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Producto: ENGINE - MACHINE

Modelo: 3412 ENGINE - MACHINE 38S
Configuración: 3412 INDUSTRIAL ENGINE 38S00001-13235

Operación de Sistemas
2301 ELECTRIC GOVERNOR FOR GENERATOR SET AND INDUSTRIAL ENGI
Número de medio -SENR2928-01 Fecha de publicación -01/04/1985 Fecha de actualización -02/06/2016

SENR29280001

Systems Operation

2301 Electric Governor System

The 2301 Electric Governor Control System consists of the components that follow: 2301 Electric
Governor Control (EGC), Actuator, Magnetic Pickup, and an optional Preregulator.

The 2301 Electric Governor System gives precision engine speed control. The 2301 Control measures
engine speed constantly and makes necessary corrections to the engine fuel setting through an
actuator connected to the fuel system.

The engine speed is felt by a magnetic pickup. This pickup makes an AC voltage that is sent to the
2301 Control. The 2301 Control now sends a DC voltage signal to the actuator.

The actuator changes the electrical input from the 2301 Control to a mechanical output that is
connected to the fuel system by linkage. For example, if the engine speed is more than the speed
setting, the 2301 Control will decrease its output and the actuator will now move the linkage to
decrease the fuel to the engine.

2301 LOAD SHARE CONTROL (Parallel Unit)

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2301 STANDBY CONTROL (Nonparallel Unit)

MAGNETIC PICKUP LOCATION ON EARLIER 3500 ENGINE

1. Magnetic pickup.

MAGNETIC PICKUP LOCATION ON LATER 3500 ENGINE

1. Plug (one of three available locations on top of flywheel housing).

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ACTUATOR LOCATION ON 3500 ENGINE

2. EG-10PC Actuator.

BASIC 2301 LOAD SHARING SYSTEM

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BASIC 2301 STANDBY SYSTEM

Magnetic Pickup

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SCHEMATIC OF MAGNETIC PICKUP

The magnetic pickup is a single pole, permanent magnet generator made of wire coils around a
permanent magnet pole piece. As the teeth of the flywheel ring gear go through the magnetic lines of
force around the pickup, an AC voltage is made. The ratio between the frequency at this voltage and
the speed of the engine is directly proportional.

This engine speed frequency signal (AC) is sent to the 2301 Control Box where a conversion is made
to DC voltage. The DC signal is now sent on to control the actuator, and this voltage is inversely
proportional to engine speed. This means that if engine speed increases, the voltage output to the
actuator decreases. When engine speed decreases, the voltage output to the actuator increases.

2301 Nonparallel (Standby) Control Box

The Rated and Low Idle engine speed are set with speed setting potentiometers. An optional remote
Speed Trim potentiometer will give approximately ± 6% speed setting adjustment.

The Gain and Stability Potentiometers control the response of the engine to a change in load.
Increased gain is used to get a faster response time. The Stability Potentiometer is used to get the best
speed stability for the gain setting that is used.

A capacitor can be used between terminals T15 and T16 to control the amount of time it takes the
engine to go from Low Idle to Rated Speed.

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WIRING DIAGRAM FOR 2301 NONPARALLEL CONTROL BOX (8N408)

A Droop Potentiometer can be connected between terminals T13, T14 and T15 to control the amount
of speed droop. Droop is necessary when paralleling with a utility bus, or a unit with a hydra-
mechanical governor.

An oil pressure switch is connected between terminals T9 and T10. This switch will not permit the
control box to accelerate the engine to Rated speed if there is not enough engine oil pressure at low
idle. The switch is normally open, and when closed by constant oil pressure, it does not affect the
system until the engine is started again. However, if the oil pressure drops below the switch setting,
the control box will return the engine to Low Idle.

The speed failsafe circuit will return the voltage output of the control box to zero if the magnetic
pickup signal has a failure. This will cause the actuator to move to the FUEL OFF position. Also, the
engine will not start if the magnetic pickup signal has a failure.

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NOTE: On the 7N182 Control Box, the jumper between terminals T3 and T4 must be removed to
deactivate the speed failsafe circuit for test purposes. On the 8N408 Control Box, a jumper must be
added between terminals T3 and T4 to deactivate the failsafe circuit for test purposes.

2301 STANDBY CONTROL SCHEMATIC

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2301 NONPARALLEL CONTROL BOX (8N408)

2301 Parallel (Load Sharing) Control Box

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2301 PARALLEL CONTROL BOX

The 2301 Parallel Control Box has two functions: precision engine speed control and kilowatt load
sharing. The system measures engine speed constantly, and makes necessary corrections to the engine
fuel setting through an actuator connected to the fuel system.

