thanks for explaining that a little better, I was listening and get what your saying now, but i still have a lot to learn when it comes to motors and inductance. I can understand the armature would have less inductance because it's constantly rotating, and the different segments of the coil are being energized, and when the motor stalls, the windings on that particular segment on the armature overheats and fries because that segment of coil between the commutator segments can't handle that much energy transference.
So with this motor, i'm dealing with a fixed number of 6 commutator segments. So basically it's the armature's winding inductance that controls the overall power output for a motor? A lower inductance on the armature translates to higher current through the field coils? Am i getting that right?
The power output is determined by the load - more mechanical load (ie torque), and the armature slows down,
so less back-EMF from the motion is present, so the current increases (which will generate more torque
to balance out with the load). The difference between supply voltage and back-EMF is whats left to drive
current through the armature winding's inductance and resistance. Normally that will be a small fraction
of the supply voltage as only back EMF represents useful mechanical work.
With a universal motor like this running off AC the details are complicated as the voltages are changing
all the time, as is the magnetic field from the stator, and there are various phase shifts going on, so the paragraph
above is really an oversimplification, but your intuition about the armature inductance isn't quite there
Field coils use their inductance to limit current, armature windings need less inductance as the back-EMF does
most of this job. In fact you want the armature inductance a lot less as current is being switched
from segment-to-segment by the commutator rapidly and the current must change rapidly enough or
the motor's top speed will be limited. Universal motors can spin at 15,000rpm or so, the armature
segments see higher rotational frequencies than the mains frequency.
In both cases you want the resistance of the windings to be low to reduce wasted power in the windings.
Ultimately the heat in the windings will limit the continuous power rating of most motors. Universal motors
tend to be shunt-wound, so the field coils are independent of the armature current. The stall current
in the armature is set by the mains impedance of the winding (at stall there is no commutation, so the
effective frequency is that of the mains). It may be either resistance or inductance that dominate for
the armature winding at stall. At high speed the armature inductance will be dominant and be a limiting
factor for the speed (along with the supply voltage).
In designing a motor the interaction between winding resistance, inductance and mass has to be taken
into account. Its quite a balancing act, and commercial motors will have everything pretty much optimized
for efficiency, cost, temperary overload handling and max temperature rise.
Something like a Dremel will probably be on its 2nd or 3rd iteration of detailed motor design too - its likely
to be closely tailored to the specific needs of the tool.