On 15 Jun 2005 11:36:20 -0700, "Too_Many_Tools"
wrote:

Thanks for the reply.

I would agree that cordless tools have a spot in the AHP workshop since
one can recharge them during off load hours.

Where would one find 12v motors in the suitable HP and speeds to
retrofit something like a table saw?

In considering this subject, a lineshaft approach does come to mind but
unfortunately you rarely see the needed equipment at HD or Lowes. I am
not to crazy about chucking all the stationary power tools that have
taken me decades to collect. Also, lineshafts take up room, linedriven
tools are required to stay in one place and cannot be mounted on wheels
to optimize shop space as needed. A workshop should be no larger than
necessary for the heating/cooling aspect that also takes energy.

TMT

I really hesitate to jump in on this topic, but I advise you to make
sure to do your research carefully before pursuing the replacement of
AC motors with DC motors.

In the early days of homepower which was nearly universally 12V on the
primary side, this was a pretty common practice, but in the overall
picture of things today I'm not sure it's warranted in the general
case.

At one time I was given to understand that DC motors are just innately
more efficient than AC. It appears that this is not necessarily so,
and has much to do with the crappy design and build quality of
"shovelware" AC motors than any basic electromechanical principles. To
know whether you would actually be further ahead after a DC
conversion, you would have to consider each case individually.
Ignoring power factor, a 12V load of power "x" draws 10 times the
current that an 120VAC load will draw. Will the losses you avoid by
bypassing the inverter get chewed up in the wire? How close to the
battery room will the workshop be?

I started out at 12V primary by virtue of buying a house with an
existing PV system. Like many frontier homebrew systems, it had
started as a purely DC system to which an inverter was added later.

Having no plumbing in the house, I've acquired a number of small 12V
pumps for various specific purposes, such as our bucket shower.
Fortunately this hasn't represented a significant investment. With
each system upgrade I left myself options for going to a higher
primary voltage, and recently made the move to 24V when we replaced
our chargerless mod square wave inverter with a sine wave
inverter/charger. At some distant point in the future we might even
make the jump to 48V, but for the moment, 24V was "just right."

The punchline is that our little pumps (and other 12V DC loads) are
now running off a 24V/12V DC-DC converter. In the overall picture of
things this crazy scenario actually still makes sense here, but again
these are *small* loads.

The moral is that when you choose to run DC loads, you're creating
specialized equipment and there are serious implications that might
not be immediately obvious. If you stick with AC loads, your wire runs
can be far longer for a given power throughput / wire guage, you can
reconfigure the primary side of your system without affecting anything
on the load side, use a common AC generator when it's more convenient
or more sensible to do so, or take your gear with you and use it
elsewhere.

Having "inherited" a mixed DC/AC system and lived with it, off-grid,
for five years, there is no question in my mind that the new house we
build here will be wired almost entirely for conventional AC and will
likely have only some emergency lighting (power room!), and perhaps a
few very special-purpose devices and outlets wired for DC.

YMMV.

-=s