The engine speed is felt by a magnetic pickup. As the teeth of the flywheel ring gear go through the
magnetic lines of force around the pickup, an AC voltage is made. The ratio between the frequency of
this voltage and the speed of the engine is directly proportional. An electric circuit inside the control
box feels this AC voltage. In response it sends a DC voltage from the control, inversely proportional
to engine speed, to the actuator.

The actuator is connected to the fuel system by linkage. It changes the electrical input from the
control box to mechanical output that changes the engine fuel setting. For example, if the engine
speed was more than the speed setting, the control box will decrease fuel to the engine.

Kilowatt load sharing between a group of engine driven generator sets is made possible by electric
circuits in the control box. The load on each generator in the system is measured constantly by its
control box. Loads are compared between control boxes through paralleling wires between all the
units on the same bus. From the input of the paralleling wires, the load sharing circuits in the control
box make constant corrections to the voltage sent to the actuators. This gives kilowatt load sharing.

The Rated and Low Idle engine speeds are set with speed setting potentiometers. An optional remote
Speed Trim Potentiometer will give ± 4% speed setting adjustment. The Ramp Time Potentiometer
controls the amount of time it takes the engine to go from Low Idle to Rated Speed. An oil pressure
switch is connected between terminals T14 and T15, and this switch is normally open. When the

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engine oil pressure increases to the switch high pressure setting, the switch closes. This permits the
control box to now automatically accelerate to Rated speed. If the oil pressure decreases to the switch
low pressure setting, the switch will open and the control box will now automatically return the
engine to Low Idle.

A minimum fuel switch can be connected between terminals T22 and T23. This gives an optional
method for shutdown (make reference to Service Procedure H).

The Gain and Stability Potentiometers control the response of the engine to a change in load. The
Gain Potentiometer is used to decrease response time to a minimum. The Stability Potentiometer is
used to get the best speed stability for the gain setting that is used.

The Speed Droop Potentiometer controls the amount of speed droop. It can be set between 0 and 13%.
Droop is necessary when paralleling with a utility bus, or a unit with a hydra-mechanical governor.

NOTE: Potential transformers and current transformers must be connected for speed droop to
function.

The De-Droop Potentiometer gives compensation (during isochronous operation) for droop caused by
component tolerances and outside electrical noise. Make this adjustment after equipment installation
is complete.

The Load Gain Potentiometer is set so that the ratio between the actual kilowatt output and the rated
kilowatt output of each unit in the system is the same.

The speed failsafe circuit will stop all voltage output to the actuator if the magnetic pickup signal has
a failure. This will cause the actuator to move to the FUEL OFF position. Also, the engine will not
start if the magnetic pickup signal has a failure.

On the 8N409 Control Box terminals T12 and T13 are used for either 24V or 32V DC. Even though
all the units are connected in parallel, terminals T25 of each unit must be connected together in series.
This gives a high voltage selection of all battery voltages. Selection of the high voltage as the
common supply to all units prevents small speed changes caused by different battery supply voltages.

NOTE: See Service Procedure F to find which of the Control units have the high voltage selection
feature.

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WIRING DIAGRAM FOR 2301 PARALLEL CONTROL BOX (8N409)

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2301 LOAD SHARING CONTROL SCHEMATIC

Preregulator Box Assembly

The optional 4W5391 Preregulator Box Assembly is a protective component that mounts directly to
the 2301 Control Box and limits the amount of supply voltage to the control. The preregulator also
uses a 0.75A fuse for current protection from lead shorts.

This preregulator is designed to give protection to 2301 Governor Controls from possible damage by
any of the problems that follow:

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1. Battery Disconnect During Operation - engine driven alternators and battery chargers
produce damaging positive battery lead voltages (spikes up to 150 volts) if the battery becomes
disconnected during operation. The 2301 Control can be permanently damaged if battery lead
voltage exceeds 40 volts. The preregulator protects against voltage spikes by limiting supply
voltage to 36 ± 2 volts.
2. Nicad Battery Systems - charging rates on 32 volt Nicad battery systems can exceed 40 volts.
The preregulator will reduce charging rates of up to 70 volts to a safe level of 36 ± 2 volts.

