INSTRUCT IONS

for

ELECTRIC-HYDRAULIC GOVERNOR SYSTEM

used on

DIESEL ENGINES

Cummins Engine Company

Model No. V-378-C (V-6)

Made I No. V-504-C210 (V-8)

Detroit Diesel Engine Division

Model No. 305X (3-71N) (3-IN-LINE)

Model No. 4055C (4-71N) (4-IN-LINE)

MOTOR GENERATOR DIVISfON

HOBART BROTHERS COMPANY

TROY, OHIO 45373

U.S.A.

l-68

022873

INTRODUCTION .,

This manual contains operation, maintenance, adiustment , and trouble shooting information

for an electric-hydraulic governor system used on certain diesel engines. The system is

identified as a Woodward, 2301.

Instructions cover two basic applications of the governor. They apply to installations.on

Cummins, V-6 and V-8 engines, and Detroit Diesel, in-line 3 and 4 cylinder engines.

Any information which applies to only one installation will be qualified and identified

as such.

The manual is not intended to be a text book on electricity or electronics. Its primary

purpose is to provide information and instructions to experienced operators, electricians,

and mechanics who have never seen, operated, or serviced an electric-hydraulic governor.

The manual should be read completely before attempting to operate, adjust, or trouble

shoot the system.

The manual is divided into three chapters. Each chapter is divided into as many sections

as required., Each new section starts with page 1, and illustrations within each section are

identified consecutively from Figure 1 through as many as required. To reference material

to be found in another section, it is referred to by chapter-section, and paragraph or figure

number.

Introduction

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FOBART D : iMOTOR GENERATOR DIVISION D % QD : HOBI\RT BROTHERS COMPANY % Q. Bl++

Introduction Feb 28/73

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iMOTOR GENERATOR DlVlSlON

“c 2 HOBART BROTHERS CCIMPANY b . B &,d

SUBJECT

Description/Operation

Description

General

TABLE OF CONTENTS

Electric-Hydraulic Governor System Components

Electric Control Unit

Hydraulic Actuator

Magnetic Pickup

Miscel Ianeous Equipment

Operation

General

Starting, Operating, and Stopping the Engine

Servicing

Maintenance

General

Inspection

Lubrication

Periodic Maintenance

Replace Hydraulic Actuator

Remove Actuator

lnstal I Actuator

Replace Electric Control Box

Remove Control Box

CHAPTER/SECT ION PAGE

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Contents

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SUBJECT

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TABLE 0~ CONTENTS (C~NT’D.)

Install Control Box

Replace Magnetic Pickup

Adjustment

General

Contents Feb 28/73

Page 2 mp :‘:

CHAPTER/SECTION

Actuator Linkage Adjustment

Geneial

Adjust Actuator Linkage on Cummins Engines

Adiust Actuator Linkage on Detroit Diesel Engines

Magnetic Pickup Adjustment

General

Adiustment Procedures

Hydraulic Actuator Adjustment

General

Adjustment Procedures

Electric Control Box Adiustment

General

Adjustment Procedures

Trouble Shooting

Theory of Operation

General

Basic Theory of Operation

Trouble Shooting Procedures

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;MOTOR GENERATOR DIVISION HOBART EmOTHERS COMPANY

TABLE OF CONTENTS (CONT’D.)

SUBJECT CHAPTER/SECTION

General 3-2

Trouble Shooting Chart

Description

Use of Trouble Shooting Chart

Equipment for Trouble Shooting

Safety

Connections and Leads

Trouble Shooting Guides

LIST OF ILLUSTRATIONS

CHAPTER/ FIGURE

SECT ION NUMBER

l-l 1 Electric Control Box (Old Style)

l-l 2 Electric Control Box (New Style “Fail-Safe”)

l-l 3 Hydraui ic Actuator

l-l 4 Magnetic Pickup

2-l 1 Actuator Installation on Cummins Engine

2-l 2 Actuator Installation on Detroit Diesel Engine

2-l 3 Control Box Installation on All Units Except

Self-Propelled

2-l 4 Control Box Installation on Self-Propelled Units

2-l 5 Magnetic Pickup lnstal Iation on Cummins Engines

2-2 1

2-2 2

2-2 3

2-2 4

2-2 5

2-2 6

2-2 7

TITLE

Actuator Linkage, Cummins Engines

Actuator Linkage, Detroit Diesel Engines

Magnetic Pickup

Hydraulic Actuator Adjustment

Actuator Test Circuit

Electric Control Box and Potentiometer (Original,

Old Type)

PAGE

1

1

1

1

1

1

2

2

PAGE

NO.

2

2

4

4

5

9

Electric Control Box and Potentiometer (New Fail-Safe

TY P”) 10

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Contents

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CHAPTER/ FIGURE

SECTION NUMBER

3-l 1

3-l 2

3-2 1 Electric Governor Voltage Values 3-2 2 Trouble Shooting Chart

HOBART I I QB

iMOTOR GENERATOR DIVISION

“c 2 HOBw?T BRcnHERS CCIMPANY % Q . B ,I+”

LIST OF ILLUSTRATIONS (CONT’D .)

