Varying a high current low voltage power supply cheaply

[Aether]

The power supply is only about 3 volts but hundreds of amps, it will have been passed through bridge rectifiers but can be modified while it is still ac. I know all about the laws of resistance and everything. Why I'm wondering is what is the cheapest way to using a knob vary the current and still be able to Handle it. The king of random created a model which did exactly what I want however it was to big for my liking, I want something small. I find it very unlucky but is their a potentiometer or something that can handle this amperage?(doubt it it works probably melt) and since its such a low voltage the resistance would have to be very small. Any ideas?

 

[duke37]

Where does the power come from?
What does the power go to?

Phase angle control of AC input could be used but may run into transformer saturation problems.
You could put a bridge rectifier in series with an AC supply. When this is shorted across, it will drop little volage. A controlled transistor with a large heat sink could vary the output.

If the power is large, it will not be small.

Why are you asking us if you know everything?