4W5391 PREREGULATOR BOX ASSEMBLY

3. Reverse Voltage Damage - incorrect wiring at installation can cause reverse polarity voltage
to the supply circuit, and the result will be permanent damage to the 2301 Control. The
preregulator also gives protection against these reverse voltages.
4. Lead Shorts - incorrect wiring at installation or lead insulation damage during use can also
cause lead shorts. The preregulator is fused to prevent any current surges that can result in
damage to 2301 Control.

For installation and correct wiring procedures, see Service Procedure V.

PREREGULATOR INSTALLED ON 2301 LOAD SHARING CONTROL BOX

Relay Assembly (For Cold Start)

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Cold starting an engine below certain temperatures can reduce the voltage available to the 2301 Load
Sharing (Parallel) units. This condition will not permit full fuel linkage travel. The 9G8187 Relay
Assembly makes sure that the control units now receive the necessary voltage.

9G8187 RELAY ASSEMBLY

It is recommended that the cold start relay be installed on 2301 Control units if the engine is to be
started at temperatures below:

Control units without 4W5391 Preregulator: 4°C (40°F)

Control units with 4W5391 Preregulator installed: 10°C (50°F)

NOTE: The cold start relay cannot be used for tandem engine applications since these applications
require a separate power supply for the 2301 Control unit.

For installation wiring diagram, see Service Procedure W.

EG-10PC Actuator

ACTUATOR
1. EG-10PC Actuator.

The EG-10PC Actuator is an engine driven device that hydraulically changes an electrical input to a
mechanical output (terminal shaft rotation) that controls the engine fuel rack.

This actuator is used with the 2301 Electric Governor Control Box. The 2301 Control sends a voltage
input signal to the solenoid coils of the actuator. The position of the actuator terminal (output) shaft is

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directly proportional to this input signal to the actuator. When the voltage signal to the actuator is
stopped, the terminal shaft of the actuator will move to a position to shut the fuel off to the engine.

The direction of rotation for the correct oil flow is determined at the factory by placement of plugs in
specific oil passages in the actuator base and case. There is a relief valve in the actuator to maintain
operating oil pressure at approximately 2750 kPa (400 psi) above the supply oil pressure.

NOTE: The only adjustment that can be made to the EG-10PC Actuator is the external needle valve.
See subject Needle Valve.

To better understand the complete operation of the actuator, a separate explanation of each system
follows. These systems are: Oil Pump, Mechanical, Electrical, Hydraulic and Feedback (Mechanical
& Hydraulic Buffer).

SCHEMATIC OF EG-10PC ACTUATOR

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Oil Pump System

Engine lubrication oil is supplied (from the engine sump) through inside passages to the suction sides
of the three gear actuator oil pump. The pump gears push the oil to the pressure side of the pump to
fill the system and increase the hydraulic pressure. When the pressure becomes great enough to
overcome the force of the relief valve spring, the relief valve plunger is pushed down to uncover the
bypass opening. This bypass oil now goes back to the inlet side of the pump.

3500 Series Engines use fuel linkages of higher effort (more resistance to movement) than previous
Caterpillar engines. The EG-10PC Actuator is used to provide greater driving characteristics than the
EG-3P Actuators commonly used on other engines. The EG-10PC Actuator has the ability to drive the
fuel linkage during hot engine restarts when both of the main problems (thin oil and increased linkage
effort) are present to make a high effort actuator necessary.

Basic Mechanical System

The power piston is connected to the actuator terminal (output) shaft. The engine fuel rack linkage is
also connected to the terminal shaft. When there is an increase or decrease in engine load, the
movement of the power piston will turn the terminal shaft. The linkage will now move the fuel racks
to the new fuel setting to maintain the correct engine speed at the new load condition.

Basic Electrical System

A magnetic pickup is installed in the flywheel housing of most engines (in the cover of the front gear
train on earlier 3500 Series engines) to make an AC voltage signal. The frequency of this AC signal is
controlled by the speed of the gear teeth that pass through the magnetic field of the pickup. This
engine speed frequency signal is sent to the 2301 Electric Governor Control. The 2301 Control has a
speed sensor that now makes a comparison between this input signal for actual engine speed and the
desired engine speed that the control box has been set to maintain. If the actual engine speed and the
speed setting are not the same, the 2301 Control will send a corrected DC voltage signal to the
solenoid coils of the actuator. The actuator will now adjust to a new fuel setting to make the engine
speed the same as the speed setting.

