In the late 1980’s, we had some cubicle wiring fires at HP Labs caused by computer power supplies. They had to replace all the wiring with bigger conductors and connectors for the neutral. The same thing happened with Project Athena at MIT.
wunder K6WRU Walter Underwood [email protected] http://observer.wunderwood.org/ (my blog) > On Aug 11, 2016, at 1:09 PM, Jim Brown <[email protected]> wrote: > > On Thu,8/11/2016 12:03 PM, Lewis Phelps wrote: >> So, why go to the extra expense of #6 wire? > > All the calculators assume sinusoidal current (i.e., a perfect 60 Hz sine > wave). That's not the real world -- only un-controlled heating elements draw > sine wave current. For at least the past 30+ years, electronic loads > dominate, and the what's connected to the power line is a > transformer-rectifier-capacitor power supply, and now usually as the input to > an SMPS. The line current drawn by such a supply takes the form of short > pulses at positive and negative peaks of the 60 Hz waveform, so both IR drop > and dissipation is much greater than predicted by simple sine wave analysis. > None of this is taken into account by NEC. > > Thus, it IS good engineering practice to oversize AC conductors. > > There's a tutorial discussion of this in > > http://k9yc.com/GroundingAndAudio.pdf > > 73, Jim K9YC > > ______________________________________________________________ > 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 > Message delivered to [email protected] ______________________________________________________________ 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 Message delivered to [email protected]
