Product Manual

Direct Current (DC)
Another commonly used motor in industrial applications is the direct
current motor. It is often used in applications where adjustable speed
control is required.
Permanent magnet DC designs are generally used for motors that
produce less than 5 HP. Larger horsepower applications use shunt-
wound direct current motors.
Both designs have linear speed/torque characteristics over the entire
speed range. SCR rated motors – those designed for use with common
solid-state speed controls – feature high starting torque for heavy
load applications and reversing capabilities, and complementary active
material to compensate for the additional heating caused by the
rectified AC input. Designs are also available for use on generated low-
voltage DC power or remote applications requiring battery power.
Gearmotors
A gearmotor is made up of an electric
motor, either DC or AC, combined with
a geared speed reducer. Spur, helical
or worm gears may be used in single
or multiple stages. The configuration
may be either that of a parallel shaft,
emerging from the front of the motor,
or a right-angle shaft. Gearmotors
are often rated in input horsepower;
however, output torque, commonly
measured in inch-pounds, and output
speed are the critical values.
-19-
DC motors can be operated
from rectified alternating
current of from low-voltage
battery or generator source.
This is a low-voltage design,
which includes external con-
nection lugs for the input
power. With the rear end-
shield removed, as in this
view, the brush assemblies
and commutator that form a
DC motor’s electrical heart
are clearly visible.
Speed reduction
gearing is visible in this cutaway
view of a parallel-shaft gearmotor.
Shown is a small, sub-fractional
horsepower gearmotor.