Hi, I have a 10KVA 3 phase generator, i want to use a welder with this generator but its not working properly?

The wiring is done so that the single phase power supply is just one of the 3 phases. Am i correct that this single phase/line is 3.3KVA ?? and, is ir possible to wire the 3 phases together to give me 10KVA (or higher than 3.3KVA) SINGLE phase power?? It seems that the welder is not getting enough power...??

Answer:
Certain 3-phase generators can be rewired to operate as single phase. If the alternator has 12 wires, you can reconfigure the system for 120/240V single phase. The maximum output power will be reduced to 6.6kVA at 240V. Maximum power available from each 120V line remains 3.3kVA.

Here is a picture I sketched earlier to show how this works. It is clearly not to be used as instructions for you to rewire your generator.
http://members.rennlist.com/warren/3-pha...

You could also wire the system for 120V single phase only. In this mode, maximum power would be 6.6kVA.
If you get single phase output by connecting to one phase and neutral, you get 58% of the line to line voltage and 3.3 KVA. If you connect to two of the three phase output, you get the line to line foltage and 5.8 KVA. If both ends of each of the three phase windings is accessible, there may be a way to connect them in series and get a higher voltage single phase supply.

Re additional info
If you connect the proper voltage to the welder, it should take whatever current it needs. If that is too much for the generator, it will blow a fuse, pop a circuit breaker, overheat, make the engine slow down or otherwise not work properly. What is the voltage rating of the generator and the welder? If the generator has terminals labeled A, B & C or L1, L2 & L3, those are 3-phase terminals. Any two of those will provide single phase power at the 3-phase voltage rating and 5.8 KVA. If there is a neutral terminal, probably labeled N, there will be 58% of rated voltage between that terminal and any one of the other 3. Bridging any of the 3 wires will make a short circuit. The frequency will always be 60.
here's some computation for you:
For a 10 kva , 3phase assume voltage=220 volts
Total current : I= 10*1000/1.732*220 =26.24 amps, this is the total amps you can load on any phase of your genset.
so if you load a single phase on any leg, your maximum single phase load would be:
KVA= 26.24*220=5773/1000= 5.773 kva
note; never short any terminals of your genset in it's terminal box, it will go up in smoke :(
also; don't just divide by three the per phase kva of the 10 kva winding, there are two ends of windings connected on that line if it is delta connected, two windings will be used too if wye connected, only one winding if there is a neutral that you'll connect to, plus one line of the generator.
If you have a 10 KVA generator and are using 240 volts, then the maximum current that your welder can draw is 10,000/220 = 45.5 amps.
If your welder requires more then 45 amps, then you don't have enough power.
At 120 volts you can generate 90 amps.

My 6.5 KVA generator is rated at 27 amps at 240 volts, and 54 amps at 120 volts. I use a 4 prong receptacle rated rated at 30 amps. Either 120 or 240 volt loads can be powered thru this receptacle.

The receptacle has 1 ground (green) plug, 1 neutral (white) plug, and 1 "x" (hot), and 1 "y" (hot) plugs.
The output is 120 volts between neutral and "x" and 120 volts between neutral and "y".

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