The pilot valve plunger is connected to a permanent magnet that is spring-suspended in the field of a
two-coil solenoid. The output signal from the 2301 Control is applied to the solenoid coils to make a
magnetic force which is proportional to the current in the coils. This force always tries to move the
magnet and pilot valve plunger in the down (increase fuel) direction. The centering spring (at top of
plunger) force always tries to move the magnet and pilot valve plunger in the up (decrease fuel)
direction.

When the unit runs on-speed at steady-state conditions, these two forces are equal but in opposite
directions. The pilot valve plunger at this time will be "centered" (the control land covers the control
port).

If there is a decrease in the engine speed setting at the 2301 Control, or an increase in engine speed
(because of a decrease in the engine load), the input voltage to the actuator solenoid coils will be
decreased. The magnetic force of the solenoid coils also will now be decreased. Since the force of the
centering spring is now greater than the force of the coils, the pilot valve plunger will move above the

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"centered" position. This allows oil under the power piston to drain to sump, and the down movement
of the power piston will cause rotation of terminal shaft in the decrease fuel direction.

If there is an increase in the engine speed setting at the 2301 Control, or a decrease in engine speed
(because of an increase in engine load), the input voltage to the actuator solenoid coils will be
increased. The magnetic force of the solenoid coils also will now be increased. Now the force of the
coils will be greater than the force of the centering spring, and the pilot valve plunger will move down
to allow pressure oil under the power piston.

Since the surface area (that oil pressure works against) of the power piston is larger at the bottom than
at the top, the piston will move up. The rotation of the terminal shaft will now be in the increase fuel
direction.

Basic Hydraulic System

The power piston is the part of the actuator that does all of the work. Under normal conditions, the oil
pressures at both the top and bottom of the piston are balanced, and the piston remains stationary at
the "centered" position. The pilot valve plunger controls the flow of oil to and from the power piston.
The control land at the bottom of the pilot valve plunger is just large enough to completely cover the
control port in the pilot valve bushing when the plunger is exactly "centered."

If the signal from the 2301 Control makes the pilot valve plunger move up, the oil under the power
piston can drain past the control land to sump. The higher oil pressure at the top of the piston will now
move the piston down until the control land of the plunger will again close the control port. This
piston movement will also move the terminal shaft (in the decrease fuel direction), since they are
connected together.

If the signal from the 2301 Control makes the pilot valve plunger (and control land) move down,
pump oil pressure can now pass through the control port to the bottom of the piston. Even though the
pump oil pressure in the circuit above the piston is the same as the circuit below the piston, the piston
will move up. This is due to a larger surface area available to the oil pressure at the bottom of the
piston than the surface area at the top of the piston. The movement of the piston will now turn the
terminal shaft in the increase fuel direction.

Feedback Systems

A high degree of stability is necessary to maintain a constant output from the generator set. The
stability of a system controlled by the 2301 Control is increased with the use of a temporary actuator
feedback signal that biases (makes a correction to) the 2301 Control command signal to the pilot
valve plunger. Since the 2301 Control makes an adjustment rapidly to a change in engine load, the
actuator can make the engine go into a "hunt" condition (temporary increase and decrease in engine
speed) if the corrections are too sensitive. The purpose of the feedback system is to prevent over-
correction to the load change.

The EG-10PC Actuator is different because two feedback systems are used, one mechanical and one
hydraulic. Under normal conditions, the mechanical system will correctly control the actuator.
However, during cold engine start-up conditions, the addition of the hydraulic buffer system
eliminates erratic (variable) speed problems caused by the cold engine oil. The result of the two

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systems is constant speed control at all times. The explanation for the operation of each feedback
system is as follows:

Mechanical Feedback System

The temporary feedback signal is accomplished in this system by the addition of linkage and a
restoring spring arrangement that applies a secondary force to the centering spring.

Decreased Engine Load

With this condition, the voltage signal to the solenoid coils is decreased and the centering spring force
will raise the pilot valve plunger to release oil under power piston to sump. The power piston will
now move down to turn terminal shaft in the decrease fuel direction. The mechanical linkage of the
feedback lever is also connected to the terminal shaft and will move down. The restoring lever will
also move down to put the restoring spring in compression. The restoring spring force is opposite the
upward force of the centering spring. The resultant force (from the restoring lever and restoring
spring) will now help the solenoid move the pilot valve plunger back down to the "centered" position
before it would have been moved down by just the voltage signal change to the solenoid itself.
Therefore, the actuator acts to position the terminal shaft in the new decreased fuel position without
allowing an underspeed condition.

