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.

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