Introduction

NOTE: For Specifications with illustrations, make reference to SPECIFICATIONS for 3406B INDUSTRIAL & MARINE ENGINE ATTACHMENTS, Form No. SENR4024. If the Specifications in Form SENR4024 are not the same as in the Systems Operation and the Testing and Adjusting, look at the printing date on the back cover of each book. Use the Specifications given in the book with the latest date.

Woodward PSG Governors

SCHEMATIC OF PSG GOVERNOR
1. Return spring. 2. Output shaft. 3. Output shaft lever. 4. Strut assembly. 5. Speeder spring. 6. Power piston. 7. Flyweights. 8. Needle valve. 9. Thrust bearing. 10. Pilot valve compensating land. 11. Buffer piston. 12. Pilot valve. 13. Pilot valve bushing. 14. Control ports. A. Chamber. B. Chamber.

Introduction

The Woodward PSG (Pressure Compensated Simple Governor) can operate as an isochronous or a speed droop type governor. It uses engine lubrication oil, increased to a pressure of 1200 kPa (175 psi) by a gear type pump inside the governor, to give hydramechanical speed control.

Pilot Valve Operation

The fuel injection pump camshaft drives a governor drive unit. This unit turns pilot valve bushing (13) clockwise as seen from the drive unit end of the governor. The pilot valve bushing is connected to a spring driven ballhead. Flyweights (7) are fastened to the ballhead by pivot pins. The centrifugal force caused by the rotation of the pilot valve bushing causes the flyweights to pivot out. This action of the flyweights changes the centrifugal force to axial force against speeder spring (5). There is a thrust bearing (9) between the toes of the flyweights and the seat for the speeder spring. Pilot valve (12) is fastened to the seat for the speeder spring. Movement of the pilot valve is controlled by the action of the flyweights against the force of the speeder spring.

The engine is at the governed (desired) rpm when the axial force of the flyweights is the same as the force of compression in the speeder spring. The flyweights will be in the position shown. Control ports (14) will be closed by the pilot valve.

Fuel Increase

When the force of compression in the speeder spring increases (operator increases desired rpm) or the axial force of the flyweights decreases (load on the engine increases) the pilot valve will move in the direction of the drive unit. This opens control ports direction of the drive unit. This opens control ports (14). Pressure oil flows through a passage in the base to chamber (B). The increased pressure in chamber (B) causes power piston (6) to move. The power piston pushes strut assembly (4), that is connected to output shaft lever (3). The action of the output shaft lever causes counterclockwise rotation of output shaft (2). This moves fuel control linkage (15) in the FUEL ON direction.

As the power piston moves in the direction of return spring (1) the volume of chamber (A) increases. The pressure in chamber (A) decreases. This pulls the oil from the chamber inside the power piston, above buffer piston (11) into chamber (A). As the oil moves out from above buffer piston (11) to fill chamber (A) the buffer piston moves up in the bore of the power piston. Chamber (A and B) are connected respectively to the chambers above and below the pilot valve compensating land (10). The pressure difference felt by the pilot valve compensating land adds to the axial force of the flyweights to move the pilot valve up and close the control ports. When the flow of pressure oil to chamber (B) stops so does the movement of the fuel control linkage.

PSG GOVERNOR INSTALLED
2. Output shaft. 15. Fuel control linkage.

Fuel Decrease

When the force of compression in the speeder spring decreases (operator decreases desired rpm) or the axial force of the flyweights increases (load on the engine decreases) the pilot valve will move in the direction of speeder spring (5). This opens control ports (14). Oil from chamber (B) and pressure oil from the pump will dump through the end of the pilot valve bushing. The decreased pressure in chamber (B) will let the power piston move in the direction of the drive unit. Return spring (1) pushes against strut assembly (4). This moves output shaft lever (3). The action of the output shaft lever causes clockwise rotation of output shaft (2). This moves fuel control linkage (15) in the FUEL OFF direction.

EARLIER PSG GOVERNOR
6. Power piston. 8. Needle valve. 10. Pilot valve compensating land. 11. Buffer piston. 14. Control ports. A. Chamber. B. Chamber.

As power piston (6) moves in the direction of the drive unit the volume of chamber (A) decreases. This pushes the oil in chamber (A) into the chamber above buffer piston (11). As the oil from chamber (A) flows into the power piston, it moves the buffer piston down in the bore of the power piston. The pressure at chamber (A) is more than the pressure at chamber (B). Chambers (A and B) are connected respectively to chambers above and below the pilot valve compensating land (10). The pressure difference felt by the pilot valve compensating land adds to the force of the speeder spring to move the pilot valve down and close the control ports. When the flow of oil from chamber (B) stops so does the movement of the fuel control linkage.

Hunting

There is a moment between the time the fuel control linkage stops its movement and the time the engine actually stops its increase or decrease of rpm. During this moment there is a change in two forces on the pilot valve, the pressure difference at the pilot valve compensating land and the axial force of the flyweights.

The axial force of the flyweights changes until the engine stops its increase or decrease of rpm. The pressure difference at the pilot valve compensating land changes until the buffer piston returns to its original position. A needle valve (8) in a passage between space (A) and (B) controls the rate at which the pressure difference changes. The pressure difference makes compensation for the axial force of the flyweights until the engine stops its increase or decrease of rpm. If the force on the pilot valve compensating land plus the axial force of the flyweights is not equal to the force of the speeder spring, the pilot valve will move. This movement is known as hunting (movement of the pilot valve that is not the result of a change in load or desired rpm of the engine).

PSG GOVERNOR INSTALLED
8. Needle valve.

The governor will hunt each time the engine actually stops its increase or decrease of rpm at any other rpm than that desired. The governor will hunt more after a rapid or large change of load or desired rpm than after a gradual or small change.

Speed Adjustment

Later PSG governors use a clutch assembly (2) driven by a 110V AC/DC or 24V DC reversible synchronizing motor (1) to move link assembly (3) up or down. The clutch assembly protects the motor if the adjustment is run against the stops. The motor is controlled by a switch that is remotely mounted. The clutch assembly can be turned manually if necessary.

PSG GOVERNOR
1. Synchronizing motor. 2. Clutch assembly. 3. Link assembly.

Speed Droop

(Earlier PSG Governor)

Speed droop is the difference between no load rpm and full load rpm. This difference in rpm divided by the full load rpm and multiplied by 100 is the percent of speed droop.

The speed droop of the PSG governor can be adjusted by movement of an adjustment lever on the outside of the governor that is connected to pivot pin (2) by link (4). The governor is isochronous when it is adjusted so that the no load and full load rpm is the same. Speed droop permits load division between two or more engines that drive generators connected in parallel or generators connected to a single shaft.

EARLIER PSG GOVERNOR
1. Bracket. 2. Pivot pin. 3. Output shafts.

EARLIER PSG GOVERNOR
2. Pivot pin. 4. Link.

