Re: 1 KVA 240 v transformer output 6v,8v,12 v AC how to test if it can supply 83 amps?


"Rob" <Rob@xxxxxxxxx> wrote in message
news:9dan519v051c2s45ji12aui8eolqatpcqt@xxxxxxxxxx
> Ok let me explain a little bit more.. on the front panel i have 2
> control knobs each one controls voltage and the second one is used to
> set a limit on the current...the digital display, displays the actual
> voltage and thel current in use..
>
> Today what i have done is the following .. The rear Positive and
> negative terminals i connected a piece of copper welding rod about a
> foot long its about 2 mm thick.. To me this is a dead short and i
> expected to be able to turn up the current so as to melt the copper
> rod... However all that happend was that at about 30 odd amps it
> glowed red and then the current gradually dropped to about 25 amps...I
> admit i am a total novice at electrics but i was sure it would have
> took more current than 30 amps...i was sure it would glow white hot
> and pop like a fuse?...I then cut the welding rod and tried it at
> about 3 inch long this time it glowed whiter at about 80 amps...at 5
> volts..Now i have to say im getting very pissed off!!!..So next i
> added to the rear terminals a 10mm bolt about 3 inch long .. turned up
> the current and i stopped as it went over 150 amps???.... didnt want
> to break anything so i stopped increasing the current...Now i am
> totaly baffled the PSU can supply at least 150 amps to a big bolt?...
> so why isnt it giveing that type of amperage thru my electrolyitic
> cell?...
>
> My final test was to use a car battery tester.. this consists of a
> large strip of bent metal in between 2 metal prongs.. which has a amp
> meter in between it can test 12 v and 6 v car batterys...you normaly
> hold the prongs on the battery terminal and the heavy metal strip
> gets very hot you can read the ammeter readings to see how good the
> battery is..the bent metal strip is coverd with asbestos *** to stop
> getting burnt..
>
> Well i connected this battery tester to the positive and negative
> connection while my Dad turned up the current control..we stopped the
> experiment at about 250 amps.. it was obvious the PSU was working?....
>
> So i am totally gutted have i just wasted a lot of money... on a PSU..
>
> Why ? wont the PSU supply lots of amps to my Cell?....I have read
> several patents...the Voltage on the cell ranged between 3.9 v and 4.5
> v? at several 100 amps?.. the electrolytic solution is a super
> saturated Salt solution..?... I have replicated the exact experiment
> yet it wont work?..So surley the PSU is faulty?... but yet if it is
> why did it supply 250 + amps in the battery test?.. is there some way
> i can force the amps out of the unit?...
>
> If the answer is yes I have wasted even more money .. what power
> supply do i actualy need?...I have had several knock backs with this
> project.. but this one as knocked me of feet..My friend's say i have
> to stop wasting money...but i will get another power supply if i have
> to...i wont be beaten...i will just go bankcrupt :)..
>
> Hope you can advise?...

For openers, your cell resistance plus all of the other resistances of the
wires, connections, etc., add up to more than 0.05 Ohms required to get 100
Amps at five volts. A power supply of this current capability will 'always'
have remote voltage sensing that allows you to sense the voltage at the
load bypassing the voltage drops of wires, terminals, shunts, etc. At the
output terminals of the P.S. look for a second connection on both the
positive and negative points labeled "sense" or "voltage sense" or some such
wording. Disconnect these wires from the output terminals and re-connect
them with extension wires directly to your load, resistor, welding rod or
cell making it a four wire connection. That way the power supply will
maintain five volts at the load and not somewhere else, up stream as it now
does. In doing this, I think you'll find much better performance with the
ability to deliver much greater current.

Another point: Any metal that gets hot, especially red hot, increases
markedly in resistance. This limits the current to some lower than expected
value. Light bulbs work this way. When cold, the resistance is low and it
increases to a high value when the lamp is operating which limits the
current keeping the lamp from blowing. I suspect that is why you had trouble
delivering higher currents into your rod resistances. This is the reason why
I suggested placing the resistance elements in water, to keep the increase
in temperature, and therefore resistance in check.
Bob


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