Re: [CAD_CAM_EDM_DRO] Power Supply Question - a bit OT

On 11/1/01 9:16 PM, "Jon Elson" <elson@...> wrote:

> Brian Walsh wrote:
>
>>
>> I have a requirement to deliver 2000 Amps or so at about 30 or 40 volts AC
>> or DC into a load. The load is made of stainless steel wire and is basically
>> resistive with a 'smallish' positive temperature coefficient.
>
> That's 60 - 80 KW! Do you have that much power available?
>
>> At this stage the precise current requirement is unknown, so the ability to
>> adjust the current is desirable. There may also be a need to control the
>> current / time profile, as the particular requirements of the process become
>> apparent.
>>
>> My immediate solution to this is to take ten 200 amp, cheap, arc welding
>> units and connect their outputs in parallel. This is clearly not their
>> intended mode of operation, so I don't imagine that the manufacturers will
>> be prepared to comment on their suitability to this use.
>
> If the units are identical, and you can be sure they are wired exactly the
> same, it should sort of work, but it sounds like a nightmare. At least, the
> arc
> welders won't explode when short circuited.
>
>> Is anyone here willing to venture an opinion as to whether or not simple
>> (reluctance controlled - I assume) arc welders can be combined in parallel
>> to achieve high current outputs? Will they current share, current hog,
>> trip-out, explode?
>
> As long as they are all phased the same way, they pretty much HAVE
> to current share. If one of them has the phase wired backwards, all bets
> are off. This also means every outlet for the 10 welders has to be wired
> with the same phase, which the electricians would not do unless you
> tell them is has to be that way.
>
> Jon
>

Brian:
You might take a look at some of the graphite furnace power supplies used to
resistance heat furnaces for atomic absorbtion. Rumor has it they make dandy
welders...some are three phase 240 with (maybe 40 A ) plugs. The connectors
are special and I'm told they grip better when current runs thru them. They
are made for intermittent duty though; the typical load only is on for a few
seconds.
The ones I'm thinking about are years old at this point and were made by
Perkin-Elmer. If you need more information e-mail me off list....but use
dsengvall@....

Dave