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Registered Member #4266
Joined: Fri Dec 16 2011, 03:15AM
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Posts: 874
Been looking around for high amp sources and I have a arc welder, which they can be picked up quite cheaply.
What would the effect of running this throught a large copper cable, with theac changed to a bridge, would it have any negtive effects on the welder been a short, would the voltage stay at around 20-40 volt or drop sshorted throught a copper wire.
Any ideas that might effect it that I havnt thought of, welcomed
Registered Member #42796
Joined: Mon Jan 13 2014, 06:34PM
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Posts: 195
you have to apply Ohm law....
in a short circuit case or for a very small resistance for a REAL power source the voltage will always drop to about 0V and the current will be maximum
Registered Member #3215
Joined: Sun Sept 19 2010, 08:42PM
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Posts: 780
correct, but an AC arc welder will not necessarily be current limited, while a good SMPS with built in limiting and conservative ratings will deliver all those amps without burning after a couple minutes
you could always use rewound MOTs and a kind of phase angle switching to limit current
Registered Member #42796
Joined: Mon Jan 13 2014, 06:34PM
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Posts: 195
Shrad wrote ...
correct, but an AC arc welder will not necessarily be current limited, while a good SMPS with built in limiting and conservative ratings will deliver all those amps without burning after a couple minutes
yes it can deliver all those amps but the voltage will in no way be the same as the rated supply voltage....
in the case of a server psu yes it can deliver 70A and keep the voltage constant but only to a proper load if a short occurs the psu can't deliver 70A while keeping the voltage constant (again Ohm law) and it will stop
Registered Member #3215
Joined: Sun Sept 19 2010, 08:42PM
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if you use a simple transformer without current limit, it will overheat
if you use a SMPS within its ratings you should be able to get big current as soon as your load impedance is not too small and resembles that of a server
Registered Member #816
Joined: Sun Jun 03 2007, 07:29PM
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Posts: 156
Consumer grade arc welders, I don't think are rated for 100% continuous operation. They expect time to cool down between welds. So you would have to de-rate them.
The voltage regulation probably wouldn't be that good. They may be 50v on low load and drop to half that on full load. Good thing is they probably will stand a lot of abuse, And yes be short circuit proof for a short duration, until a thermal cutout kicks in.
Not sure if I've understood correctly but if you are just trying to power a large coil of wire, like an inductor or electromagnet, You only need enough voltage to overcome the d.c resistance of the coil to generate the current you require, plus what you drop across the rectifiers.
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Arc welder as a amp source