Speed droop adjustment on PSG governors is made by movement of pivot pin (2). When the pivot pin is put in alignment with the output shafts, movement of the output shaft lever will not change the force of the speeder spring. When the force of the speeder spring is kept constant the desired rpm will be kept constant. See PILOT VALVE OPERATION. When the pivot pin is moved out of alignment with the output shafts, movement of the output shaft lever will change the force of the speeder spring proportional to the load on the engine. When the force of the speeder spring is changed the desired rpm of the engine will change.

Speed Droop

(Later PSG Governor)

Speed droop is the difference between no load rpm and full load rpm. This difference in rpm divided by the full load rpm and multiplied by 100 is the percent of speed droop.

The speed droop of the PSG governor can be adjusted. The governor is isochronous when it is adjusted so that the no load and full load rpm is the same. Speed droop permits load division between two or more engines that drive generators connected in parallel or generators connected to a single shaft.

LATER PSG GOVERNOR
1. Pivot pin. 2. Bracket for droop adjustment screw. 3. Output shafts.

Speed droop adjustment on PSG governors is made by movement of pivot pin (1). When the pivot pin is put in alignment with the output shafts, movement of the output shaft lever will not change the force of the speeder spring. When the force of the speeder spring is kept constant, the desired rpm will be kept constant. See PILOT VALVE OPERATION. When the pivot pin is moved out of alignment with the output shafts, movement of the output shaft lever will change the force of the speeder spring proportional to the load on the engine. When the force of the speeder spring is changed, the desired rpm of the engine will change.

An adjustment lever outside the governor connected to pivot pin (1) by link (4) is used to make an adjustment of the speed droop.

LATER PSG GOVERNOR
1. Pivot pin. 4. Link.

Wiring Diagrams

Many types of electrical systems are available for these engines. Some charging systems use an alternator and a regulator in the wiring circuit. Others have the regulator inside the alternator.

A fuel or oil pressure switch is used in all systems with an external regulator. The switch prevents current discharge (field excitation) to alternator from the battery when the engine is not in operation. In systems where the regulator is part of the alternator, the transistor circuit prevents current discharge to the alternator and the fuel or oil pressure switch is not required.

All wiring schematics are usable with 12, 24, 30 or 32 volts unless the title gives a specific description.

NOTE: Wire and cable shown dotted on wiring diagrams is to be supplied by customer. The chart that follows gives the correct wire sizes and color codes. The abbreviations given below are used with the wiring diagrams in this section.

AS

AIR SHUTOFF SOLENOID

BATT

BATTERY

C

COMMON TERMINAL

CB

CIRCUIT BREAKER - AMPS

CT

CRANK TERMINATE

DC

DIRECT CURRENT

DSS

DUAL SPEED SWITCH

EG

GOVERNOR ACTUATOR

ENG FW

ENGINE FLYWHEEL

GSM

GOVERNOR SYNCHRONIZER MOTOR

MPU

MAGNETIC PICKUP

MS

MAGNETIC SWITCH

NC

NORMALLY CLOSED

NEG

NEGATIVE

NO

NORMALLY OPEN

OPS

OIL PRESSURE SWITCH

OSS

OVERSPEED SWITCH

POS

POSITIVE

PS

PINION SOLENOID

RESS

REMOTE EMERGENCY SHUTDOWN SWITCH

RNS

REMOTE NORMAL SHUTDOWN SWITCH

RS

RACK SHUTOFF SOLENOID

SHLD

CABLE SHIELD

SIG

SIGNAL FROM MAGNETIC PICKUP

SM

STARTER MOTOR

SR

SHUTDOWN RELAY

SS

SHUTOFF SOLENOID

TD

TIME DELAY RELAY

TS

TERMINAL STRIP

V

VOLTAGE

VDC

VOLTAGE DIRECT CURRENT

VTS

VOLTAGE TRANSIENT SUPPRESSOR

WTS

WATER TEMPERATURE SWITCH

Grounded Electrical Systems

These systems are used in applications when it is not necessary to prevent radio distortion and/or chemical changes (electrolysis) of grounded components.

(Regulator Inside Alternator)

CHARGING SYSTEM
1. Ammeter. 2. Alternator. 3. Battery.

CHARGING SYSTEM WITH ELECTRIC STARTER MOTOR
1. Start switch. 2. Ammeter. 3. Alternator. 4. Battery. 5. Starter motor.

Insulated Electrical Systems

These systems are most often used in applications where radio interference is not desired or where conditions are such that grounded components will have corrosion from chemical change (electrolysis).

(Regulator Inside Alternator)

CHARGING SYSTEM
1. Ammeter. 2. Alternator. 3. Battery.

CHARGING SYSTEM WITH ELECTRIC STARTER MOTOR
1. Start switch. 2. Ammeter. 3. Alternator. 4. Battery. 5. Starter motor.

Grounded Electrical Systems (Cont.) (Regulator Separate From Alternator)

CHARGING SYSTEM
1. Ammeter. 2. Regulator. 3. Pressure switch (N.O.). 4. Resistor (used with 30 and 32V systems). 5. Battery. 6. Alternator.

CHARGING SYSTEM WITH ELECTRIC STARTER MOTOR
1. Start switch. 2. Ammeter. 3. Regulator. 4. Resistor (for 30 and 32V systems). 5. Battery. 6. Starter motor. 7. Pressure switch (N.O.). 8. Alternator.

Insulated Electrical Systems (Cont.) (Regulator Separate From Alternator)

CHARGING SYSTEM
1. Ammeter. 2. Regulator. 3. Pressure switch (N.O.). 4. Resistor (used with 30 and 32V systems). 5. Battery. 6. Alternator.

CHARGING SYSTEM WITH ELECTRIC STARTER MOTOR
1. Start switch. 2. Ammeter. 3. Regulator. 4. Resistor (for 30 and 32V systems). 5. Battery. 6. Starter motor. 7. Pressure switch (N.O.). 8. Alternator.

Grounded Electrical Systems (Cont.)

The following diagrams are for use only when an alternator or charging generator is not used in the engine electrical system.

SYSTEM WITH ONE STARTER MOTOR
1. Start switch. 2. Starter motor. 3. Battery.

Insulated Electrical Systems (Cont.)

The following diagrams are for use only when an alternator or charging generator is not used in the engine electrical system.

SYSTEM WITH ONE STARTER MOTOR
1. Start switch. 2. Starter motor. 3. Battery.

Electric Tachometer Wiring

1. Magnetic pickup.

2. Terminal Connections - terminals 18 and 19 on load sharing governor control and terminals 7 and 8 on standby governor control.

3. Tachometer.

4. Ground connection - governor control chassis ground.

5. Governor control terminal strip.

6. Wiring connections - for second tachometer circuit if needed.

7. All wire must be 22AWG shielded cable or larger.

8. Dual speed switch terminal strip.

9. Ground connection - ground to engine.

Automatic Start/Stop System - (Non-Package Generator Sets)

AUTOMATIC START/STOP SYSTEM SCHEMATIC (Hydraulic Governor)
1. Starter motor and solenoid. 2. Shutoff solenoid. 3. Fuel pressure switch. 4. Water temperature switch. 5. Oil pressure switch. 6. Overspeed contactor. 7. Battery. 8. Low lubricating oil pressure light (OPL). 9. Overcrank light (OCL). 10. Overspeed light (OSL). 11. High water temperature light (WTL). 12. Automatic control switch (ACS).

