Sorry but you are wrong with respect to current/horsepower going DOWN at
high pressure. most air compressors are positive displacement
(piston/diaphragm type) machines for which power goes up as discharge
pressure goes up. There is rule of thumb in the Hydraulic Institute
Standard that give the formula. Vacuum cleaners are on the other hand are
centrifugal compressors where at free flow (open suction and discharge fully
open) power consumption is the highest.

--
Larry
"Greg" wrote in message
...
An air
compressor does not draw full load when it first kicks in (excluding
initial
startup inrush). The current climbs as the pressure in the tank
approaches

I put a Fluke clamp on to my compressor and the reality is it pulls the
most
from about a fourth to half way through bringing up the tank pressure.
This has
to do with the bite of air it gets to compress, When it is close to the
max it
is throttled and doesn't take in much air. That is similar to a vacuum
cleaner
with a plugged hose. It actually runs faster at lower current because
there is
less load.