Alternative power supplies and voltages

[stupen]

I've been poking around power supplies for a while and have been seeing what I can get for amperages. A lot of higher torque DC motors pull a LOT of amps for 12V models (60A stall for the ones I've found new so far, but they also top out at over 20000rpm, too), and I think "low cost gearbox" is an oxymoron. I'm waiting on testing of the strength of RepRap'ed gears before final judgement on that, though. I've been looking for either higher voltage models or alternate power supplies. Also all the brushless DC motors I'm looking at for future use start at 24V and go up to 48V. This is a little of what I've found:

ATX Power Supply: the RepRap gold standard. A "good" one can actually be rated to 25A on the +12V supply. This can be as small as 350W and cost $30 new. Unfortunately, if you want to try and split phase it (+12 and -12 to get a 24V differential) you're only going to get an amp. Not Good. These also will not like you if you attempt to go beyond their rated capacities. They'll either fail or fold back and complain at 105% normally. Also may not like being paralleled on a case by case basis (harmonics, load balancing)

Industrial power supply: costs more, no 5V or 3.3V to leech off of for different models usually. Advantage, probably stabler, but still not recommended for brush motors at least (noise = instability = fault). I've been looking at a MeanWell 600W 24V supply (25A) to use for brushless motor power. This supply is carried by a few case mod sites for a lot less than industry, lowest price being about $140.

Transformer - rectifier - capacitor: toss in a soft start resistor/contactor and you're well on your way to making your own self-contained frequency drive. I've seen a surplus 12V 10A transformer for $10 at my local surplus store. It was even an isolation transformer. This should mean that I can, carefully, parallel the inputs and outputs to generate higher amp blocks. I can series the outputs to generate 12, 24, 36, and 48V. With a slow blow or circuit breaker, they can also surge several times their rated current for short periods. Disadvantages: lower efficiency power wise, not regulated so I have to watch my overvoltage trips (although this might be easy enough to fix). Plus I need to remember what DC voltage I get when I recitfy and cap-smooth a 12VAC signal.

I believe that all current RepRaps run off of 12V in one way or another, mostly computer PSU's. Does anyone else use something different on a regular basis? My personal power interests all all over the board (due to different motor requirements). I know I've seen interest once or twice (probably Zach) in moving Mendel along a brushless DC servo system, but I doubt that will be feasible if 12V stays the standard.



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