On Sat, 26 May 2007 00:36:00 GMT, "Shaun Van Poecke"
wrote:

just some general questions here to try to get my head around DC motors....

is there a direct relationship between max RPM and torque for motors of the
same wattage? ie. if you have 2 ungeared motors that both draw 500watts and
one has a max 300RPM the other has a max 1000RPM, will the 300RPM motor have
more torque?

is maximum pull really available from zero RPM? many people say this, but
my experience with small DC motors (cordless drills etc) doesnt point at
this being true. Does the nature of the controller have an effect?

can all DC motors be wired up in reverse to go backwards?

Are they really a 'free voltage' device, can i use a 12VDC motor with 24VDC,
or a 36VDC motor with 48VDC? am i shortening the life of the motor by doing
so? some motors that i have seen specify operating voltage from say,
48-144VDC....

For two motors of the same given rating say, 500W, if i have a 24VDC and a
48V motor, will they actually have the same operating characteristics? Will
the 48V motor have more power than the 24V one, even though they consume the
same ammount of power? Does current draw remain the same as the voltage
goes up, or does it drop? Some manufacturers say that as the votage goes
up, so does the HP... ie. 8hp@48V, 12hp@60V etc etc....

is one sepcific type of design more efficient than any other?

To make a long story short, there are several different kinds of DC
motors, the two most common being series-wound and parallell wound.
The series-wound motor has the armature and field windings connected
in series with each other, and develops its highest torque at low RPMs
since that is when current draw and magnetic fields are the greatest.
Generally speaking, the rotational speed of a DC motor is proportional
to the voltage applied to it, and torque is proportional to the
current.

Wikipedia has a fairly lucid discussion of the details:

http://en.wikipedia.org/wiki/Electric_motor