Figure 2-5.Compound-wound dc motor.
When the shunt field is connected in parallel with the series field and armature, it is called a "long
shunt" as shown in figure 2-5, (view A). Otherwise, it is called a "short shunt", as shown in figure 2-5,
TYPES OF ARMATURES
As with dc generators, dc motors can be constructed using one of two types of armatures. A brief
review of the Gramme-ring and drum-wound armatures is necessary to emphasize the similarities
between dc generators and dc motors.
The Gramme-ring armature is constructed by winding an insulated wire around a soft-iron ring (fig.
2-6). Eight equally spaced connections are made to the winding. Each of these is connected to a
commutator segment. The brushes touch only the top and bottom segments. There are two parallel paths
for current to follow one up the left side and one up the right side. These paths are completed through
the top brush back to the positive lead of the battery.
Figure 2-6.Gramme-ring armature.