MULTIQUIP DCA Series - Page 11

GENERATOR SERVICE AND TROUBLESHOOTING MANUAL — REV. #0 (08/29/23) — PAGE 11
Stationary Exciter Field
The stationary exciter eld (Ex Fg) Figure 3 receives
DC current from the automatic voltage regulator (AVR)
to create an electromagnetic field that produces the
magnetic ux required to induce an AC voltage into the
rotating exciter armature. The strength of the magnetic
eld is controlled by the amount of DC current received
from the AVR.
Figure 3. Stationary Exciter Field
Exciter Armature
The exciter armature (Ex Ar) Figure 4 is a three-phase
armature and it rotates inside the exciter eld and cuts
through the magnetic lines of ux created by the exciter eld
which through magnetic induction induces an AC voltage
into the exciter armature windings.
The magnitude of the induced voltage is controlled by
the strength of the exciter’s magnetic eld and how fast
the exciter armature cuts through the lines of ux (Engine
speed).
Figure 4. Exciter Armature
GENERATOR THEORY
Rectiers (Re)
Rectiers (Figure 5) are mounted on the end of the rotor
plate. The rectiers vary between models, as exampl the
DCA45-70 utilize three single-phase half wave rectiers.
DCA125-150 utilize two full wave three-phase rectiers
connected in parallel.
The rectiers receive three-phase AC voltage from the
exciter armature and converts the AC to DC voltage which
is sent to the main eld to create a rotating electromagnetic
eld.
Figure 5. Rectiers
CONVERTS AC TO DC
RECTIFIER
DCA 6-70
DA7
GENERATORS
HALF-WAVE
RECTIFIER
RECTIFIER
DCA 125-600
GENERATORS
FULL-WAVE
RECTIFIER