TITLE

Actuator Cross-Section

Speed Setting Potentiometer Schematic

PAGE

NO.

3

4

3

4-5

Contents

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CHAPTER 1. DESCRlPTlON/OPERAT ION

SECTION 1. DESCRIPTION

1. General

The electric-hydraulic governor system is installed on engine-driven generator sets by

Hobart Brothers Company to replace conventional, mechanical type governors. This

system for control of engine speed (and generator output frequency) was selected for

this application because it provides constant speed, and faster engine response to

changes in load conditions, which result in much closer frequency control.

2. Electric-Hydraulic Governor System Components

The governor system consists of the following main components:

Electric control unit with potentiometer

Hydraulic actuator

Magnetic pickup

A. Electric Control Unit (See Figures 1 and 2)

The electric control unit (Fig. 1) is a compact assembly of solid state components

enclosed in a metal box. Two adjustments, “gain” and “reset droop”, are provided

for adiustment of response time and stability. An externally mounted potentiometer

provides adjustment for engine speed. The function of the control unit is to compare

a signal from the speed setting potentiometer to a signal from the speed-sensing

magnetic pickup and as a result of this comparison, to send a signal to the hydraulic

actuator which will cause the actuator to increase, decrease, or hold engine speed

steady as required. A newer, “fail-safe”, control unit (Fig. 2) is now available.

It is somewhat different in appearance in that “gain” and “reset droop” adjustments

are relocated. It is easily recognizable by the absence of a diode connected

between terminals No. 1 and No. 8. The newer control unit has “fail-safe”

capability which means that the engine will not overspeed in case of input signal

(AC magnetic pickup or DC power) failure. Hereafter the electric control unit

will be referred to as the control box.

B. Hydraulic Actuator (See Figure 3)

The function of the hydraulic actuator is to position the engine speed-control lever

as required to maintain a constant engine speed regardless of load conditions. The

output shaft (and lever) of the actuator is mechanically connected through a Iink-

age arrangement to the fuel pump speed-control lever on Cummins engines, and to

the injector rack speed-control lever on Detroit Diesel engines. Hydraulic power

for operation of the actuator is supplied by the engines’ fuel pressure system.

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Electric Control Box (Old Style)

Figure 1

Electric Contml Box (New Style “Fail-Safe”)

Figure 2 t

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Operation of the actuator is controlled by a 12-V DC signal from the control

bOX.

Hydraulic Actuator

Figure 3

C. Magnetic Pickup (See Figure 4)

The magnetic pickup is a device for detecting the speed of the engine. It is

mounted in the flywheel housing directly over the ring gear. It generates an AC signal when the flywheel teeth pass through the magnetic field at the end of the

pickup. This signal is conducted to the control box through a coaxial cable.

The control box uses the AC signal to electronically determine whether engine

speed should be increased, decreased, or held steady to meet predetermined

speed requirements.

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Magnetic Pickup

Figure 4 t

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D. Miscellaneous Equipment

In addition to main components described above, the system requires a shielded

coaxial cable between the magnetic pickup and control box, governor throttle

linkage, mounting brackets, and other miscellaneous hardware and wiring.

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SECTION 2. OPERAT’ION

1. General

From an operator’s viewpoint, operation of the electric-hydraulic governor is very

simple. To give the governor system full control of engine speed, it is only necessary

to apply 12-V DC to the control box by operating a switch as instructed in the basic

generator set manual.

2. Starting, Operating , and Stopping the Engine

Refer to the Generator Set Manual for all engine operating procedures.

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CHAPTER 2. SERVICING

SECTION 1. MAINTENANCE

1. General

To make certain the governor system is ready for operation at al I times, it must be in-

spected and checked systematically, and regularly, so that defects may be discovered

and corrected before they result in failure of the equipment.

2. Inspection

A periodic inspection schedule should be established and maintained. Throttle linkage

should be checked at least every two weeks, or after each 100 hours of operation. ln-

spect for free operation throughout the full travel of the linkage’. Check the security

of all linkage attaching and adiusting hardware.

Check all electrical connections at the control box and at the actuator.

Check tube and hose fittings for leaks.

3. Lubrication

Engine fuel oil supplies sufficient lubrication for the actuator. No additional lubrication

is required.

4. Periodic Maintenance

Other than inspections and checks described above, no periodic maintenance is re-

quired.

5. Replace Hydraulic Actuator

Figure 1 illustrates an actuator installation on a Cummins engine. Figure 2 represents

an installation on a Detroit Diesel engine.

A. Remove Actuator

(1) Observe and mentally note the color and location of wire leads at the actuator.

Disconnect leads and cable shield ground.

(2) Disconnect input fuel oil tube and drain hose.

(3) Disconnect governor rod from actuator lever at ball-joint.

