Simple Power Supply Stuff

[gstopp at fibermux.com]

     Oh okay the resistors were dummy loads - for some reason I got the 
     idea that they were part of the design! Sorry, got confused. I've been 
     hanging around switching supplies too much, I guess.
     
     Anyway about resistor power ratings - if you run 10 watts through a 10 
     watt load resistor, it will glow red hot! Resistor power ratings are 
     intended to describe the absolute maximum operating parameters. In 
     fact the reason that you usually see spade lug connectors crimped onto 
     power resistor terminals is that soldered connections might melt! 
     (Been there done that, much sparks.) If you run 1/4 watt through a 1/4 
     watt resistor, by golly that will make a little hissy noise when you 
     touch yer finger to it too. So I'm not surprised that 5.6 watts 
     through a 10 watt resistor gives off some stinkey heat waves. Don't 
     worry - sounds like everything is working like it should.
     
     - Gene
     gstopp at fibermux.com


______________________________ Reply Separator _________________________________
Subject: RE: Simple Power Supply Stuff
Author:  Bob Zimmer <bzimmer at voicenet.com> at ccrelayout
Date:    7/2/96 1:27 PM
     .
     .
     .
  The 11.25W is definitely too much for one 10W resistor, but with the pair,
  I was expecting that each resistor would be dropping 5.6 Watts, which should 
  be within their 10W rating.
     
  Why isn't this true??  I can't find an explanation in my electronics books.