ARMY TM 9-6115-671-14
AIR FORCE TO 35C2-3-446-32
MARINE CORPS TM 09249A/09246A-14A
1-30
1.16.12
Generator Assembly.
1.16.12.1
General. Revolving field type generators have a DC field revolving within a stationary AC winding
called the stator. See brushless generator schematic, Figure 1-28. AC power is distributed from the
generator through leads connected to the stator windings. There are no sliding contacts between the
AC winding and the load, therefore, great amounts of power may be drawn from this generator.
To energize the field, DC excitation must be applied to the generator field coils. The excitation current
is supplied from a brushless exciter mounted on the generator shaft.
The brushless exciter is actually an AC generator with its output rectified through a full wave bridge
circuit. This type of brushless exciter will provide the necessary excitation current. The generator set
field flash circuit, activated during each engine start, applies voltage to the exciter stator to begin the
voltage build-up process to energize the generator field.
The generator output voltage is controlled by controlling the alternating field current. This is
accomplished by regulating the exciter field coil voltage. The exciter field coil voltage is regulated
with a solid state type automatic voltage regulator.
1.16.12.2
Damper Bars. Damper bars are inserted through the field laminations and welded at the end to a solid
copper plate. The damper windings provide stable parallel operation, reduce damping current losses,
and limit the increase of third harmonic voltage with increase in load.
1.16.12.3
Brushless Exciter. The brushless exciter consists of an armature with a three-phase AC winding and
rotating rectifier assembly within a stationary field.
The stationary exciter field assembly is mounted in the main generator frame. The exciter armature is
press fit and keyed onto the shaft assembly. The rotating rectifier assembly slides over the bearing end
of the generator rotor shaft and is secured with bolts and washers to an adapter hub which is shrunk on
the generator shaft.
1.16.12.4
Rotating Rectifier Bridge. The rotating rectifier bridge consists of rectifying diodes mounted on a
brass heat sink which is in turn mounted on an insulating ring. The entire assembly bolts to the adapter
on the generator shaft. Therefore, the rotating rectifier assembly will rotate with the exciter armature
eliminating the need for any sliding contacts between the exciter output and the alternator field.
1.16.12.5
Exciter Field. The exciter field on the high frequency exciter consists of laminated segments of high
carbon steel which are fitted together to make up the field poles. The field coils are placed into the
slots of the field poles.
1.16.12.6
Exciter Field Coil Voltage Source. Field coil DC voltage is obtained by rectifying the voltage from a
phase to neutral line of the generator output, or other appropriate terminal, to provide the needed
voltage reference.
The rectifier bridge is an integral part of the static regulator. The static regulator senses a change in the
generator output and automatically regulates current flow in the exciter field coil circuit to increase or
decrease the exciter field strength. An external adjust rheostat sized to be compatible with the regulator
is used to provide adjustment to the regulator sensing circuit.
1.16.12.7
Balance. The rotor assembly is precision balanced to a high degree of static and dynamic balance.
Balance is achieved with the balance lugs on the field pole tips. The balance will remain dynamically
stable at speed in excess of the design frequencies.