An automatic start/stop system is used when a standby electric set has to give power to a system if the normal (commercial) power supply has a failure. There are three main sections in the system. They are: the automatic transfer switch, the start/stop control panel (part of switch gear) and the electric set.

Automatic Transfer Switch

The automatic transfer switch normally connects the 3-phase normal (commercial) power supply to the load. When the commercial power supply has a failure the switch will transfer the load to the standby electric set. The transfer switch will not transfer the load from commercial to emergency power until the emergency power gets to the rated voltage and frequency. The reason for this is, the solenoid that causes the transfer of power operates on the voltage from the standby electric set. When the normal power returns to the rated voltage and frequency and the time delay (if so equipped) is over, the transfer switch will return the load to the normal power supply.

AUTOMATIC TRANSFER SWITCH (ATS)

1. E1, E2 and E3 input to ATS from emergency source.

2. N1, N2 and N3 input to ATS from normal source.

3. T1, T2 and T3 output from ATS to the load.

4. Transfer mechanism.

AUTOMATIC START/STOP SYSTEM SCHEMATIC (2301 Control System)
1. Magnetic pickup. 2. Starter motor and solenoid. 4. Oil pressure switch 1 (OPS1). 5. Water temperature switch. 7. Overspeed switch. 8. Battery. 9. Low lubricating oil pressure light (OPL). 10. Overcrank light (OCL). 11. Overspeed light (OSL). 12. High water temperature light (WTL). 13. Automatic control switch (ACS). 14. EG-3P Actuator. 15. 2301 Control Box. 16. Oil pressure switch 2 (OPS2).

Control Panel

The main function of the control panel is to control the start and shutoff of the engine.

AUTOMATIC START/STOP CONTROL PANEL
1. Overcrank light (OCL). 2. Low lubricating oil pressure light (OPL). 3. Overspeed light (OSL). 4. Automatic control switch (ACS). 5. High water temperature light (WTL).

The engine control on the automatic start/stop control panel is an automatic control switch (ACS) with four positions. The positions of switch (4) are: OFF/RESET, AUTO, MAN and STOP. Each light (1), (2), (3) and (5) goes ON only when a not normal condition in the engine stops the engine. The light for the condition in the engine that stopped the engine is ON even after the engine has stopped. Switch (4) must be moved to the OFF/RESET position for the light to go OFF. Each light will go ON, for a light test, when the light is pushed in and held in.

When the generator is to be used as a standby electric power unit, the automatic control switch is put in the AUTO position. Now, if the normal (commercial) electric power stops, the engine starts and the generator takes the electric load automatically. When the normal (commercial) electric power is ON again, for the electric load, the circuit breaker for the generator electric power automatically opens and the generator goes off the electric load. After the circuit breaker for the generator opens, the engine automatically stops.

When the automatic control switch (ACS) is moved to the MAN position, the engine starts. It is now necessary for the circuit breaker for the generator electric power to be closed manually. If the generator is a standby electric power unit and the automatic control switch (ACS) is in the MAN position when normal (commercial) electric power is ON again, the generator circuit breaker opens and the engine stops automatically the same as when the switch (ACS) is in the AUTO position.

The engine will stop with the automatic control switch (ACS) in either the AUTO or MAN positions if there is a not normal condition in the engine. The not normal condition in the engine that can stop the engine is either low lubricating oil pressure, high engine coolant (water) temperature or engine overspeed (too much rpm). When any of these conditions stops the engine, the light for the not normal condition will stay ON after the engine is stopped. The fourth not normal condition light is ON only when the starter motor runs the amount of seconds for the overcrank timer (engine does not start).

Move the automatic control switch (ACS) to the OFF/RESET position and the not normal condition lights go OFF.

Electric Set

The components of the electric set are: the engine, the generator, the starter motor, the battery, the shutoff solenoid and signal switches on the engine. The electric set gives emergency power to drive the load.

An explanation of each of the signal components is given in separate topics.

Wiring Diagrams

The following wiring diagrams are complete to show the connections of the automatic start/stop components with the engine terminal strip (TS1). The diagrams show all available options for both the hydraulic governor application and the 2301 Control System application.

For a more complete explanation of operation of the automatic start/stop system, refer to Floor Standing Switchgear Form No. SENR7970.

Automatic Start/Stop Wiring

A

DC AMMETER

ACS

ENGINE CONTROL SWITCH

ALT

CHARGING ALTERNATOR

AR

ARMING RELAY

ARX

AUXILIARY RELAY

ASO

AIR SHUTOFF SOLENOID

OCT

OVERCRANK TIMER

CB

CIRCUIT BREAKER

CCM

CYCLE CRANKING MODULE

CCT

CYCLE CRANK RELAY

CDT

COOL DOWN TIMER

CDTR

COOL DOWN TIMER RELAY

CRC

CYCLE CRANK LOGIC TIMER

CTS

CRANK TERMINATE SWITCH

DSS

DUAL SPEED SWITCH (INCLUDES CTS AND OSS)

GS

GOVERNOR SWITCH

GSM

GOVERNOR SYNCHRONIZING MOTOR

I

INITIATE CONTACT (REMOTE START)

MS

MAGNETIC SWITCH (CRANK CIRCUIT)

OCR

OVERCRANK RELAY

OP

OIL PRESSURE GAUGE SENDER

OPG

OIL PRESSURE GAUGE

OPR

LOW OIL PRESSURE RELAY

OPS

OIL PRESSURE SWITCH

OPT

OPTIONAL EQUIPMENT

OSR

OVERSPEED RELAY (IN DSS)

OSS

OVERSPEED SWITCH (IN DSS)

PIL

PANEL ILLUMINATION LAMP

PLS

PANEL LAMP SWITCH

PS

PINION SOLENOID

RR

RUN RELAY

SS

SHUTOFF SOLENOID

SM

STARTER MOTOR

TDR

TIME DELAY RELAY

TDX

TIME DELAY AUXILIARY RELAY

WT

WATER TEMPERATURE GAUGE SENDER

WTG

WATER TEMPERATURE GAUGE

WTR

HIGH WATER TEMPERATURE RELAY

WTS

WATER TEMPERATURE SWITCH

*

INDICATES EQUIPMENT EXTERNAL TO CONTROL PANEL

o

TERMINAL STRIP POINT (CONTROL PANEL)

[ ]

TERMINAL STRIP POINT (GENERATOR TERMINAL BOX)

[]

RELAY CONTACT LINE NUMBER

NOTE A: Terminals 13 and 14 of the generator box will be connected to terminals 13 and 14 of the control panel when the CDT is not supplied.

NOTE B: Red jumper wire from terminal strip point number 4A to 4 in control panel must be removed when the cycle cranking module (CCM) is used.

NOTE C: Auxiliary relay (ARX) contacts are to be customer wired. See Relay Contact Schematic.

NOTE D: Dotted lines shown on Control Panel Wiring Schematic show engine wiring.

NOTE E: The overcrank timer (OCT) is to be adjusted to the 30 second setpoint (red dot). When cycle cranking (CCM) is used, the overcrank timer (OCT) is to be adjusted to the 90 second setpoint (white dot).

NOTE F: ACS switch contacts shown with switch in auto position.

NOTE G: Jumper wire from terminal 72 to terminal 73 must be removed when DC ammeter (A) is used.

NOTE H: Jumper wire from terminal 13 to terminal 133 to be removed if additional fault shutdowns are added. Examples: reverse power relay or remote shutdown. Insert a normally closed switch between terminal 13 and terminal 133.

CONTROL PANEL WIRING SCHEMATIC

Automatic Start/Stop Wiring For Non-Package Generator Set (Used With Hydramechanical or Woodward PSG Governors)

For wire sizes and color codes see the chart at the front of Wiring Diagrams section.

Wires and cables shown in dotted lines are customer supplied wiring.

STARTING SYSTEM WITH ONE STARTER MOTOR
1. Magnetic switch. 2. Circuit breaker. 3. Starter motor. 4. Battery. 5. Circuit breaker. 6. Terminal strip (on engine).

DUAL SPEED SWITCH
7. Magnetic pickup. 8. Dual speed switch. 9. Time delay relay. 10. Oil pressure switch. 11. Governor synchronizing motor. 12. Water temperature switch.

SHUTOFF SOLENOIDS
13. Circuit breaker. 14. Rack shutoff solenoid. 15. Circuit breaker. 16. Air shutoff solenoids. 17. Diode.

AUTOMATIC START/STOP SYSTEM SCHEMATIC

Automatic Start/Stop Wiring For Non-Package Generator Set (Used With Woodward 2301 Governor)

For wire sizes and color codes see the chart at the front of Wiring Diagrams section.

Wires and cable shown in dotted lines are customer supplied wiring.

STARTING SYSTEM WITH ONE STARTER MOTOR
1. Magnetic switch. 2. Circuit breaker. 3. Starter motor. 4. Battery. 5. Circuit breaker. 6. Terminal strip.

SYSTEM COMPONENTS
7. Oil pressure contactor. 8. Dual speed switch. 9. Governor actuator. 10. Time delay relay. 11. Magnetic pickup. 12. Oil pressure switch. 13. Water temperature switch.

NOTE A: For standby operation - magnetic pickup (MP) and oil pressure contactor (OPS) must be wired to governor control with two conductor shielded cable (Beldon Mfg. Co. type 8780 or equivalent). (MP) should be connected to terminals 7 and 8 on governor control assembly and (OPS) should be connected to terminals 9 and 10 on governor control assembly. Shields should be grounded at governor control grounding stud. Individual shields should not have multiple ground connections. Magnetic pickup from governor control assembly is not needed. Use magnetic pickup from speed switch group. Wire from magnetic pickup to (DSS). Then wire from (DSS) to governor control assembly using two conductor shielded cable - terminal 4 on (DSS) to terminal 8 on governor control assembly, terminal 3 on (DSS) to terminal 7 on governor control assembly. Remove (MP) shield from terminal 2 on DSS and connect to shield on governor cable, ground the shield at the governor control assembly ground stud. The (DSS) may be installed physically near the governor control assembly if desired.

NOTE B: For load sharing operation - magnetic pickup (MP) and oil pressure contactor (OPS) must be wired to governor control with two conductor shielded cable (Beldon Mfg. Co. type 8780 or equivalent). (MP) should be connected to terminals 18 and 19 on governor control assembly and (OPS) should be connected to terminals 14 and 15 on governor control assembly. Shields should be grounded at governor control assembly grounding stud. Individual shields should not have multiple ground connections. Magnetic pickup (MP) from governor control assembly is not needed. Use (MP) from speed switch group. Wire from (MP) to (DSS). Then wire from (DSS) to governor control assembly using two conductor shielded cable - terminal 4 on (DSS) to terminal 19 on governor control assembly, terminal 3 on (DSS) to terminal 18 on governor control assembly. Remove (MP) shield from terminal 2 (DSS) and connect to shield on governor cable. Ground the shield at the governor control assembly grounding stud. The (DSS) may be installed physically near the governor control assembly if desired.

AUTOMATIC START/STOP SYSTEM SCHEMATIC

Electric Shutoff And Alarm Systems

Introduction

There are three types of electrical protection systems available for the 3406B Engines.

1. Water Temperature and Oil Pressure Protection.

2. Water Temperature, Oil Pressure and Overspeed Protection.

3. Automatic Start Stop Systems for Non-Package Generator Sets.

The electric shut-off system is designed to give protection to the engine if there is a problem or a failure in any of the different engine systems. The engine systems that are monitored are: engine overspeed, starter motor crank terminate, engine oil pressure and engine coolant temperature.

The electric protection system consists of the electronic speed switch and time delay relay. This system monitors the engine from starting through rated speed.

Dual Speed Switch (DSS) - The speed switch has controls (in a single unit) to monitor engine overspeed and crank terminate speed.

Engine Overspeed - An adjustable engine speed setting (normally 118% of rated speed) that gives protection to the engine from damage if the engine runs too fast. This condition will cause a switch to close that shuts off the fuel to the engine.

Crank Terminate (Starter Motor) - An adjustable engine speed setting that gives protection to the starter motor from damage by overspeed. This condition will cause a switch to open that stops current flow to starter motor circuit, and the starter motor pinion gear will then disengage from engine flywheel ring gear. The crank terminate can also be used to activate the time delay relay.

Time Delay Relay - This relay has special ON/OFF switches with two controls that will either make the relay activate immediately, or after a 9 second delay. The time delay relay is used to arm the shutdown system. The time delay relay has a 70 second delay to be sure of complete engine shutdown.

Water Temperature Contactor Switch - This contactor switch is a separate unit that is wired into the shutdown circuit. It has an element that feels the temperature of the coolant (it must be in contact with the coolant). When the engine coolant temperature becomes too high, the switch closes to cause the fuel to be shut off to the engine. The switch is installed in the top front of the cylinder head.

Engine Oil Pressure Switch - This switch is installed in the main oil gallery on the right side of the cylinder block. The oil pressure switch is used to determine low engine oil pressure and to activate the time delay relay.

Wiring Diagrams - Abbreviations, wire codes and recommended wire sizes, used with the wiring diagrams that follow, can be found at the front of the WIRING DIAGRAMS SECTION.

The notes that follow are used with the wiring diagrams shown in this section.

CUSTOMER TO FURNISH BATTERY AND ALL WIRES SHOWN DOTTED

NOTE A: Optional ground to engine may be used with grounded systems only.

NOTE B: These leads terminate at the starter motor and must be omitted when there is no starter motor. In this case customer must provide DC power at the other termination point of these two leads.

NOTE C: If 2301 Governor is used, only one magnetic pickup is required. Use magnetic pickup from overspeed group. Wire magnetic pickup to speed switch. Then wire from speed switch to the 2301 Governor. The speed switch may be installed physically near the 2301 if desired.

NOTE D: Electronic dual speed switch and electronic time delay relay can be wired to battery power continuously since the system will draw less than 40 MA current when the engine is not running.

NOTE E: If required, customer is to supply (RNS) Remote Normal Shutdown Switch. Requires a single pole N.O. switch with a minimum contact rating of 5 amps inductive at the charging system voltage. Can be a latching switch if customer prefers. Shuts off engine fuel when activated.

NOTE F: If required, customer is to supply (RESS) Remote Emergency Shutdown Switch. Requires a single pole N.O. switch with a minimum contact rating of 5 amps inductive at the charging system voltage. Can be latching switch if customer prefers. Shuts off engine air and fuel when activated. This shut-off mode must not be used for normal engine shutdown.

Water Temperature And Oil Pressure Shutoff System (With Time Delay Relay)

WIRING DIAGRAM (Fuel Shutoff Solenoid Energized to Shutoff)
1. Time delay relay. 2. Oil pressure switch. 3. Water temperature switch. 4. Switch (N.O.). 5. Circuit breaker. 6. Shutdown relay. 7. Battery. 8. Diode assembly. 9. Shutoff solenoid. 10. Starter motor.

When the engine starts, engine oil pressure will close the N.O. switch and open the N.C. switch in oil pressure switch (2). This completes the circuit to time delay relay (1). N.O. switch (4) in the time delay relay now closes and completes the circuit between shutdown relay (6) and terminal TD-7 of the time delay relay.

If the engine coolant temperature goes above the setting of water temperature switch (3), the N.O. contacts will close. This lets current flow through water temperature switch (3) and through switch (4) to activate shutdown relay (6) which in turn activates fuel shutoff solenoid (9). When the engine stops, engine oil pressure will become less than the setting of the oil pressure switch. The N.O. switch will open and stop the flow of current to the time delay relay. This will start the time delay relay timer. After 70 seconds, switch (4) will open to stop current flow through shutdown relay (6). Now, fuel shutoff solenoid (9) will no longer be activated.

If engine oil pressure gets less than the setting of the oil pressure switch, the N.C. switch will close. This will let current flow through switch (4) to activate shutdown relay (6) which in turn activates fuel shutoff solenoid (9). The N.O. switch will open and start the time delay relay timer. After 70 seconds, switch (4) will open to stop current flow through shutdown relay (6). Now, fuel shutoff solenoid (9) will no longer be activated.

Water Temperature, Oil Pressure And Electronic Overspeed Shutoff System (With Time Delay Relay)

WIRING DIAGRAM (Fuel Shutoff Solenoid Energized to Shutoff)
1. Magnetic pickup. 2. Dual speed switch. 3. Overspeed switch. 4. Crank terminate switch. 5. Water temperature switch. 6. Oil pressure switch. 7. Time delay relay. 8. Switch (N.O.). 9. Shutdown relay. 10. Battery. 11. Diode assembly. 12. Shutoff solenoid. 13. Starter motor.

The engine speed is felt by magnetic pickup (1). As the teeth of the flywheel go through the magnetic lines of force around the pickup, an AC voltage is made. Dual speed switch (2) measures engine speed from the frequency of the voltage.

Time delay relay (7) controls the operation of shutdown relay (9), which in turn, controls the operation of fuel shutoff solenoid (12). Time delay relay (7) will keep the fuel shutoff solenoid energized for 70 seconds after a fault condition. This prevents the engine from being started again before the flywheel has stopped rotation.

When the engine starts and gets to a speed just above cranking speed, the normally open contacts of crank terminate switch (4) [which is part of dual speed switch (2)] will close. This will complete the circuit to time delay relay (7) through terminal TD-2. In approximately 9 seconds N.O. switch (8) in time delay relay (7) will close and complete the circuit between shutdown relay (9) and terminal TD-7 of the time delay relay. If the engine oil pressure has not activated oil pressure switch (6) by 9 seconds, current will flow through the N.C. switch in the oil pressure switch and through the now closed N.O. switch (8) to activate shutdown relay (9) which in turn activates fuel shutoff solenoid (12). If engine oil pressure activates oil pressure switch (6), the N.O. switch will close and the N.C. switch will open. This will let current flow to terminal TD-1 of the time delay relay and immediately close N.O. switch (8). At the same time the N.C. switch in the oil pressure switch will open and prevent current flow to switch (8).

If the engine speed increases above the overspeed setting (118% of rated speed) of the dual speed switch, the overspeed switch (part of the dual speed switch) will close across terminals DSS-7 and DSS-8. This completes the circuit to shutdown relay (6) through the now closed switch (8) at terminal TD-7. Shutdown relay (9) is activated and in turn activates fuel shutoff solenoid (12) to cause the engine to shutdown.

When the engine speed gets less than the cranking speed setting, switch (4) opens. This stops the flow of current to terminal TD-2 of the time delay relay. When the engine stops, engine oil pressure will become less than the setting of the oil pressure will become less than the setting of the oil pressure switch. The N.O. switch will open and stop the flow of current to terminal TD-1 of the time delay relay. This will start the time delay relay timer. After 70 seconds, switch (8) will open and stop current flow to shutdown relay (9) and fuel shutoff solenoid (12) will no longer be activated.

After an overspeed shutdown, a button on the dual speed switch must be pushed to open the overspeed switch before the engine will run.

When the engine has been started and is running, the time delay relay will close switch (8). If the engine coolant temperature goes above the setting of water temperature switch (5), the N.O. contacts will close. This lets current flow through the water temperature switch and through switch (8) to activate shutdown relay (9) and in turn activates fuel shutoff solenoid (12).

When the engine speed gets less than the cranking speed setting, switch (4) opens. This stops the flow of current to terminal TD-2 of the time delay relay. When the engine stops, engine oil pressure will become less than the setting of the oil pressure switch. The N.O. switch will open and stop the the flow of current to terminal TD-1 of the time delay relay. This will start the time delay relay timer. After 70 seconds, switch (8) will open and stop current flow to shutdown relay (9) and fuel shutoff solenoid (12) will no longer be activated.

When the engine has been started and is running, the time delay relay will close switch (8). If the engine oil pressure gets less than the setting of oil pressure switch (6), the N.C. switch will close. This will let current flow through switch (8) to activate shutdown relay (9) and in turn activates fuel shutoff solenoid (12). The N.O. switch will also open and stop current flow to terminal TD-1 of the time delay relay. When the engine speed gets less than the cranking speed setting, switch (4) opens. This stops the flow of current to terminal TD-2 of the time delay relay and starts the time delay relay timer. After 70 seconds, switch (8) will open and stop current flow to shutdown relay (9) and fuel shutoff solenoid (12) will no longer be activated.

