rectifier amp control

[thesmoothers]

When using a commercial rectifier how do you control amps? I see most units only have one voltage dial.
I know ohm's law, when resistance changes either the volts or amps has to change also, what decides weather the volts or amps will rise?

[Fibergeek]

More recently designed (in the last 15 years or so) commercial rectifiers can be operated in CC mode.

Like lab type power supplies; these rectifiers will have both voltmeters and ammeters, and controls for both volts and amps.

By Ohm's Law; any of the three terms (volts, amps, ohms) depends entirely on the other two, no exceptions, ever.

The equation for Ohm's Law, can be re-arranged three ways:

V = I x R
I = V / R
R = V / I

All three are equally valid.

[thesmoothers]

what is CC mode?

the voltage is controlled by a pot adjustable resister, what is the amp side controlled with?
the madness behind all this is why no one seems to know how the AMP dial on a power supply adjust the amps. I have a 5v-25a power supply i want to use for plating smaller parts. My 200amp chrome unit adj. 0-10v 0-200a but does not fine tune well. can you point me in the right direction on making controlls for it? I've read electronics books and have basic skills, i won't kill myself scouts honor

[Fibergeek]

CC means Constant Current.

If you do a search (the button at the top of the page) for CC you will find 5 threads dealing with it, you'll find about thirty more in the anodizing forum.

How the amp dial adjusts the amps is just like how the volt dial adjusts the volts, it changes the volts. Since you know Ohm's Law, you of course can see that since I = V /R; that when you increase V, I will increase, and when you decrease V, I will decrease. The amp dial sets the current (amps) you want to provide, and the PS changes the voltage by itself so that that current you set is what's flowing. Obviously, you need to have a load on the power supply (the R) to draw any amps.

An example:

Say you had a 0-30V, 0-5A power supply that could operate in CC mode. The current you want is say 2A. You put a 5 Ohm load (R) across the power supply, and you adjust the amps dial for 2A. The volts goes to 10V by itself (10V = 2A x 5 Ohms) and you see 2A on the amps meter.
Now you change the load to 10 Ohms, the volts go to 20V, and you still see 2A on the amps meter (20V = 2A x 10 Ohms).
Next you remove the load completely, now the volts goes to 30V, which is the max the PS can do, but the amps meter shows zero (no current is flowing).
Finally, you short out the power supply, the volts goes to a real small number (almost zero) and the amps meter shows 2A again. Why? because the short isn't zero Ohms, its very small, but not zero.

The power supply modifications you want to do aren't trivial. I'm an EE and I wouldn't do it, too much work. But if you want to read about it start looking at laboratory power supply circuits.