Increased Engine Load

This condition will increase the voltage signal to the solenoid coils, and the pilot valve plunger will
move down because the magnetic force is greater than the centering spring force. The control land
will now let pressure oil to the bottom of the power piston, and the power piston will move up. The
terminal shaft will turn in the increase fuel direction and, at the same time, move the feedback lever
and the restoring lever up. Now there is less compression on the restoring spring.

The resultant centering spring force (upward) is now stronger than the magnetic force of the solenoid
coils, and the pilot valve plunger will move up to the "centered" position before it would have been
moved up by just the voltage signal change to the solenoid itself. Therefore, the actuator has moved
the terminal shaft in the increased fuel position without allowing an overspeed condition.

Hydraulic Buffer Feedback System

The temporary feedback signal in this sytem uses a pressure differential that is applied across the
compensation land of the pilot valve plunger. This pressure differential is accomplished by the buffer
system.

Decreased Engine Load

With the pilot valve "centered," no oil flows to or from the power piston. If there is a decrease in load
(causing an increase in engine speed), the solenoid coils will get a voltage signal to lift the pilot valve
plunger. The oil under the power piston will now be released to go to sump. Pump pressure oil on the
right side of the buffer piston will now force the buffer piston to the left. This displacement of oil in
the power cylinder oil pressure circuit will move the power piston down and cause rotation of the
terminal shaft in the decrease fuel direction.

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The movement of the buffer piston to the left also decreases the compression of the buffer spring on
the right side, and increases the compression of the buffer spring on the left side. The increase of the
left buffer spring force (caused by resistance to this movement) results in a small decrease in oil
pressure on the left side of the buffer piston and on the bottom surface of the pilot valve plunger
compensation land. This pressure difference on the two sides of the compensation land makes a force
(greater at the top) to push the pilot valve plunger back down to the "centered" position.

When the terminal shaft has turned far enough to satisfy the new fuel requirement, the force of the
pressure difference on the compensation land will have again "centered" the pilot valve plunger (even
though the engine speed is not yet completely back to normal). The movement of the power piston,
and the terminal shaft, is now stopped.

The continued decrease of engine speed to its steady-state setting results in a continued increase in
downward force to the pilot valve plunger as the 2301 Control signal (to the solenoid coils) increases
to its on-speed value. At the same time, the pressure difference on each side of the buffer piston (and
at top and bottom of the compensation land) is being released by the flow of oil through the needle
valve orifice. This controlled discharge allows the buffer piston to return slowly to its normal,
"centered" position. The increase in the solenoid voltage signal to its on-speed value, and the
controlled reduction of the pressure difference on the two sides of the compensation land occur
exactly at the same rate (while the pilot valve plunger remains "centered") until the engine is again at
the on-speed condition at the decreased load.

Increased Engine Load

When the engine load is increased, engine speed will decrease. The 2301 Control will now send a
stronger signal (more voltage) to the solenoid coils, and the pilot valve plunger will move down. The
control land has now opened the control port to allow pump pressure oil to the bottom of the power
piston. Even though the pressure on each side of the power piston is approximately the same at this
time, the pressure against the larger surface area at the bottom of the piston makes a larger force and
the power piston will move up. This upward piston movement will cause terminal shaft rotation in the
increase fuel direction, and the engine speed will begin to increase.

When the power piston moves up, the displacement of the oil above the power piston will move the
buffer piston to the right. This movement will cause a pressure increase on the bottom surface of the
compensation land. The pilot valve plunger will now move up to close the control port of the pilot
valve bushing before engine speed returns to normal. Any movement of the power piston, and the
terminal shaft, is now stopped.

As the engine starts its return to normal speed, the controlled discharge of the oil pressure difference
through the needle valve orifice is at the same rate that the voltage signal is decreased to the solenoid
coils. The engine now returns to its steady-state condition, with the terminal shaft already set at the
new fuel position that is required for the increase in engine load.

Needle Valve

The needle valve orifice is adjustable to permit a variable time rate that a pressure differential acts on
the compensation land of the pilot valve plunger. This permits limited control of the EG-10PC
actuator to be calibrated (set) to the response characteristics of the engine. Normally the settings can
be made in the range of 3/4 to 2 turns open to get the desired characteristics.

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EG-3P Actuator

ACTUATOR

The EG-3P Actuator is also used with the 2301 Control Systems. The actuator's terminal (output)
shaft position is directly proportional to the input signal to the actuator. The actuator normally goes to
minimum fuel position if the electric signal is stopped.