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Actuator Installation on Cummins Engine

Figure 1

Actuator Installation on Detroit Diesel Engine

Figure 2

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(4) Remove two actuator mounting screws and lift off the actuator.

B. Instal I Actuator

(1) Position actuator on mounting bracket and align mounting holes. Install

mounting screws and tighten securely.

(2) Attach governor rod ball-ioint to actuator lever. Actuate linkage to check

for free operation.

(3) Connect input tube and drain hose.

(4) Connect leads at input terminals. Ground the cable shielding with an actuator

cover screw.

NOTE: Check Generator Set connection or schematic diagrams if

necessary to be certain of correct wiring.

(5) If actuator lever was removed or disturbed, check and adjust governor linkage

in accordance with Sect. 2-2, Para. 2, B, or C.

6. Replace Electric Control Box

The electric control.box is mounted on a vertical panel which is attached to the lifting

frame on al I units except the self-propel led type machines (see Fig. 3).

On self-propelled units the electric control box is mounted on the floor of the main

control box behind the instrument panel (see Fig. 4).

NOTE: On ail current “B” Specifications the electric control box is mounted

on the rear panel of the main control box.

A. Remove Control Box

(1) ldentify six input and output leads and carefully disconnect (see 2-2, Figs.

5 and 6). Leave reverse polarity diode and potentiometer leads attached (if

so equipped).

(2) Disconnect grounded shielding. Remove box attaching hardware and remove

box. Do not loose rubber mounts.

8. Install Control Box

(1) Carefully position box on rubber mounts and install attaching hardware.

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Control Box Installation on All Units Except

Self-Propelled

Figure 3

Contml Box Installation on Self-Pope Figure 4

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4? 9. B,7G- (2) Ground the cable shielding and make certain ground lead is properly grounded.

(3) Reconnect all input and output leads. Refer to Sect. 2-2, Fig. 5 or 6, if

necessary for correct wiring.

C. Replace Magnetic Pickup

The magnetic pickup requires critical adjustment when replaced. Refer to Sect.

2-2, Para. 3, B for replacement and adiustment instructions.

See Fig. 5 for magnetic pickup installation on Cummins engines. Installation on

Detroit Diesel engine is shown in Sect. 2-2, Fig. 3.

Magnetic Pickup Installation on Cummins Engines

Figure 5 t

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SECTION 2. ADJUSTMENT

1. General

All of the electric-hydraulic governor system main components, namely the magnetic

pickup, hydraulic actuator, and electric control box, have critical adjustments which

can affect engine performance and therefore, generator output. Actuator-to-fuel con-

trol lever adiustment can also affect engine performance.

When the complete system is to be checked, and/or adjusted, a definite sequence of

procedures should be followed:

First - Check or adiust actuator linkage

Second - Check or adjust magnetic pickup

Third - Check or adjust actuator

Fourth - Check or adjust electric control box

2. Actuator Linkage Adiustment

A. General

The proper adiustment of the mechanical linkage between the hydraulic actuator

and engine speed-control lever is important to the satisfactory operation of other

electric-hydraulic governor components.

One of the most important things to remember about linkage adjustment is that the

actuator and linkage must move the speed control lever through its complete range

of travel, from full idle position to full speed position. An adiustment which does

not provide full travel can cause sluggish operation and poor response time under

load. Also remember to use as much of the actuator lever travel as possible. The

actuator output lever has a maximum travel range of 30 degrees.

B. Adjust Actuator Linkage on Cummins Engines (See Fig. 1)

When adjusting linkage on Cummins engines, remember that the combined weight

of levers (4 and 8, Fig. 1) and rod assembly (7) will automatically hold the linkage

in FULL-SPEED position when the engine is stopped. Check and adjust linkage as

fo I lows:

(1) Assuming that linkage is connected, disconnect and remove rod (7) assembly

by disconnecting ball-ioints (5 and 10) from levers (4 and 8).

(2) Check adjustment and positioning of fuel pump speed control lever (8). The

lever should be positioned on the shaft (9) so that it is pointing toward the

rear of the engine at an angle of about 10 degrees below horizontal when

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the pump shaft (9) is rotated as far as it will go counterclockwise to FULL-SPEED

position (see Fig. 1). Loosen lever clamping screw and reposition lever as re-

quired. Tighten clamping screw securely. Actuate lever to be certain it does not touch any engine parts throughout its full travel range.

(3) Measure the length of rod (7) between adiusting nuts (6). Correct length is

5-l/16 inches. If length, is not within l/16 inch of this dimension, loosen

nuts (6) and adjust.

(4) Connect ball-joint (10) to pump-lever (8) in the threaded hole nearest the ’

end. With both levers (4 and 8) in FULL SPEED position, attempt to connect

the rod assembly to actuator lever (4) in the second mounting hole from the end.

