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THEORY OF OPERATION
E-11 E-11
CLASSIC® 300D & 300G
DC GENERATOR MACHINES
The armature winding of a DC generator is located on
the rotating member. Current is conducted from it by
means of carbon brushes. The field winding is located
in the stator, which is stationary, and is excited by direct
current. The armature coil sides are placed at opposite
points on the rotating shaft with the conductors parallel
to the shaft. The armature assembly is normally turned
at a constant speed by a source of mechanical power
connected to the shaft. Rotation of the armature
through the magnetic field produced by the stationary
field winding induces a coil voltage in the armature
winding. The voltage induced in an individual armature
coil is an alternating (AC) voltage, which must be recti-
fied. In a conventional machine, rectification is provid-
ed mechanically by means of a commutator. A commu-
tator is a cylinder formed of copper segments insulated
from each other and mounted on, but insulated from,
the rotating shaft. Each copper segment is connected
to a corresponding armature winding. Stationary car-
bon brushes held against the commutator surface con-
nect the armature windings to external terminals. The
commutator provides full-wave rectification, transform-
ing the voltage waveform between brushes and mak-
ing available a DC voltage to the external circuit.
FIGURE E.10 - DC GENERATOR MACHINES
BRUSH
BRUSH
M
AGNETIC FIELD
GENERATOR
A
RMATURE
M
AGNETIC FIELD
S
HUNT FIELD WINDINGS
SHUNT FIELD WINDINGS
MECHANICAL
COUPLING
ARMATURE
S
HAFT
DC CURRENT
DC CURRENT
F
I
E
L
D
C
U
R
R
E
N
T
F
I
E
L
D
C
U
R
R
E
N
T
NOTE: Unshaded areas of Block Logic
Diagram are the subject of discussion
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