DC for variable-speed has been largely supplanted by ac, multiphase motors over the last 20 years. There is ac-dc conversion in the front end of the controllers, but it is then followed by dc-ac single or, more commonly, three-phase, variable frequency generation. That's usually the source of the noise. The quietest (EMI) variable-speed drives are the ones that most closely generate a sinusoidal waveform. Since that costs money, most are kinda noisy. There are input and output line filters sold for variable-speed drives, and sometimes they are available on epay. Hitachi is one of the big manufacturers of VSDs that comes to mind.
73, geo - n4ua On Wed, Nov 10, 2010 at 3:40 PM, BOB PHILBROOK <[email protected]> wrote: > DC motors? BEt so if they are variable speed. > > If so, AC to DC conversion might be part of your source of RFI. > > Bob, K9PAG > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
