MULTIQUIP DCA Series Service And Troubleshooting Manual page 11

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