If joint (5) attaching screw will thread easily into the mounting hole the

actuator lever (4), it is properly adjusted on the actuator output shaft (2). If joint screw does not line-up with the mounting hole; loosen clamping bolt

in lever (4) and reposition lever. When repositioning the lever, be sure the

shaft (2) is held in its full speed position (full clockwise rotation). Tighten

lever clamping bolt, and connect rod assembly to lever (4) by installing ball-

joint (5) mounting screw in second mounting hole from end of lever.

REAR FRO NT

View from right

side of engine

(shown in FULL SPEED position)

1. Actuator 6. Nut

2. Actuator output shaft 7. Rod

3. 12-V input terminals 8. Fuel pump lever

4. Actuator lever 9. Fuel pump shaft

5. Ball-joint 10. Ball-joint

2-2

Actuator Linkage, Cummins Engines

Figure 1 s 1’

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(5) Actuate linkage throughout its entire range. Be sure action is free, and with-

out binding or interference. 6

C. Adjust Actuator Linkage on Detroit Diesel Engines (see Fig. 2)

When the engine is stopped, this linkage is normally in IDLE SPEED position. Check

and adjust I inkage.

(1) Disconnect ball joint (2, Fig. 2) from actuator lever (1).

(2) A spring in the speed limiting governor will hold the speed-control lever (5)

in full IDLE position. In this position it should point almost straight outward

at an angle of approximately 10 degrees toward the rear of the engine.

(3)

(4

(5) Move lever (1) to FULL SPEED position (toward the radiator) and make certain

that the linkage will operate the speed control lever freely throughout its full

travel from IDLE to FULL SPEED positions.

(6) Be sure all linkage attaching parts are securely tightened.

Move the actuator lever (1) toward the rear of the engine. In full IDLE position

it should be pointing almost straight upward at an angle of about 10 degrees

toward the rear of the engine (see Fig. 2). If lever (1) requires adjustment,

loosen the lever clamping screw. Rotate the actuator output shaft (12) in a

clockwise direction to full IDLE position and reposition the lever (1) as required.

Tighten lever clamping screw.

With speed control lever (5) and actuator lever (1) both in full IDLE position,

attempt to connect ball joint (2) to lever (1). If ball joint mounting screw

and threaded mounting hole in the lever do not line-up, loosen nuts (7) and

adjust length of rod (4) so that the ball joint may be attached to lever (1)

when both levers are in full IDLE position.

3. Magnetic Pickup Adjustment

A. General

The strength of the magnetic pickup signal to the control box can be weakened if

the tip of the pickup is too far from the flywheel ring gear. If the pickup is to be

removed for any reason, or if the signal is weak, as indicated by test (see 3-2,

Fig. l), the pickup must be adjusted-.

B. Adjustment Procedures

Magnetic pickup adiustment procedures are the same for all installations. Refer

to Fig. 3.

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REAR

Viewed from left

side of engine

1. Actuator lever 2. Ball joint

3. Fuel shut-off lever

4. Rod

5. Speed control lever

6. Ball joint

7. Locknuts

8. Fuel pressure line

9. Terminal

10. Terminal

11. Actuator

12. Actuator output shaft

Actuator Linkage, Detroit Diesel Engines

Figure 2

(1) Disconnect “Amphenol” connector (1, Fig. 3).

(2) Loosen nut (3) and remove magnetic pickup (2).

(3) Inspect to make certain the tip is not damaged from contact with the ring

gear teeth (replace pickup if damaged).

(4) Rotate the engine as required to locate a ring gear tooth directly below the

tapped, pickup mounting hole. An i,maginary line should pass through the center of the mounting hole, the center of a flywheel tooth and the center

of the flywheel.

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Install the magnetic pickup and thread into the mounting hole until the tip

touches the “in line” flywheel-gear tooth . .

CAUTION: THE PICKUP TIP MUST BE DIRECTLY OVER A TOOTH AND

NOT BETWEENTEETH WHEN ADJUSTMENT IS MADE.

Back the pickup outward (counterclockwise) l/2 turn. Hold the pickup securely

in this position and tighten nut (3). This adjustment will result in a clearance

of approximately 0.028 inch between the pickup tip and the flywheel teeth and

give an operating AC voltage of 4 V to 8 V at the control box terminals 5 and

6, when the engine is running at no load and governed speed.

Connect “Amphenol” connector (1).

-.

. “.

1. Connector

2. Magnetic pickup

3. Nut

Magnetic Pickup

Figure 3 t

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4. Hydraulic Actuator Adjustment

A. General

This operation is designed to confine all testing and adiusting to the actuator alone,

and to eliminate the influence of any governor problems outside the actuator. The

operation actually becomes a simulated bench test.

The actuator has one adiustment which determines the voltage values required to

correctly position the output shaft (and lever) throughout its operating range. This

adjustment is controlled by an adiusting screw (3, Fig. 4) located in the bottom

of the actuator body.

8. Adjustment Procedures

To test and adiust the actuator on the engine, proceed as follows:

(1) Start engine and operate at idle speed. With engine-generator controls in IDLE

position, the actuator will be receiving NO signal from the control box.

