem of mechanical power versus efficiency) but the presence >>>>> of the magnetic flux amplifier (brass tube as a support for >>>>> windigs) and >>>>> an end of the slug made from brass with a cone shape and perfect >>>>> match into the >>>>> negative cone of the ending brass tube. >>>>> >>>>> Inspire yourself from a high power DC relay design. The >>>>> efficiency of >>>>> such construct is huge compared with a poor iron slug. >>>>> >>>>> Vasile >>>>> >>>> Why brass ? >>> >>> Because it concentrate the magnetic field. >> >> I looked on the web and most folks said to use >> ferromagnetic materials such as steel for the >> magnetic flux concentrator. >> >> http://www.ee.surrey.ac.uk/Workshop/advice/coils/mu/ >> http://www.ndt-ed.org/EducationResources/CommunityCollege/Materials/ >> Physical_Chemical/Permeability.htm >> >> These indicate that brass is a bad choice. >> >> Did I miss some important info ? > > "Concentrating" the magnetic field is an english word with many > understandings. > Imagine a coil which must be perfect isolated from the rest of the > world. > The perfect cage will be a sandwich manufactured from: > - one layer of permalloy > - one layer of copper > - one layer of permalloy > - one layer of copper > - one layer of permalloy > > I think the explanation for brass magnetic field "concentrator" is > the same. > There is an electric and a magnetic variable component even in a DC > magnetic field > (because always there is a switching moment). The magnetic component > is concentrated using ferromagnetic materials. The electrical > component must be converted by conductive material as brass or copper > instead of being lost. And the electric component is quite huge on > huge current or large inductance coils. > I'm still searching for that coil, the plans dissapeared in the 16 bit > windows era, but I remember I still have one... > > Vasile Excellent I understand Cedric > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist