On Jan 25, 2011, at 1:02 PM, Jim Brown wrote: > On 1/25/2011 10:37 AM, Scott Ellington wrote: >> but my AL-82 once blew the 15 A 240 V fuses, which suggests PF was less than >> about 0.7. > > More to the point, the main thing that blows breakers with very large > power supplies is the inrush of current at turn-on to charge the input > filter cap.
Not in this case. Anyway, the AL-82 has inrush current limiting. > > The difference between a linear supply and a switching supply in this > regard is that while they both have input filter caps, the cap in the > linear supply is much larger (and the transformer is usually more > robust), so the inrush current will usually be greater. Not necessarily. Many switching supplies simply rectify and filter the line voltage to produce 170 or 340 V DC, without even a transformer to limit the current. (All now have at least a thermistor, but they didn't always.) More expensive switching supplies have power factor correction circuitry, which inherently limits inrush current. I don't know that any of the switching supplies commonly used to power transceivers have this feature. (Virtually all computer supplies do, as required by law. How this came about is an interesting story.) 73, Scott K9MA Scott Ellington Madison, Wisconsin USA ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