(2) Note position of actuator leads (black and white) at terminals (1 and 2, Figure

4) so that they may be reconnected properly; then disconnect.

(3) Disconnect ball-joint and rod assembly from actuator lever (see Fig. 1 or 2).

CAUTION: SECURE ENGINE SPEED CONTROL LEVER IN IDLE POSITION.

(4) Make certain the hydraulic pressure (fuel oil) supply to the actuator is adequate

and clean.

NOTE: A restrictor fitting is used in the pressure supply line to the actuator

on all Cummins engines. This fitting is located on the fuel pump

pulsation damper.

(5) Connect a test circuit to actuator as illustrated in Fig. 5. Actuator output

shaft (and lever) should move through its range as potentiometer knob is rotated

and should ,take a given position for each potentiometer setting.

NOTE: If output shaft operates erratically, the trouble is in the hydraulic

supply or the actuator.

(6) Set potentiometer of test circuit so that 1 .5 * 0.2 V DC is supplied to input

terminals of actuator. The actuator shaft and lever should just move off minimum

fuel (idle) position at this voltage. If shaft has not moved off minimum, loosen

locknut (4, Fig. 4) and turn adiusting screw (3) OUT until output shaft does

just leave minimum position. Tighten locknut. .

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“0 P HOBART BROTHERS COMPANY

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1. Dxitive terminal 4. Locknut

2. Negative terminal 5. Pilot valve bushing

3. Pdiusting screw 6. Actuator

Hydraulic Actuator Adiustment

Figure 4

-I- .. 25 OHh’l

12 V.D-C

SUPPLY

POTENTIOMETER POTENTIOMETER

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TO ACTUATOR TO ACTUATOR

TERK’INALS TERK’INALS

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Actuator Test Circuit

Figure 5 t

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NOTE: (a) Use a 5/32-inch Allen wrench to turn the socket-head adjusting

screw (3).

(b) Prevent the actuator pilot valve bushing (5) from turning while

loosening or tightening nut (4), or adjusting screw (3), by placing

an open-end wrench across flats on the bushing.

If at the above input voltage the output shaft has rotated more than 5 degrees

off minimum position, loosen locknut and turn adjusting screw IN until output

shaft moves to just off minimum fuel position. Tighten locknut.

(7) Disconnect test circuit and connect actuator input leads.

(8) Reconnect actuator linkage.

(9) To test, operate the engine at normal governed speed (400 Hz, indicated on

frequency meter). Connect a voltmeter to actuator input terminals (1 and 2,

Fig. 4). If the actuator and linkage are properly adiusted, the voltmeter

should indicate a voltage of 2-V to 4-V DC on the 12-V DC scale.

5. Electric Control Box Adiustment

A. General

Before making an’ adjustment to the control box, make certain the linkage between

the actuator and fuel control lever is free and that there is no backlash, “play”, or

lost mot ion in the linkage. Be sure the magnetic pickup is producing a strong, normal

output. Be sure adequate fuel oil pressure is reaching the actuator and that the

actuator is properly adjusted. The actuator servo piston must be free and not stick-

ing. Adjust control box 8s follows:

B. Adiustment Procedures

(1) Start engine and allow it to warm.

(2) Accelerate engine to governed speed. (See Generator Set Manual .)

(3) Use the adjusting screw in the speed-setting potentiometer (Fig. 6 or 7) to

adjust engine speed to produce a generator output of exactly 400 Hz.

NOTE: (a) A very small screwdriver is required for this adjustment. Turn the

screw CLOCKWISE to INCREASE engine speed, and COUNTER-

CLOCKWISE to DECREASE speed.

(b) This is a 24-turn potentiometer with no stops. The adjusting screw

is designed to slip when the wiper reaches the end of its travel

in either direction. t

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‘i-

Ill-

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To 12-v DC! SolEce

Speed Adjusting' Potentiometer

Reverse Pohr

Electric Control Box and Potentiometer (Original, Old Type) Figure 6 t

2-2

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rOBART D s 0 “0 QQ

iMOTOR GENERATOR DIVISION * 2 HOBRAT BROiHERS COMPANY

a . B @+

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I HORA RT BROTHERS NO. 389870 I

C.W. - Increase

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TO TO

Hydraulic. Actuator r Magnetic Pickup

Shielding Ground

C.C.W. - Decrease

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Electric Control Box and Potentiometer (New Fail-Safe Type)

Figure 7 t

Feb 28/73

a. _- -_s .f

FOBART

I a QQ

EMOTOR GENERATOR DIVISION

“c 2 HOBART BROTHERS COMPANY

% Q. @LO 6

(4) With the engine running smoothly at governed speed (400 Hz), manually force

the actuator lever to an “under-speed” position momentarily to simulate a

sudden loaded condition. The actuator should act immediately to bring the

engine up to governed speed without surging. If actuator action is slow or if

surging is present, adjust the “gain” and “reset-droop” potentiometers per

steps (5) and (6).

