Ah, my bad. I was transmorgafying the limitations of peak voltage which can allow greater power delivery on DC lines than AC. That is, a 240 VAC line has peak voltages of 330 volts. As the voltage rating of the line becomes an issue, then a DC line can operate at that higher voltage and deliver 1.4 times more power than the AC system while keeping within the maximum voltage spec. (ignoreing transients of course)..
So you are right. Argument does not apply here since most wiring is rated at 600 volts well above the 240 VAC peaks. Bob -----Original Message----- From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of Roger Stockton via EV Sent: Wednesday, June 08, 2016 3:21 PM To: Electric Vehicle Discussion List Subject: Re: [EVDL] Off-grid solar house and electric car charging Robert Bruninga wrote: > Yes, as far as VOLTS and as AMPS as averages are concerned. Such as > average power. A 1500W resistor will be 1500W whether on DC or RMS AC. > > But the power loss in wires feeding that resistor will have greater > loss on AC because of two factors important in distribution systems: > > 1) SKIN EFFECT where the AC current is pushed to the outside of the > wire so that not all the wire is carrying the same current. Thus the > wire is not as effective since not all of its copper is being used in > an AC system The skin depth in copper at 60Hz is 8.47mm; this means that until you are using a conductor with a diameter greater than 2 x 8.47mm = 16.94mm (about 0.67"), the AC resistance is the same as the DC resistance. <https://en.wikipedia.org/wiki/Skin_effect> > 2) Peak power losses. As you note, the RMS current is the same, but > the PEAK current is 1.4 times higher during the peak of the waveform > and since that is where the most power is delivered that is also where > the most loss occurs in the wire. So the average power lost in the > wire for AC is almost twice (1.4 squared) the loss in the same wire at DC. > > Google it... "For a cyclically alternating electric current, RMS is equal to the value of the direct current that would produce the same power dissipation in a resistive load." - <https://en.wikipedia.org/wiki/Root_mean_square> Cheers, Roger. _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
