What is "Analog Digital"?

Do you mean Analog Devices?

Hahahaha. Yeah, I meant Analog Devices. Derp.

Just how much chlorate were you intending to make?! >100A will need a significant amount of bulk graphite, or oxide or platinum coated electrodes, on top of everything else. A little 20A buck module will get you more than enough for a variety of experiments within days of operation, let alone weeks, say.

As far as my experience is concerned, I've designed and built a few projects, e.g. a nixie clock and a PDA-type device I use for work. Mostly digital stuff centered around MCUs, though. I'm happy to accept a challenge if there's a practicable solution unless I'm underestimating the complexity of the task.

@TimWilliams I do a lot of pyrotechnics and this is an effort to save some money on what I can make myself. Chlorates are cheap, perchlorates are a little pricier. I'm especially looking at trying to make my own ammonium perchlorate given the $20+/lb price tag on that material.

Then please do look into thermally observing your reactor. It's not likely, but you really don't want to rapidly oxidize any of your setup… and anything able to deliver 1200W into something that even remotely looks like a short might make it glow rather white. White glowing metallic conductor + APCP + Water = at least a stinky time.

@MarcusMüller I appreciate the advice. I've run a temperature and pH controlled bromate cell before at 35A for a few hundred hours. I enjoyed that a lot, which is why I'm interested in scaling up this time around.

OK great, "I am aware of how things can go south and I have some prior experience" is really what one wants to hear here, right. Why the 5V limit? Wouldn't it be more appropriate to limit the output current and work with whatever voltage that yields? I'm not familiar with the cells you need for this, but would rapidly pulsing the 12V on and off to keep the average current low enough suffice to keep the electrodes at working temperatures?

@MarcusMüller as long as your electrolyte solution is adequately saturated and your electrodes are correctly spaced, the potential needed to initiate the reaction is only in the ballpark of 3-5V and anything in excess of that just heats the cell, which can get problematic as you'll flash off chlorine. As to pulsing the current, I can't say that won't work, but in all my research I've never seen that attempted. I suspect it would be less effective than simply running lower rated supply.

@MarcusMüller AFAIK, applying high voltage transiently just wastes power in cell resistance, or if left on for long enough also violates current density ratings. (Or maybe always does; I'm not sure over what time period all the possible reactions occur.) Cell resistance is modest enough that CC, CV or a mix (resistive) is fine, just as long as it's adjustable to get nominal current density. (I ran a cell myself, many years ago; I still have a few pounds of product in storage that isn't even worth selling..)

@TimWilliams hm, then short of building a buck converter, the easiest solution would sound to be figuring out what the voltage feedback from the output side of these power supplies is, and modifying that so that the output voltage is lowered

That might work, say for three cells in series; but many PSU designs aren't quite that flexible. The other option is to shop around for a buck module, or enough that can be paralleled, or another device that can be (ab)used to this purpose (like a single-cell high-current Li-Ion charger, but without the charge controller, just the power stage); but these all involve some manner of either shopping for parts (against rules here) or design (how to wire up or rework something for purpose).

@FranklinKnight You are already in this hands, I think. Just a question about designed safety. Is the process for making this oxidizer carefully considered regarding safety? I have made various solid rocket fuels, some requiring melting prior to a pour into molds, and had to carefully design for safety. (Still have picric acid from that time.) I've not made ammonium perchlorate, though. So just checking.

@periblepsis yes, I've done my research on the appropriate and required safety measures for the task at hand. Perhaps of chief importance being eliminating residual chlorates after conversion to perchlorate before attempting synthesis of the ammonium perchlorate as ammonium chlorate is highly unstable. I sincerely appreciate the safety-minded sanity checks.

@TimWilliams I had considered series cells, but the MMO anodes are expensive and I've only got two currently (rated for 75A each). I could go with graphite, but that's a mess. Then I'd need to invest in more PtTi anodes for ClO4 conversion, too. For clarification, are you saying the buck converters can be paralleled to distribute the current load? If so, would that be likely to run into the issue of uneven load distribution as is the case for some regulators and ATX power supplies when ran in parallel? Pardon my ignorance on the finer points of SMPS functionality.

Hmmm. Having done more reading and considering the amount of current involved, would a multiphase converter be the most sensible and robust solution? Assuming it's within my ability to accomplish, of course.

Exactly and exactly: I would design (actually, I did, some years back; I have such a unit sitting on my Bench!) a current-mode multiphase converter, such that each channel (which might be modular for ~unlimited scalability) can be connected in parallel, and one master control system sets their current; thus enabling voltage or current regulation (or any combination). A fully standalone (CV) converter would have to be modified for parallel operation -- hence, some design effort required to integrate them.

@TimWilliams I'll start doing some deeper research on multiphase buck conversion so I can determine how feasible it'll be for me to design such a circuit. App notes are always interesting reads anyways. Hahaha. Given your experience with designing such a converter, is there some way for me to, and would you mind if I, reached out to you should I have a question(s) I can't find answers to elsewhere?

If you can't find answers, they may make good questions here, and I'll likely see them; or if you need something more conversational, you may find the EEVblog forum helpful.