Shaun Van Poecke wrote:
just some general questions here to try to get my head around DC motors....

snip

Most of your questions have been answered about as well as they can be
here. Places like the following are invaluable for the guy who is low
on the learning curve:

http://www.thelearningpit.com/

http://www.patchn.com/

http://www.ind-info.com/

There is a lot of fun and benefit to be taken from changing from single
speed to DC motors. Example, I have a 13" drill press in the garage and
it only offered a choice of five speeds from 500-3760 RPM. For bigger
drills and things like chamfering, 500 RPM is simply way too fast.
About 10 or 15 times too fast. And changing speeds on it requires a
minute or so (moving a belt on two step pulleys).

So I spend about $80 to buy a used DC motor (90V, Permanent Magnet type,
1/3HP, 1725 RPM) and a used DC motor controller on eBay. Figuring out
the wiring for the controller was mildly technical. Sort of a case of
deciphering some of the hieroglyphics on the terminal strip (I did not
get any docs with it and could not find the older model I bought on line).

But I asked the question he

http://www.plctalk.net/qanda/forumdisplay.php?f=2

and those folks sorted it right out for me.

So now I have a drill press that will run (and pull chips in steel) from
just barely turning (30 RPM or so) up to about 2,500 RPM and I never
have to mess with the belts for almost anything I would ever want to do.
I can get higher speeds by playing with the belt and step pulleys if I
want.

Playing with PLCs and inverters and controllers is a natural leap from
DC motors once you get started on making machines work better. My goal
has always been to do something better, I don't really understand a lot
of the theory and PLC programming and stuff but I can always fumble my
way through it and learn as I go.

But I can't think of very many of the metalworking and woodworking
machine I have ever owned that either were not better or would have been
better for having an single speed AC motor replaced with a DC motor and
a variable speed controller.

Your classic 10" table saw for woodworking for example, does *not*
really need a DC motor because the fixed blade diameter and tooth count
variable, along with enough HP and rigidity in the table, are the keys
to good work there. But planers or jointers can benefit from switch.

Now, if I want to add another switch to the controller, I can have
instantly adjustable spindle speeds *and* reversing too. That is
another thing that is much easier to do with DC motors.

Jack