Charlie wrote:

Since I have these power supplies laying around, I can't resist asking.


A friend is going to buy and/or build a robotic CNC setup for his plama
torch.
A system is $5000 complete or a mainboard and software can be purchased
for $1500
or so with him supplying the motors, power supply, etc.

He says he needs 35 volt power supply with 35 amps.

So if I wire together 12 power supplys (12v, 9a), voila, 36 volts at 36
amps.

Hehe, it can't be that easy can it?

Nope.

If you put three twelve volt power supplies in series the most that you can
get out of them is the same as the lowest current rating of the three power
supplies.

If you had three 12 volt 35 amp power supplies then you could do the 35 amp
36 volt setup, if you isolated the power supplies from ground and made some
other modifications.

Try to find a dedicated power supply that is actually designed to the task
at hand.

Al Butler
ka0ies