Gabriel Gonzalez wrote:

>I need to pass 40-60A thru a wire to insure the capacity, but where do I get
>this much current without having to use a humungous load to drop the voltage
>and control the current.
>
>I thought on using a relatively large power transformer, replacing the
>secondary winding with a few turns of really heavy gauge to get a low
>voltage (0.5-1V maybe) at a high current.

Exactly what I use.  I have on old spot welding transformer that puts out a
couple of volts unloaded and about 300 Amps shorted.  I use a variac to
control the primary if I am unsure of the resistance of the load.  For
repetitive tests, I replace the variac with a series light bulb of
appropriate wattage to give me the output current I need.  Note the light
bulb is in series with the Primary of the transformer.  It acts like a
ballast resistor and quasi-regulates the output current.  Sometimes I drive
the transformer / bulb combo from a variac.

Note that spot welding transformers are intended for short duty cycle use if
driven near full power.  I find that I can get about 60 -70 Amps continous
out of mine without the transformer getting too hot to touch.  Go anywhere
near the full rated current on a continous basis and you WILL generate a lot
of smoke and a bad smell.

Hope this helps.

dwayne


Dwayne Reid   <dwayner@planet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(403) 489-3199 voice     (403) 487-6397 fax