Calculating the amount of capacitance needed to reduce the idle current
is actually fairly simple. I have posted how to do it at least twice.
Try seaching on google with "power factor correction "

What you do need to remember is that you really don't want to correct
to more than about 85% power factor. Correcting for that last 15% will
not change the idle current very much.

Okay, I will post this one more time. First measure the current drawn
with the welder idling and no power factor cap. Now add a power
factor cap right across the line in parallel with the welder.
Measure the current again. Now for the graphic solution. Use a
compass and swing an arc that is proportional to the first measurement
from point A. Shorten up the compass and swing a second arc ( also
from point A ) proportional to the current with the P.F. cap
installed. Now subtract the second current from the first current and
set the compass to this length. Now put the point of the compass on
the first arc and swing an arc so it intersects the second arc. Draw
lines from point A to where you had the compass on the first arc and
from point A to where the intersection is with the second arc. DRaw a
third line between the ends of the two lines. Now turn your drawing
around until that last line is vertical. Draw a line from point A
horizontal to underneath the vertical line. Extend the vertical line
to the horizontal line.

Okay? The horizontal line from point A to the vertical line is the
amount of current that is real. The vertical line is the imaginary
current. The length between the two arcs is how much imaginary current
flows through the P.F. cap. The line from point A anywhere on the
vertical line is the total current. Note that doubling the imaginary
current ( doubling the capacitance ) does not double the reduction is
the total current.

This is not easy to explain. So measure the current with no P.F. cap
and with a P.F. cap installed and post the results and I will do the
graphics and tell you what I get for results.

Dan




Gunner wrote:
Any idea of how to calculate the amount of capacitance needed to
reduce idle current in a single phase 220 welder?

Gunner, Idealarc Tig250/250 and Miller Dialarc 300


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