The output signal of the 2301 electric control is a level of voltage that determines the actuator
terminal shaft position required to maintain a particular load on the engine. The voltage is always the
same polarity. This type of control unit requires an actuator in which the output shaft takes a position
proportional to the voltage of the input signal.

The main element of the actuator is an electrohydraulic transformer which controls oil flow to and
from the power piston through the action of a polarized solenoid. The position of the actuator shaft is
proportional to the input current to the solenoid coil controlling the hydraulic pilot valve plunger.

Operation of the actuator is as follows:

The drive shaft rotates between 1200 and 3000 rpm. It can rotate in one direction only. The direction
of rotation is determined by the placement of plugs in the oil passages in the actuator base and case. A
relief valve is incorporated within the actuator to maintain the operating oil pressure at approximately
2400 kPa (350 psi) above supply pressure.

Engine lubrication oil from an internal sump in the engine enters the suction side of the oil pump. The
pump gears carry the oil to the pressure side of the pump, first to fill the oil passages and then to
increase the hydraulic pressure. When the pressure becomes great enough to overcome the relief valve
spring force and push the relief valve plunger down to uncover the bypass hole, the oil goes back
through the inlet side of the pump.

The movement of two opposing pistons turns the actuator terminal shaft. The engine fuel linkage is
fastened to the terminal shaft. Pressure oil from the pump is supplied directly to the bottom of the
loading piston. Pressure in this hydraulic circuit always moves the terminal shaft in the "decrease
fuel" direction.

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Since the linkage that connects the loading piston to the terminal shaft is shorter than the linkage that
connects power piston to the terminal shaft, the loading piston cannot move up unless the power
piston moves down. The power piston moves down only when the oil blocked under it can go to
sump.

The flow of oil to and from the power piston is controlled by the pilot valve plunger. With the pilot
valve plunger "centered," no oil flows to or from the power piston. The pilot valve plunger is
"centered" when its control land exactly covers the control port in the pilot valve bushing.

The greater of two forces moves the pilot valve plunger up or down. When the forces are equal, the
plunger does not move.

The pilot valve plunger is connected to a permanent magnet that is spring-suspended in the field of a
two-coil solenoid. The output signal from the electric control box is directed to the solenoid coils and
produces a force, proportional to current in the coils, which moves the magnet - and pilot valve
plunger - down.

A spring force moves the pilot valve plunger and magnet up. The centering spring is positioned on top
of the case in which the solenoid coils are located. It puts a constant upward force on the pilot valve
plunger. The restoring spring puts a downward force on the pilot valve plunger. The downward force
from the restoring spring depends upon the position of the restoring lever. The restoring lever moves
up to decrease the restoring spring force as the terminal shaft turns in the "increase fuel" direction.
The resultant force from the combined output of the centering spring and restoring spring is a force
that moves the pilot valve plunger in the "up" direction. This combined force increases as the terminal
shaft moves in the "increase fuel" direction.

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SCHEMATIC OF EG-3P ACTUATOR (WITHOUT NEEDLE VALVE ADJUSTMENT)

With the unit running on-speed under steady-state conditions, the combined spring force and the force
from the solenoid coils are equal but opposite.

When the unit is running on-speed under steady-state conditions, the pilot valve plunger is "centered".
A decrease in voltage input to the solenoid coils (due to a decrease in speed setting or a decrease in
load) decreases the force and will lower the pilot valve plunger. However, the unchanged spring force
is now greater and lifts the plunger above center. As oil moves from under the power piston, the
terminal shaft turns in the "decrease fuel" direction. When the terminal shaft has turned far enough for
the new fuel requirement, the increase in restoring spring force will equal the decrease in downward
force from the solenoid coils, and the pilot valve plunger will be "centered" again by equal but
opposite forces that push on it.

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When the voltage signal input to the solenoid coils increases (due to an increase in load or an increase
in speed setting), similar but opposite conditions will take place. The now greater downward force
from the solenoid coils will move the pilot valve plunger down. The power piston and restoring lever
will be moved up, decreasing the downward force of the restoring spring. When the terminal shaft
turns far enough for the new fuel requirement, the decrease in restoring spring force now equals the
increase in downward force from the solenoid coils, and the pilot valve plunger will be centered again
by the equal but opposite forces that push on it.

Copyright 1993 - 2024 Caterpillar Inc. Mon Apr 15 07:13:36 EST 2024
Todos los derechos reservados.
Red privada para licenciados del SIS.

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