Roger Stockton quoted: "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>
Roger, You used the wrong definition. The Wikipedia quote is about the power delivered to the *load* but the discussion was about the power losses in the *wire* feeding the load. The situation is the same problem as with (bad) Power Factor: even though the average power delivered to the load with bad power factor is the same, the short and high spikes of current will heat the wires more than in the case of a good power factor, simply because the loss in the wire goes with the current squared, so higher peaks (and equal *average* current) still results in higher losses in the line due to the squaring of the current peaks in the formula for the power loss. To use a simple and somewhat excessive example as illustration: Case A: DC power to an (arbitrary) load: 1 Amp continuous, 1 Ohm line resistance so 1 Volt drop, meaning 1V * 1A = 1Watt of loss in the line. Case B: power provided with 10% duty cycle so 10A during 10% of the period and 0 during 90% of the period. Average current still 1A and same power delivered to the load as in case A. However, the line load is still 1 Ohm so the 10A current causes a 10V drop and thus 100 Watt power is lost in the line during the 10% that the current is flowing, the average power loss in the line is therefor: 100W * 10% = 10W so the average power loss in the line is 10 times as high as in case A due to the peak current being 10 times as high, even though it is only flowing 1/10th of the time. (Note that in case B it is claimed that the same power is delivered to the load, so this means that the extra power loss in the line must be delivered by a higher power draw from the source, we are after all dealing with physics here) Regards, Cor. _______________________________________________ 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)
