"Ignoramus18928" wrote in message
.. .
On Sun, 25 Sep 2005 20:21:28 +0100, Moray Cuthill
wrote:

"Ignoramus18928" wrote in message
...
I am confused. The nameplate on my hobart cybertig says that at 230V,
it consumes 44 amps.

http://igor.chudov.com/projects/Weld...r/dscf0003.jpg

Absent the power factor number, that means roughly 220*44*sqrt(3) = 16
kW power consumption.

Yet, it is a 28V, 200A welder, which means approximately 6 kW power
output.

How can I reconcile these numbers? How can it take in 16 kW and yet
only produce 6 kW? That seems awfully wasteful.

I tried to estimate what it would take, assuming more reasonable power
efficiency.

It if produces 6 kW and wastes 2 kW as heat, then it would need 8 kW.
Estimating amps, 8 kW/220/sqrt(3) = 21 amp.

This is not an idle question for me. I have 3 phase cabling that is
capable of conducting 21 amps (combo of a 12 and 10 gauge cables). For
44 amps, I would need to spend big bucks to buy 4-6 flexible cable.

Also, I can easily support 8 kW power consumption after adding an
extra idler to my RPC. 16 kW is out of my realm of possibility due to
branch circuit capacity and common sense.

Some clarification would be appreciated.

I always thought the rated input current was the peak current (ie when
you
initially strike an arc), with the rated output being the continuos
current?

That makes sense... So, what would realistically happen if less power
was available to the welder, enough for continuous welding but not
enough for, say, rated starting power usage?

IFF that is true, then you'd proly just have more trouble starting yer arc,
it would seem to me.
Power factors always confused me, but the bottom line can be solved w/ a
relatively inexpensive AmpProbe, or clone. Clamp it on, see what it sez.
Def'ly a tool you should own, Ig, considering your interests.

Ito of your wire size, it all depends on the *length of the run*.
For a short run, and given that most welding is done in spurts (given 20%
duty cycles), #12 wire is proly good for 50 amps, esp. if 'exposed" (ie, not
crammed into pipe w/ 30 other wires).
Purists here will squawk like hell, but take this in context of the caveats
I mentioned. #12 wire can *easily* handle 30-40 Amps continuous, mebbe
getting a little warm.
Not recommending it, just saying you can get away with it.
So your 10/12 ga combos are proly more than adequate, if you run is not much
over 60 feet.

You can tell the effect of length on voltage drop w/ a simple bulb hooked up
to one leg, or w/ a voltmeter. I think a voltage drop of 10% is tolerable ,
if electronics are not too persnickety.
Ito of your rpc, the voltmeter will also be a good guide.

The Ampprobe is interesting as you watch it, relative to the types of arc
you strike. You can also put the ampprobe on the welding cable itself, to
see how the arc affects things.

If you are able to control things mechanically (arc stability, length, etc),
you can "verify" the nameplate for yourself, using sed amp probe/voltmeter,
ie, comparing the input/output kVA ratios you actually measure.
----------------------------
Mr. P.V.'d
formerly Droll Troll



i