How much power does a welder use

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I have a Kemppi Master 1400 Stick welder that I'd like to be able to use
aboard my boat
I have a 2400w inverter fitted that I think is a square wave, might be
modified square wave.
or... I do have access to a 3.5kv generator. would either of these run it.
The Kemppi has a maximum output of 140amp, but at what is the voltage, how
many watts do I need to strike the ark etc

thanks





Re: How much power does a welder use
The Generator would run your welder, but the Inverter would only be able to
handle it if you were charging your battery bank at the same time. I have a
2000watt inverter and 800 AH battery bank and I know it would be pushing my
capacity.

Just an Idea! The off-roaders, have little welders that they run off their
alternators  for back woods welding repairs. Maybe these are specially
modified alternators. All I know is that my son has one on his off-road
Toyota.

Steve
s/v Good Intentions


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Re: How much power does a welder use
Welder typically runs around 25 volts while welding (open circuit
voltage is a different story) with reasonable efficency. That would put
your max power at around 4kw. But you can do nice stick welding of 1/8"
6013 at around 110 amps, 3/32" at 80 amps. Depends on what you are
welding. Big problem is when you stick the rod, it pulls the full
amperage setting.

I did a quick search, it's not clear if the Kemppi is an inverter unit
or a transformer unit. (If it's heavy, it's a transformer!) I would NOT
want to feed an inverter welder off of a square wave inverter, too much
chance the circuits will start fighting each other. A transformer welder
MIGHT work on an inverter, depends on how well the inverter takes to the
heavily reactive power factor as well as the inductive surges you will
see. Net: I don't think I'd chance it on your inverter, even at low power.

I run both a 120 volt MIG welder and a 225 amp (dialed down of course!)
AIRCO stick welder off of a 5kw generator. Works ok, either one will
load the generator quite heavily.

Nigel wrote:
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Re: How much power does a welder use
You can get a welder that operates directly off of lead-acid batteries
and (reportedly) works well.  I'm too lazy this morning to google it
for you.
Paul Mathews

RoyJ wrote:
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Re: How much power does a welder use
Ready Welder
http://www.readywelder.com/11000.htm

Paul Mathews wrote:
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Re: How much power does a welder use
Thanks all, for your advice
I found Kemppis address and emailed them,
I got a reply back in a few hours, I'm impressed with their aftersales
service (even if it wasn't what I wanted to hear)

------------------------------------------
From the rating plate on this machine, the mains supply is norminal value is
1phase 230v ( 198v - 254v)
the rated fuse is 16amp slow blow
The input current is proportional to the output value set on the current
dial.

At max output the power is 6200 VA  (6.2Kva) power factor 0.75 therefore
output power in watts is 8267 watts
At 75 amps output the power is 2900 VA so an estimate of power in watts (pf
approx 0.6) is 4833 watts

Therefore we would NOT recommend using your battery/inverter supply to power
this equipment
 because of the in-rush and surge currents even at the low output and using
1.6mm electrodes.

The generator supply is probably also not large enough, unless it has a very
well  regulated output, again due to
the in-rush and surge currents even at the low output and using 1.6mm
electrodes.

We recommend a minimum generator of 6.2Kva.

Best Regards
Martin Forster
Service Technician

Kemppi UK Ltd
_________________________________________________



Re: How much power does a welder use
Nigel wrote:

<Of welders>

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You have that backwards!
6.2KVA @ 0.75PF is 4.65KW, but is still 27A@230V.
2.9KVA @ 0.6PF is 1.74KW, but is still 12.6A@230V.

Use the VA number to calculate the load current, and multiply VA by power
factor to get real power.

Note that the PF will probably be lagging in this case and you will need to
be careful about the inverter ratings....

Note also, that the VA rating determines the minimum current that the supply
must be able to source, but the real power determines engine size. It is
quite possible to have a very large alternator driven by a small engine
which will give a spuriously high current rating for most loads.  

You could always just hook the electrodes up to some of that battery bank
(reconfigure it to give 24V or so), and weld that way (BTDT), it does work
to get you out of a tight spot!

Regards, Dan.

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