Join Date: May 2002
Location: East Coast
Thanked 6 Times in 6 Posts
Rep Power: 18
EBS...AHAH!! I've found the answer I think to what you were talking about with reactive/inductive loads. Looking at the manual for the 45amp charger I found an interesting spec...it said:
Max WATT DRAW...842.4 (VA watt draw 1296)
Note this is remarkably close to the numbers we've been discussing where VA watts would be MY measurement and the 842.4 number would be close to the 80% efficiency number! Note the RATIO is 65% between the two numbers.
Doing some research on VA watts vs. Watt draw...I came up with these statements:
VA in AC circuits is "reactive power" and has nothing to do with real power.
Loads such as induction motors, do not act as pure resistors, but like
inductors. Inductors and capacitors draw AND supply power back into their
power source. Induction motors supply current BACK into the power grid ever
half cycle. These currents tend to somewhat cancel out, but are still there.
If I supply 10 amps on a wire for 1 second, then reverse the polarity and
try again, the net current flow from end to end was zero, but 10 amps were
flowing for 2 seconds.
It would seem that
the volt-amp refers to the maximum power flow, while the Watt refers to a
time-averaged power flow. In AC circuits, Power flow varies as a sine
function. The "root-mean-square" rate of flow is approximately 65% of the
Mystery explained! Your instincts were correct!! Thanks.
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