[Elecraft] KPA-500 110 or 220?

[Jim Brown]

On 8/6/2012 11:59 AM, Monty Shultes wrote:
>   "I-squared R drop",

I'm sorry, but you are mistaken. Voltage drop is IR.  The POWER lost in 
the resistance of the wire is I squared R.

To complicate things even more, the current drawn by any power supply 
with a capacitive input filter is a pulse, not a sine wave, so the power 
is the INTEGRAL of the current squared. The current is a pulse because 
it must recharge the filter cap on each cycle, and most of the current 
flows at the positive and negative peaks of each cycle.

The impulsive nature of the current causes the 60 Hz sine wave to be 
distorted, creating harmonic distortion. That's why power line leakage 
current is heard as "buzz" (the harmonics of 60 Hz) rather than "hum" 
(pure 60 Hz).  AND the impulsive nature of leakage current increases the 
power lost beyond what would be predicted by simple Ohm's law applied to 
a 60 Hz sine wave -- there's much more power lost at the peaks of the 
charging cycle.

73, Jim K9YC