in response to the control signal. This shaft
OPERATING MODES
controls the engine's LFV through a mechanical
linkage. If the engine speed increases to a preset
The governor system of both the model 104
limit because of a failure in the electronic control,
and the model 139 have two basic operating
then the centrifugal governor section of the
modes, NORMAL (isochronous) and DROOP.
actuator will automatically assume control of the
output shaft. Engine speed will then be controlled
Isochronous Mode
at a point slightly above the normal operating
speed.
This mode provides constant speed operation,
regardless of load. When generators are operated
Motor-Operated Potentiometer
in parallel and in the isochronous mode, the
governor system maintains a constant speed. It
The operating point of the governor is set by
also controls the load division between paralleled
the motor-operated potentiometer. The individual
generators. The isochronous mode is selected
frequency adjust controls at the EPCC or the
when the EPCC selector or the SWBD selector
SWBD are used to adjust the potentiometer.
is in the NORMAL position. The load sharing
These controls adjust the position of the motor-
function is automatically enabled when a
operated potentiometer to a higher or lower
generator operating in the NORMAL mode is
position. If generators are operated in parallel
paralleled with another generator.
controls enabled, the motor-operated potenti-
Droop Mode
ometer returns to a calibrated 60-Hz position. You
can make adjustments by using the SYSTEM
In this mode, the governor system still
FREQUENCY ADJUST control at the EPCC.
regulates engine speed, but the speed will decrease
This control will position a master frequency
slightly with an increase in load. Sometimes the
trimmer in the EPCC. It sends equal adjust signals
generator is paralleled with a constant frequency
bus (such as shore power) while in the droop
directly to each generator's ECU. The frequency
of the bus can be changed without disturbing the
mode. In this case, the governor cannot control
load balance between operating units. During
speed since it is held constant by the bus
automatic paralleling operations, the APD will
frequency. Instead, it will control the load carried
adjust the oncoming generator for synchroniza-
by the generator. In this way, the droop mode
tion. This adjust signal is also a direct input into
provides load control of a generator paralleled
the ECU. It is in effect only during automatic
with shore power. It also can unload a generator
paralleled with another GTGS without disturbing
paralleling conditioning. Figure 3-24 is a governor
interface diagram.
system frequency. When the selector is in the
DROOP position, droop mode is selected at the
Electronic Control Unit
EPCC or the SWBD.
The ECU of the Woodward 2301 governor
MODEL 104 GOVERNOR SYSTEM
system is modular in design. It is composed of
the motor-operated potentiometer, the master
The engine speed governor on the model 104
frequency trimmer, the APD, an amplifier, the
GTGS is the Woodward 2301 electrohydraulic
fuel control actuator, two power supplies, an
control system. It has a backup centrifugal
accessory box, two filters, and a load sensor. The
governor override. Three major components
following paragraphs describe the function of
w i t h i n the system are a motor-operated
these subunits and are keyed to figure 3-25, a
potentiometer, an ECU, and an EG actuator. The
functional diagram of the Woodward 2301
motor-operated potentiometer is located at the
ECU. The ECU is mounted in the GCU. The
governor.
The motor-operated potentiometer (1) supplies
primary function of the GCU is to provide
a reference to the amplifier. When the electric
generator field excitation and voltage control in
plant operates in the manual, manual permissive,
either the automatic or manual mode. The GCU
or droop mode, frequency adjust commands will
is a solid-state electronic package. It processes
cause the motor to rotate in the raise or lower
input commands and feedback signals to generate
direction. This changes the reference corre-
a signal to position the engine-mounted EG
spondingly. When operating in the automatic
actuator. The actuator positions its output shaft
3-32