[Boatanchors] RE: More question on US AC voltage

[Dave Maples]

All: Whether or not increased line voltage causes a power increase depends
on the load.

If the load is resistive, then as was illustrated earlier an increase in
voltage = an increase in power.

If the load is a combination of resistance and reactance (typical motor
load) then increasing voltage again results in an increase in power.

If the load is a linear power supply (regulated or not) then the same thing
applies.  Even though the output voltage of the regulated linear supply
stays constant, a linear supply operates by dissipating power in a pass
transistor or similar.  If input voltage rises, the pass transistor will
absorb more power.

HOWEVER, modern electronic appliances (not motors or incandescent lamps)
typically use switchmode supplies.  These ARE constant-power devices, so as
the input voltage rises or falls (within the specified voltage range of the
supply, of course), the input CURRENT changes in an INVERSE fashion to
compensate.

The percentage of load that is made up of switchmode supplies is still a
small fraction of the total electrical load of the typical residence or
business, so the original idea (increased voltage = increased revenue) is
correct as far as it goes.  However, I suspect that the more accurate reason
for doing this is that the electric power infrastructure cannot keep up with
demand.  Raising voltage is a relatively easy way to cope with the increased
power demands in older neighborhoods, as far as I can see.

Dave Maples