Dc Generator Machines - Lincoln Electric CLASSIC III SVM 137-A Service Manual

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MECHANICAL
COUPLING

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 con-
nected to the shaft. Rotation of the armature through
the magnetic field produced by the stationary field
THEORY OF OPERATION
FIGURE E.4 – DC GENERATOR MACHINES
SHUNT FIELD WINDINGS
MAGNETIC FIELD
GENERATOR
ARMATURE
MAGNETIC FIELD
WINDINGS
SHUNT 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 rectified. In a
conventional DC Generator, rectification is provided
mechanically by means of a commutator. A commuta-
tor is a cylinder formed of copper segments insulated
from each other and mounted on, but insulated from,
the rotating shaft.
against the commutator surface connect the armature
windings to external terminals. The commutator pro-
vides full-wave rectification, transforming the voltage
waveform between brushes and making a DC voltage
available to the external circuit.
Classic III and IIID
C
U
F
R
I
R
E
E
L
N
D
T
DC CURRENT
BRUSH
ARMATURE
SHAFT
BRUSH
DC CURRENT
C
F
U
I
R
E
R
L
E
D
N
T
Stationary carbon brushes held
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