Why high current low voltage?

Question

The company I work for started a new contract building SCR controlled power supplies. They have a 480v input that's transformed down to 12.5/15/17.5 V. In testing we can push as much as 2800 A on the load side. To deal with the current we go so far as to build custom water cooled hoses with braided copper run through them. All I know about their application is that they heat ovens.

My question is why go through the trouble of building such complex power supplies with expensive water cooled conductors to heat an oven? Wouldn't high voltage with a resistive load achieve the same effect? My only guess so far is the safety on not working around high voltage.

Thoughts?

Answer 1

My guess is that it is an induction furnace. It doesn't heat the metal in the furnace (oven) by the heat dissipated in the water cooled copper coil, but instead the magnetic field created by the coil creates eddy currents in the metal in the furnace that needs to be heated. These currents in the metal cause heat dissipation in the metal, so they heat the metal from within. The bigger the amplitude of the current in the coil, the bigger the amplitude of the magnetic field strength created, the bigger the current induced in the metal to be heated, the more heat getting dissipated in the metal.

Answer 2

In a cable tray, the electrons don't care if you parallel ten 1000 kcmil aluminum wires or seven 1000 kcmil copper wires. However the person paying for the wire cares, so you use aluminum because it's 1/3 the price.

Different deal in a winding where you're all about making a lot of magnetic flux in a small space. There, density is so critical that you need copper.

Now why are they using water cooling on the windings? Transformers don't need that. You just make the copper thicker and it runs cooler, problem solved. You use the water cooling because it's in a furnace, and it's being punished by radiant heat from the items being heated up.

That all points to an induction furnace, as Cerike describes.