Water Temperature, Oil Pressure And Electronic Overspeed With Air Shutoff (With Time Delay Relay)

WIRING DIAGRAM (Fuel Shutoff Solenoid Energized to Shutoff)
1. Magnetic pickup. 2. Dual speed switch. 3. Overspeed switch. 4. Crank terminate switch. 5. Water temperature switch. 6. Oil pressure switch. 7. Time delay relay. 8. Switch (N.O.). 9. Fuel shutdown relay. 10. Diode. 11. Air shutdown relay. 12. Fuel shutoff solenoid. 13. Air shutoff solenoid. 14. Starter motor. 15. Battery.

This system gives high water temperature, low oil pressure and overspeed protection. The air inlet shutoff system is used with fuel shutoff system to give overspeed protection to the engine and is activated only by an overspeed condition. The air inlet shutoff system consists of diode (10), shutdown relay (11), solenoid (13) and a shutoff valve. The location of the shutoff valve and shutoff solenoid is in the air inlet pipe to the engine.

When an engine has an overspeed condition the air shutoff shutdown relay (11) is activated by the same signal from time delay relay (7) that activates fuel shutdown relay (9).

See WATER TEMPERATURE, OIL PRESSURE AND ELECTRONIC OVERSPEED SHUTOFF SYSTEM for more details of the systems operation.

After an overspeed condition, a reset button on the dual speed switch must be pushed to open the overspeed switch and the air inlet shutoff valves must be manually reset before the engine will run.

Diode (10) keeps the air shutoff solenoid circuit separate from the fuel shutoff circuit. This lets a manual shutdown switch be connected to fuel shutdown relay (9) and does not activate air shutdown relay (11) when the switch is closed to manually shutdown the engine.

Electronic Overspeed Shutoff System (With Time Delay Relay)

WIRING DIAGRAM (Fuel Shutoff Solenoid Energized to Shutoff)
1. Magnetic pickup. 2. Crank terminate switch. 3. Dual speed switch. 4. Time delay relay. 5. Switch (N.O.). 6. Shutdown relay. 7. Battery. 8. Diode assembly. 9. Shutoff solenoid. 10. Starter motor.

The engine speed is felt by magnetic pickup (1). As the teeth of the flywheel go through the magnetic lines of force around the pickup, an AC voltage is made. Dual speed switch (3) measures engine speed from the frequency of this AC voltage.

Time delay relay (4) controls the operation of shutdown relay (6), which in turn, controls the operation of fuel shutoff solenoid (9). Time delay relay (4) will keep the fuel shutoff solenoid energized for 70 seconds after a fault condition. This prevents the engine from being started again before the flywheel has stopped rotation.

When the engine starts and gets to a speed just above cranking speed, the normally open contacts of crank terminate switch (2) [which is part of dual speed switch (3)] will close. This will complete the circuit to time delay relay (4) through terminal TD-1. Normally open switch (5) in time delay relay (4) now closes and completes the circuit between shutdown relay (6) and terminal TD-7.

If the engine speed increases above the overspeed setting (118% of rated speed) of the dual speed switch, the overspeed switch (part of the dual speed switch) will close across terminals DSS-7 and DSS-8. This completes the circuit to shutdown relay (6) through the now closed switch (5) at terminal TD-7. Shutdown relay (6) is activated and in turn activates fuel shutoff solenoid (9) to cause the engine to shutdown.

When the engine stops, crank terminate switch (2) will open the circuit across terminals DSS-10 and DSS-11. This stops current flow to time delay relay (4). Now, the time delay relay timer is started and 70 seconds later, switch (5) will open the circuit at terminal TD-7. Current flow is then stopped through shutdown relay (6) and fuel shutoff solenoid (9) will no longer be activated.

A reset button on the dual speed switch must be pushed to open the overspeed switch before the engine will run.

Electronic Overspeed With Air Shutoff (With Time Delay Relay)

WIRING DIAGRAM (Fuel Shutoff Solenoid Energized to Shutoff)
1. Magnetic pickup. 2. Crank terminate switch. 3. Dual speed switch. 4. Time delay relay. 5. Switch (N.O.). 6. Fuel shutdown relay. 7. Diode. 8. Air shutdown relay. 9. Fuel shutoff solenoid. 10. Air shutoff solenoid. 11. Starter motor. 12. Battery.

The air inlet shutoff system is used with the fuel shutoff system to give overspeed protection to the engine. The air inlet shutoff system consists of diode (7), shutdown relay (8), solenoid (10) and a shutoff valve. The location of the shutoff valve and shutoff solenoid is in the air inlet pipe to the engine.

When an engine has an overspeed condition, the air shutoff shutdown relay (8) is activated by the same signal from time delay relay (4) that activates fuel shutdown relay (6). See ELECTRONIC OVERSPEED SHUTOFF SYSTEM for details of the system operation.

After an overspeed condition, a reset button on the dual speed switch must be pushed to open the overspeed switch and the air inlet shutoff valves must be manually reset before the engine will run.

Diode (7) keeps the air shutoff solenoid circuit separate from the fuel shutoff solenoid circuit. This lets a manual switch be connected to fuel shutdown relay (6) and does not activate air shudown relay (8) when the switch is closed to manually shutdown the engine.

Alarm Contactor System

WIRING DIAGRAM
1. Oil pressure switch. 2. Water temperature contactor. 3. Source voltage. 4. Toggle switch (optional). 5. Alarm. 6. Signal lights.

If the oil pressure is too low or the water temperature is too high this system will activate alarm (5) and signal lights (6).

Before the engine is started it will be necessary to override oil pressure switch (1) or the alarm will activate. This is done by either a manual override button on the (earlier) oil pressure switch or toggle switch (4). Oil pressure will return the manual override button to the run position. The toggle switch must be manually closed when the engine has oil pressure.

WIRING DIAGRAM
1. Oil pressure switch. 2. Water temperature contactor. 3. Source voltage. 4. Toggle switch (optional). 6. Signal lights (three). 7. Air temperature contactor.

If the oil pressure is too low or the water temperature is too high this system will activate signal lights (6).

Before the engine is started it will be necessary to override oil pressure switch (1) or the signal lights will activate. This is done by either a manual override button on the (earlier) oil pressure switch or toggle switch (4). Oil pressure will return the manual override button to the run position. The toggle switch must be manually closed when the engine has oil pressure.

WIRING DIAGRAM
1. Oil pressure switch. 2. Water temperature contactor. 3. Source voltage. 4. Toggle switch (optional). 5. Alarm. 7. Air temperature contactor.

If the oil pressure is too low or the water temperature is too high this system will activate alarm (5).

Before the engine is started it will be necessary to override oil pressure switch (1) or the alarm will activate. This is done by either a manual override button on the (earlier) oil pressure switch or toggle switch (4). Oil pressure will return the manual override button to the run position. The toggle switch must be manually closed when the engine has oil pressure.

Water Temperature And Oil Pressure Shutoff System (With Oil Pressure Delay Or Fuel Pressure Switch)

WIRING DIAGRAM
1. Oil pressure switch. 2. Water temperature contactor. 3. Oil pressure (time delay) or fuel pressure switch. 4. Rack solenoid. 5. Diode assembly. 6. Starter. 7. Battery.

