(constant speed) or droop (speed regulation) operation
decrease in speed taking place when the governor output
for prime movers such as diesel or gas engines and steam
shaft moves from the minimum to the maximum
or gas turbines.
position in response to a load increase. It is expressed
as a percentage of rated speed. Speed droop is provided
Isochronous operation provides constant engine
in the EGB-2P through linkage, which varies the loading
speed for single unit operation or when several units are
on the speeder spring as a function of the power piston
paralleled on an isolated bus. Droop operation allows
position. The change in speeder spring force for a given
paralleling of two or more units and provides speed
movement of the power piston is determined by the
regulation as a function of generator load.
position of the adjustable pin in the linkage between the
Two engines driving a common load can be
power piston and speeder spring. If the pin is on the
operated from one 2301 electric control by connecting
same centerline as the speed droop lever pivot arm, there
the actuators in series. Since each actuator receives the
is no change in speeder spring force as the power piston
same input signal, each engine receives the same
moves. The governor then operates as an isochronous
amount of fuel.
(constant speed) control. The further the adjustable pin
is moved away from the pivot arm centerline, the greater
The output of the 2301 electric control provides a
the change in compression of the speeder spring for a
unidirectional continuous voltage level to the actuator,
given power piston movement.
which provides the desired speed and load relationship
With the unit operating under the electric control,
called for by the input signals to the control panel. This
type of output signal requires a proportional actuator.
the speed droop feature is, in effect, inoperative. During
The proportional actuator contains a servo piston, which
such operation, the governor power piston remains in
operates in proportion to the input voltage applied
the maximum position for all engine or turbine loads
(except possibly momentarily during transients).
The electric control also contains a ramp generator
Therefore, the speed droop linkage does not alter the
module which controls the rate of acceleration during
speeder spring compression when the actuator is
initial start-up. After the unit reaches set speed further
controlling.
control action from the ramp generator is blocked.
The load sensor provides either parallel isochronous
MAINTENANCE
load sharing or droop operation for the unit.
As stated earlier, the source of most troubles in any
As with any governor, the engine should be
hydraulic actuator or governor stems from dirty oil.
equipped with a separate overspeed device. This
Valves, pistons, and plungers will stick and even freeze
prevents runaway (loss of control with maximum rpm)
in their bores, due to excessive wear caused by grit and
if a failure should render the governor inoperative.
impurities in the oil. If this is the case, erratic operation
and poor response can be corrected by flushing the unit
OPERATION
with fuel oil or kerosene. The use of commercial
solvents is not recommended as they may damage seals
The 2301 system is programmed to maintain preset
or gaskets.
speed- and load-sensing levels. These are in proportion
If the speed variation of the unit is erratic but small,
to the capacity of the unit being controlled. For
excessive backlash or a tight meshing of the gears
purposes of explanation, the system is divided into two
driving the unit may be the cause. If the speed variation
sections: input and control (see fig. 9-15).
is erratic and large and cannot be corrected by
adjustments, repair or replace the unit.
Input Section
The input section consists of the following
2301 ELECTRIC GOVERNOR
components:
The 2301 electric control (fig. 9-14) is a
1. Load sensor,
combination of four modules mounted on a single
control panel. The control panel is the controlling
2. External magnetic pickup, and
portion of the 2301 system. The system is comprised of
3. Speed sensor.
the 2301 electric control (described here), a magnetic
pickup, current and potential transformers, and a
These circuits detect and process the speed and load
input signals.
hydraulic actuator. The system can provide isochronous
9-21
