[Elecraft] KPA500 transformer taps

[Jim Brown]

On Thu,6/1/2017 9:41 AM, Phil Kane wrote:
> As Josh said earlier, be very concerned about the10 volt drop in the AC
> voltage measured at the load.

All great advice. Also, try to trace the wiring that feeds the outlet 
that the amp is plugged into. Possible causes of the high voltage drop 
are 1) conductors that are too small (AWG #14 is the smallest permitted 
for a 15A circuit, #12 for a 20A circuit); 2) bad splices; 3) miswiring 
of outlets or splices (reversals of hot and neutral, or hot and ground, 
or neutral and ground); 4) degraded outlets; 5) miswiring of the KPA500 
power cable (like #3).

For a circuit carrying this much current from an electronic load, wiring 
should be a direct run of #12 (hot, neutral, and ground) from the power 
panel to the outlet. While #12 is not legally required for a 15A 
circuit, the larger conductors reduce IR drop.

AND -- load current to electronic loads is NOT a sine wave, but instead 
consists of pulses at positive and negative peaks of the waveform to 
recharge filter caps in the power supply. This causes IR drop to be 
greater than predicted by application of Ohm's Law to a sine wave. SO -- 
it's good engineering practice to oversize conductors on circuits for 
electronic loads. Two wire sizes is a good rule of thumb.

73, Jim K9YC