If the oil pressure is too low or the coolant temperature is too high this system will activate rack solenoid (4). The solenoid is connected to the fuel rack by linkage. When it is activated it will move to stop the flow of fuel to the engine. The engine will stop.

Before the engine can be started it will be necessary to push the manual override button on (earlier) oil pressure switch (1). Oil pressure will return the manual override button to the run position.

Diode assembly (5) is used to stop arcing, for protection of the system.

Oil pressure delay or fuel pressure switch (3) is used to prevent discharge of battery (7) through the solenoid when the engine is stopped.

Electronic Overspeed Shutoff System (With Oil Pressure Delay Or Fuel Pressure Switch)

WIRING DIAGRAM
1. Rack solenoid. 2. Oil pressure (time delay) or fuel pressure switch. 3. Dual speed switch. 4. Magnetic pickup. 5. Diode assembly. 6. Starter. 7. Battery.

The engine speed is felt by magnetic pickup (4). As the teeth of the flywheel go through the magnetic lines of force around the pickup, an AC voltage is made. Dual speed switch (3) measures engine speed from the frequency of this AC voltage.

Rack solenoid (1) is connected to the fuel rack by linkage. When it is activated, it will move to stop the flow of fuel to the engine.

If the engine speed increases above the overspeed setting (118% of rated speed) of the dual speed switch, the overspeed switch [which is part of dual speed switch (3)] will close across terminals DSS-7 and DSS-8. This completes the circuit to rack solenoid (1) through the now closed pressure switch (2) and activates the solenoid to shutdown the engine.

After an overspeed shutdown, a button on the dual speed switch must be pushed to open the overspeed switch before the engine will run.

Diode assembly (5) is used to stop arcing, for protection of the system.

An oil pressure (time delay) or fuel pressure switch (2) is used to prevent discharge of battery (7) through the solenoid when the engine is stopped. The dual speed switch can be connected to the battery constantly because it uses less than 20 MA of current when the engine is stopped.

Electronic Overspeed With Air Shutoff (With Oil Pressure Delay Or Fuel Pressure Switch)

WIRING DIAGRAM
1. Rack solenoid. 2. Oil pressure (time delay) or fuel pressure switch. 3. Dual speed switch. 4. Magnetic pickup. 5. Diode assembly. 6. Diode. 7. Air shutoff solenoids. 8. Starter motor. 9. Battery.

This system gives overspeed protection. Air shutoff solenoids (7) control a valve assembly in the air inlet pipe. When the solenoids are activated, the valve closes to shutoff air to the engine. When the engine has an overspeed condition, the air shutoff solenoids are activated by the same signal from the overspeed switch [part of dual speed switch (3)] that activates rack solenoid (1). See ELECTRONIC OVERSPEED SHUTOFF SYSTEM for more detail of the system operation.

Diode assemblies (5) are used to stop arcing, for protection of the system.

Diode (6) keeps the air shutoff solenoid circuit separate from the rack solenoid circuit. For example, if a manual switch was connected to the rack solenoid, the air shutoff solenoids would not activate when the switch was closed.

After an overspeed condition, a reset button on the dual speed switch must be pushed to open the overspeed switch and the air inlet shutoff valves must be manually reset before the engine will run.

Water Temperature, Oil Pressure And Electronic Overspeed Shutoff System (With Oil Pressure Delay Or Fuel Pressure Switch)

WIRING DIAGRAM
1. Oil pressure switch. 2. Oil pressure (time delay) or fuel pressure switch. 3. Water temperature contactor. 4. Dual speed switch. 5. Magnetic pickup. 6. Rack solenoid. 7. Diode assembly. 8. Starter motor. 9. Battery.

This system gives high water temperature, low oil pressure and overspeed protection to the engine.

Rack solenoid (6) is connected to the fuel rack by linkage. When it is activated it will move to stop the flow of fuel to the engine. The rack solenoid can be activated by oil pressure switch (1), water temperature contactor (3) or the overspeed switch that is part of dual speed switch (4).

If the oil pressure is too low or the coolant temperature is too high, oil pressure switch (1) or water temperature contactor (3) will close to complete the circuit and activate rack solenoid (6).

The engine speed is felt by magnetic pickup (5). As the teeth of the flywheel go through the magnetic lines of force around the pickup, an AC voltage is made. Dual speed switch (4) measures engine speed from the frequency of this AC voltage.

If the engine speed increases above the overspeed setting (118% of rated speed) of the dual speed switch, the overspeed switch [which is part of dual speed switch (4)] will close across terminals DSS-7 and DSS-8. This completes the circuit to rack solenoid (6) through pressure switch (2) and water temperature contactor (3) to activate the solenoid and shutdown the engine.

After an overspeed shutdown, a button on the dual speed switch must be pushed to open the overspeed switch before the engine will run.

Diode assembly (7) is used to stop arcing, for protection of the system.

An oil pressure (time delay) or fuel pressure switch (2) is used to prevent discharge of battery (9) through the solenoid when the engine is stopped. The dual speed switch can be connected to the battery constantly because it uses less than 20 MA of current when the engine is stopped.

Water Temperature, Oil Pressure And Electronic Overspeed With Air Shutoff (With Oil Pressure Delay Or Fuel Pressure Switch)

WIRING DIAGRAM
1. Oil pressure switch. 2. Oil pressure (time delay) or fuel pressure switch. 3. Water temperature contactor. 4. Dual speed switch. 5. Magnetic pickup. 6. Rack solenoid. 7. Diode assembly. 8. Diode. 9. Air shutoff solenoids. 10. Starter motor. 11. Battery.

This system gives high water temperature, low oil pressure and overspeed protection. The air inlet shutoff system is used with the fuel shutoff to give overspeed protection to the engine and is activated only by an overspeed condition. The air inlet shutoff system consists of diode (8), solenoid (9) and a shutoff valve. The location of the shutoff valve and shutoff solenoid is in the air inlet pipe to the engine. Engines with two turbochargers have two shutoff valves and solenoids.

When an engine has an overspeed condition air shutoff solenoid (9) is activated by the same signal from the overspeed switch [which is part of dual speed switch (4)] that activates rack solenoid (6).

See WATER TEMPERATURE, OIL PRESSURE AND ELECTRONIC OVERSPEED SHUTOFF SYSTEM for more details of the systems operation.

After an overspeed condition, a reset button on the dual speed switch must be pushed to open the overspeed switch and the air inlet shutoff valves must be manually reset before the engine will run.

Diode (8) keeps the air shutoff solenoid circuit separate from the fuel shutoff circuit. This lets a manual shutdown switch be connected to rack solenoid (6) and does not activate air shutoff solenoid (9) when the switch is closed to manually shutdown the engine.

NOTE: On systems that use an earlier type oil pressure switch, it will be necessary to push the manual override button before the engine can be started. Oil pressure will return the manual override button to the run position.

Mechanical Oil Pressure And Water Temperature Shutoff

MECHANICAL OIL PRESSURE AND WATER TEMPERATURE SHUTOFF
1. Water temperature shutoff. 2. Shutoff lever. 3. Spring. 4. Piston. 5. Port. 6. Control lever. 7. Oil pressure shutoff.