(5) Loosen locknuts on “gain” and “reset ‘droop” adjusting screws. Set both adjust-

ing screws at midrange (no. 5 on the scale). Turn the “gain” adjusting screw

slowly clockwise until engine operation becomes slightly unstable (surges).

NOTE: It may be necessary to manually force the actuator lever to an

underspeed position momentarily to initiate surging.

(6) -Adjust “reset-droop” to stabilize engine speed. (Screw rotation requirement,

CLOCKWISE or COUNTERCLOCKWISE, cannot be predetermined .) Again,

turn the “gain”

unstable.

adiustment screw CLOCKWISE until the engine becomes slightly

Stabilize with “reset” adjustment. Repeat steps (5) and (6) until the

reset potentiometer will no longer stabilize engine operation. Turn the gain

adiusting screw back to its last position and stabilize.

NOTE: Although best performance is obtained with the “gain” setting as high

as possible (clockwise) while the engine is still stable, it is not ad-

visable to adjust the “gain” too high because an excessively “high”

or-delicate adiustment will very likely result in unstable (surging)

operation when the unit is not thoroughly warmed. Adiust gain and

reset droop to maximum while still attaining stability. Then back

off both settings by 2 digits. For example, scale settings of 8 and 6

should be backed off to 6 and 4.

(7) Tighten locknuts when adjustment is completed.

t

Feb 28/73 7’

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Feb 28/73 ,-- I/ -,. i' z .:- _

HOBART e 5

QD

$MOTOR GENERATOR DIVISION

> i HOBART EROTHEAS COMPANY 9 4. BLTt5+

1. General

2.

CHAPTER 3. TROUBLE SHOOTING

SECTION 1. T.HEORY OF OPERATION

The electric-hydraulic governor system is primarily an electrical installation. The only

-hydraulic function performed is actuation of the mechanical fuel control linkage through

a piston and lever arrangement in the actuator. Engine fuel pressure supplies the re-

quired hydraulic power.

The system consists of four principal components which are illustrated schematically on

diagrams which accompany the Generator Set Manual. Components are identified on

schematics as: “electric governor control box”, “magnetic pickup”, “actuator”, and

“2RH” which is the speed setting potentiometer.

The electronic circuitry of the control box will not, and need not, ‘be discussed in the

theory of operation. Operators and, maintenance .personnel should concern themselves

only with signals which enter and leave the contrdl box. Servicewise the control box

should be considered as an adjustable and replaceable module and should be serviced as

such.

Basic Theory of Operation

Electrical operating power is supplied to the control box from the 12-V DC engine system

through variqus switching and relay circuits depending upon the end item (self-propelled,

tractor mounted, etc.) requirements. Input power (12-V DC) enters the box through

terminal No. 1, however on some of the original old style boxes it is routed by way of

terminal No. 8, which is not internally connected. This method is used mainly to pto-

vide convenient mounting and connection for a diode (4REC), which is used to prevent

accidental entrance of reverse polarity into the solid state circuitry of the control box.

New type “fail-safe” control boxes are equipped with an internally mounted diode,

therefore input power is connected directly’ to terminal No. 1 on these boxes. The con-

trol box receives two signals; one from the potentiometer (2RH), and one from the MAG-

NETIC PICKUP. The control box sends a signal to the ACTUATOR.

The voltage value of the input signal from the potentiometer (2RH) determines the

governed speed of the engine. The potentiometer signal enters the box through terminals

9 (+) and 10 (-) . Th e value of this signal may be varied from 0 V DC (minimum engine

speed) to 1.5 V DC ( maximum engine speed). Voltage (and engine speed) is increased

by turning the “pot” adjusting screw CLOCKWISE. It is decreased by turning the screw

COUNTERCLOCKWISE (Ref. Sect. 2-2; Figs. 6 and 7). Twenty-four complete turns

(revolutions) of the screw are required to move the adiusting slide from minimum to

maxiumum speed setting. There are no stops, as such, on this potentiometer; however

the adjusting screw will “slip” to prevent damage to internal parts when the slide reaches

Feb 28/73 x..._ J j I:.+~ rnL ‘ _,

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HOBART

e z

QD

;MOTOR GENERATOR DIVISION

“c 2 HOBART BROTHERS COMPANY %. &..,l@+

either end of its travel. In schematic diagram (Figure 2) the potentiometer adiusting

slide is shown in maximum voltage (and speed) position. The potentiometer signal is

amplified after it enters the control box and becomes the speed setting signal voltage.

The other signal which enters the control box is an AC signal from the magnetic pickup,

which is a device for sensing the speed of the engine. The pickup is mounted in the

flywheel housing, with the tip (magnetic field end) very close to the starter ring gear.

The device will produce a voltage output when any magnetic material moves through

its. magnetic fie Id. Thus, as each tooth on the ring gear passes through the magnetic

field, an electric pulse is sent to the control box.