Oil pressure shutoff (7) is fastened to the governor. Control lever (6) is connected by a shaft to shutoff lever (2). The shutoff lever is connected by linkage to the fuel rack.

Before the engine is started the control lever is used to push the shutoff lever against piston (4). The shutoff lever moves the piston back and puts spring (3) in compression. With the shutoff lever in this position the engine can be started.

When the engine starts, pressure oil will flow through port (5) into the space between the piston and the housing. When the oil pressure is high enough, it will hold the piston in position. As long as the engine has enough oil pressure, the fuel rack can be controlled by the governor.

If the oil pressure gets too low the force of compression in the spring will move the piston against the shutoff lever. The shutoff lever will move the fuel rack to stop the flow of fuel to the engine. The engine will stop.

Water temperature shutoff (1) is a control valve for the oil pressure shutoff.

When the water temperature becomes too high, thermostat assembly (10) causes stem (9) to move ball (11) off of its seat. Pressure oil at inlet port (8) will go through the valve and drain into the engine crankcase. This will cause the oil pressure to decrease. The oil pressure shutoff will activate and stop the engine.

TEMPERATURE SHUTOFF
8. Inlet port. 9. Stem. 10. Thermostat assembly. 11. Ball.

Shutoff And Alarm System Components

Oil Pressure Switch

Micro Switch Type

The oil pressure switch is used to give protection to the engine from damage because of low oil pressure. When oil pressure lowers to the pressure specifications of the switch, the switch closes and activates the rack shutoff solenoid.

On automatic start/stop installations, this switch closes to remove the starting system from the circuit when the engine is running with normal oil pressure.

This switch for oil pressure can be connected in a warning system for indication of low oil pressure with a light or horn.

As pressure of the oil in bellows (6) becomes higher, arm (4) is moved against the force of spring (3). When projection (10) of arm (4) makes contact with arm (9), pressure in the bellows moves both arms. This also moves button (8) of the micro switch to activate the micro switch.

OIL PRESSURE SWITCH (Micro Switch Type)
1. Locknut. 2. Adjustment screw. 3. Spring. 4. Arm. 5. Spring. 6. Bellows. 7. Latch plate. 8. Button for micro switch. 9. Arm. 10. Projection of arm.

Some of these switches have a "Set For Start" button. When the button is pushed in, the micro switch is in the START position. This is done because latch plate (7) holds arm (9) against button (8) of the micro switch and the switch operates as if the oil pressure was normal. When the engine is started, pressure oil flows into bellows (6). The bellows move arm (4) into contact with latch plate (7). The latch plate releases the "Set For Start" button and spring (5) moves it to the RUN position. This puts the switch in a ready to operate condition.

Pressure Switch

Pressure switches are are used for several purposes and are available with different specifications. They are used in the oil system and in the fuel system. One use of the switch is to open the circuit between the battery and the rack shutoff solenoid after the oil pressure is below the pressure specifications of the switch. It also closes when the engine starts.

Another use of the switch is to close and activate the battery charging circuit when the pressure is above the pressure specification of the switch. It also disconnects the circuit when the engine is stopped.

Switches of this type have three terminal connections. They are used to do two operations with one switch. They open one circuit and close another with the single switch.

Shutoff Solenoid

A shutoff solenoid changes electrical input into mechanical output. It is used to move the fuel injection pump rack to the off position. It can also be used to move a valve assembly in the air inlet pipe to a closed position. This stops the engine.

The shutoff solenoid can be activated by any one of the many sources. The most usual are: water temperature contactor, oil pressure switch, overspeed switch and remote manual control switch.

RACK SHUTOFF SOLENOID (Typical Illustration)

Water Temperature Contactor Switch

The contactor switch for water temperature is installed in the water manifold. No adjustment to the temperature range of the contactor can be made. The element feels the temperature of the coolant and then operates the micro switch in the contact when the coolant temperature is too high, the element must be in contact with the coolant to operate correctly. If the cause for the engine being too hot is because of low coolant level or no coolant, the contactor switch will not operate.

The contactor switch is connected to the rack shutoff solenoid to stop the engine. The switch can also be connected to an alarm system. When the temperature of the coolant lowers to the operating range, the contactor switch opens automatically.

WATER TEMPERATURE CONTACTOR SWITCH

Circuit Breaker

The circuit breaker gives protection to an electrical circuit. Circuit breakers are rated as to how much current they will permit to flow. If the current in a circuit gets too high it will cause heat in disc (3). Heat will cause distortion of the disc and contacts (2) will open. No current will flow in the circuit.

CIRCUIT BREAKER SCHEMATIC
1. Disc in open position. 2. Contacts. 3. Disc. 4. Circuit terminals.

An open circuit breaker will close (reset) automatically when it becomes cooler.

Electronic Speed Switch

The electronic speed switch (dual speed switch) activates the shutoff solenoid when the engine speed gets approximately 18% higher than the rated full load speed of the engine. It also stops current flow to the starter motor after the engine starts.

The electronic speed switch makes a comparison between the output frequency of the magnetic pickup and the setting of the electronic speed switch. When they are equal, the normally open contacts in the electronic speed switch close. Lamp (2) will go on. The switch also has a failsafe circuit that will cause the engine to shutdown if there is an open in the magnetic pickup circuit.

When the engine is stopped, it will be necessary to push reset button (1), before the engine can be started.

ELECTRONIC SPEED SWITCH
1. Reset button. 2. Lamp.

Power Take-Off Clutches

POWER TAKE-OFF CLUTCH (Typical Illustration)
1. Ring. 2. Driven discs. 3. Link assemblies. 4. Lever. 5. Key. 6. Collar assembly. 7. Nut. 8. Yoke assembly. 9. Hub. 10. Plates. 11. Output shaft.

Power take-off clutches (PTO's) are used to send power from the engine to accessory components. For example, a PTO can be used to drive an air compressor or a water pump.

The PTO is driven by a ring (1) that has spline teeth around the inside diameter. The ring can be connected to the front or rear of the engine crankshaft by an adapter.

NOTE: On some PTO's located at the rear of the engine, ring (1) is a part of the flywheel.

The spline teeth on the ring engage with the spline teeth on the outside diameter of driven discs (2). When lever (4) is moved to the ENGAGED position, yoke assembly (8) moves collar assembly (6) in the direction of the engine. The collar assembly is connected to four link assemblies (3). The action of the link assemblies will hold the faces of driven discs (2), drive plates (10) and hub (9) tight together. Friction between these faces permits the flow of torque from ring (1), through driven discs (2), to plates (10) and hub (9), Spline teeth on the inside diameter of the plates drive the hub. The hub is held in position on the output shaft (11) by a taper, nut (7) and key (5).

NOTE: A PTO can have from one to three driven discs (2) with a respective number of plates.

When lever (4) is moved to the NOT ENGAGED position, yoke assembly (8) moves collar assembly (6) to the left. The movement of the collar assembly will release link assemblies (3). With the link assemblies released there will not be enough friction between the faces of the clutch assembly to permit a flow of torque.