Inside the box these pulses are converted to DC voltage proportional to engine speed.

An increase in engine speed results in an increased voltage, and conversely a decrease

in engine speed results in a decrease in voltage. The DC voltage converted from the

pulsing signal out of the magnetic pickup becomes the speed signal in the control box.

In operation, the speed signal voltage is compared to the speed setting signal voltage

as adjusted by the potentiometer (2RH). The difference between these signals deter-

mines the value of the output signal voltage to the actuator.

The hydraulic actuator is a proportional type, that is, its output shaft takes an angular

position proportional to a given input signal voltage. As stated above, the actuator is

electrically controlled and is hydraulically powered by fuel oil pressure. It has no

rev0 lving parts. (See Figure 1.) A pilot valve controls flow of oil to (or from) a servo

piston which is connected by an internal lever to an output shaft. Actuator power is

transmitted from the actuator output shaft to the engine speed control arm through a

lever and adjustable rod mechanism. As the pilot valve moves downward, oil is admitted

under the servo piston to push it up and increase engine speed. When the pilot valve

moves upward, oil is released from beneath the piston, allowing it to move downward

and reduce engine speed.

The actuator pilot valve is attached to a permanent magnet in a transducer. The output

signal from the control box passes through the transducer coil and tends to push the mag-

net and pilot valve plunger downward. A feedback spring and a top centering spring add

to this downward force. A bottom centering spring resists the downward push. When the

engine is running “on speed”, these opposing forces are equal and the pilot valve is

centered so that no oil flows to, or from, the actuator servo to change the position of

the output shaft. A change in the voltage signal from the control box results in a

change in the pilot valve position. The resulting oil flow to (or from) the servo pro-

duces a change in the output shaft to either increase or decrease engine speed. For

each input signal voltage from the control box, there is but one position of the output

shaft at which the bottom centering spring force exactly opposes the force in the trans-

ducer coil and the top springs when the pilot valve is centered.

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Feb 28/73

GENERATOR DIVISION nOBART BROTHERS COMPANY

Feedbtlck-" Spring

1 h \ \ \

El.01 Valve 3~ shing,

Actuator Goss-Section

Figure 1 I

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!OBART D a QD

iMOTOR GENERATOR DIVISION

% 2 HOBART BROTHERS COMPANY

‘CF 0. BL&

During an underspeed condition, when engine speed is below the speed selected by the

potentiometer, the control box output voltage to the actuator is at maximum (as high as

8 to 10 V DC), to force the magnet and pilot valve down and allow the actuator piston

and output shaft to move to maximum fuel position. During an overspeed cord ition

when engine speed exceeds the set speed, the control box output voltage will be zero

and the actuator will move to minimum fuel position.

At no-load, the governor will control engine speed with a control boxoutput (actuator

input) of 2 V to 4 V DC. At full load, the voltage will be 0.5 V to 1 .O V DC higher

than no load value. Response time and stability of the system are adjustable by two

potentiometers identified as “GAIN” and “RESET-DROOP” controls on the electric

control box (Sect. 2-2, Figs. 5 and 6). Adjustment of these controls is covered in

Section 2-2, Para. 5, B, (5) and (6). Electric governor voltage values are contained

in Section 3-2, Fig. 1.

/-

ELECTRIC

CO NTRO L BOX

TERMINALS

SLIDE DIRECTION - ADJUSTING SCREW ROTATION

SLIDE SHOWN AT - CW - INCREASE VOLTAGE

MAXIMUM VOLTAGE AND ENGINE SPEED.

AND ENGINE SPEED

POSITION - CCW - DECREASE VOLTAGE

AND ENGINE SPEED.

/

.

Speed Setting Potentiometer Schematic

Figure 2

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Feb 28/73

II” I:: i

HOBART z 6 QD

$MOTOR GENERATOR DIVISION

“0 i HOBART BROTHERS COMPANY

% 4. B,+e

.

SECTION 2. TROUBLE SHOOTING PROCEDURES

1. General

Trouble shooting is an orderly process of checking and eliminating possible causes of

trouble until the exact cause of a trouble is found. As a rule, the best place to start

looking for the cause of a trouble in a circuit is at the source of power. Continue test-

ing and checking the circuit, step-by-step, in an orderly manner, until the cause of

trouble is located. See applicable connection diagrams and schematic diagrams which

are furnished with the generator set or governor “kit”.

2. Trouble Shooting Chart

A. Description

The trouble shooting charts lists information under three headings:

(1) Trouble, symptom, and condition

(2) Probable cause

(3) Test, check, and remedy

B. Use of the Trouble Shooting Chart

Read the trouble symptoms and conditions before proceeding to causes and remedies.

For example, at the beginning of the trouble shooting chart, the first trouble listed

is: “Engine will not come up to governed speed”. If the engine does come up to

speed, then obviously this is not your symptom and condition. Proceed to the next

trouble and symptom directly below. When the applicable trouble symptom and

condition has been found, look to the right under PROBABLE CAUSE and TEST,

CHECK, AND REMEDY to find the various things which could cause the trouble

and what to do to check and correct them.

3. Equipment for Trouble Shooting

A good quality multi-scale voltohmmeter is the only instrument required for trouble

shooting. At least two “jumper” leads with “alligator”, or similar clips, may be

required. The 12-V, engine electrical system is used for the 12-V DC power source.

4. Safety

WARNING: EXERCISE EXTREME CARE TO AVOID CONTACT WITH HIGH VOLTAGE

LEADS AND COMPONENTS WHICH COULD CAUSE SERIOUS SHOCK

AND INJURY IF TOUCHED WHEN TROUBLE SHOOTING OR OPERAT-

ING ANY EQUIPMENT.

I

Feb 28/73 .-,- .[_ -~(,‘g

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HOBART

: t

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iMOTOR GENERATOR DIVISION

,= HOBART BROTHERS COMPANY “c 5 . B ,+*

5. Connections and Leads

ALWAYS make a check of connections and leads to a component suspected of being

faulty. With the exception of a few instances, we wil I assume that connections and

wiring have always been checked first and that power has not been lost as a result of

defective wiring or connections.

6. Trouble Shooting Guides

The following facts concerning the operation of the electric-hydraulic governor may be

helpful in understanding the system and in determining which unit in the system is

faulty in case of troubles.

A. The system requires three sources of power to operate normally.

(1) 12-V DC input power (from engine circuit).

(2) Approximately 4-V to 6-V AC input power (from magnetic pickup).

(3) 20 psi, or more, pressure (from engine fuel oil system).

NOTE: Low pressure will result in sluggish actuator operation.

B. Assuming other conditions are normal, the actuator will go to, or remain in,

CLOSED THROTTLE position under the following conditions:

(1) No 12-V DC po wer from engine electrical system.

(2) No voltage from control box to actuator.

C. Also assuming other conditions are normal, the actuator will go to FULL THROTTLE

position under the following condition:

(1) No signal (AC po wer ) f tom the magnetic pickup to the control box. (Applies

to all boxes except “fail-safe” (see 2-2, Fig. 7.)

D. The actuator will “surge” or “hunt” under the following conditions:

(1) “Rate” or “gain” potentiometers improperly adjusted.

(2) Actuator linkage to governor throttle,. loose.

(3) Throttle linkage binding.

(4) bw fuel pressure at actuator.

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FOBART D ii gMOTOR GENERATOR DIVISION n “c

QD d HOBART BROTHERS COMPANY

% Q.BLO ‘+

(5) Dirty actuator.

(6) Weak signal from magnetic pickup.

E. Electric governor voltage values are listed in Figure 1.

-

L

Terminal #8 (Input, anytime switch is ON) (approx.)

Terminal #9 (apptox.) to -

Terminals #9 to #lo (approx.)

Terminals #3 to #4 (on speed, no load)

(Input’to actuator)

Terminals #3 to #4 (on speed, full load)

12. V DC

8. to 10. V DC

1.5 V DC

2. to 4. V DC

0.5Vto l.OVDC

HIGHER than NO

LOAD value.

Terminals #5 to #6 (Magnetic pickup input

at box; leads connected, idle speed)

NOTE: 1. Some early production boxes have an input

rating of 0.5 V AC minimum.

2. V AC minimum

2. Values will increase with increased engine speed.

Magnetic pickup output. (Leads disconnected from

box. All models. Idle speed.) 6. V AC minimum

WARNING: NEVER DISCONNECT MAGNETIC PICKUP LEADS WHEN THE

ENGINE IS RUNNING AT GOVERNED SPEED.

Feb 28/73 .“.-e. ~.’ .>, .A / 1‘

Electric Governor Voltage Values

Figure 1

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YOBARI

t QD EMOTOR GENERATOR DIVISION

z : HOBART BROTHERS COMPANY “0 e b . B ,, I++

‘ROUBLE,SYMPTOM,

4ND CO ND IT IONS PROBABLE CAUSE TEST, CHECK, AND/OR REMEDY

! . Engine overspeeds B. Actuator linkage binding B. Check linkage and adjust as re-

(Continued) or improperly adjusted. quired.

C. Defective or sticking C. Clean or replace as required.

actuator.

3. Engine “surges” . A. Actuator linkage loose, A. Check and adjust linkage in

or binding. accordance with Sect. 2-2; Para.

2, Bor C.

B. Electric control box im- B. Adiust in accordance with Sect.

properly adjusted. 2-2; Para. 5, B.

Feb 28/73

1 -(’ ,-- <

Trouble Shooting Chart (Sheet 2 of 2)

Figure 2 3-2

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HOBART 8 z QQ EMOTOR GENERATOR DIVISION

5 “0 2

HOBART BROTHERS COMPANY

% *. BLTl B

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