Hobart Brothers 90 GT 20 Setup guide

OM-2028
010187
Revised 042393
Revised 071596
OPERATION AND MAINTENANCE
MANUAL
with
ILLUSTRATED PARTS LIST
for
ENGINE-DRIVEN GENERATOR SET
Series Numbers 6910, 6910A, 6910B, 6910C
MODEL90GT20
90-KVA, 400-HZ, 115/200-V AC, 3-PHASE
Specification Number Mounting Voltage Regulator Used
6910-1, 6910A-1, 6910B-1 Trailer or Truck 430391C
6910C-1
6910A-2, 6910B-2, 6910C-2 Trailer or Truck 489812A
6910A-3, 6910B-3, 6910C-3 Fixed Unit W/Fuel
Tank & Batteries 489812A
6910B-4, 6910C-4 4-Wheel trailer, 5th Wheel
Trailer, or Truck 489812A
6910B-5, 6910C-5 Tractor 489812A
Hobart Brothers Company
Airport Systems Group
Ground Power Equipment
Troy, Ohio 45373
U.S.A.

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SAFETY INSTRUCTIONS AND WARNINGS FOR ELECTRICAL POWER EQUIPMENT
WARNING
ELECTRIC SHOCK can KILL. Do not touch live electrical parts.
ELECTRIC ARC FLASH can injure eyes, burn skin, cause equipment damage, and ignite combustible
material. DO NOT use power cables to break load and prevent tools from causing short circuits.
IMPROPER PHASE CONNECTION, PARALLELING, OR USE can damage this and attached
equipment.
Important:- Protect all operating personnel. Read, understand, and follow all instructions in
the Operating/Instruction Manual before installing, operating, or servicing the equipment. Keep
the manual available for future use by all operators.
A. GENERAL
Equipment that supplies electrical power can cause serious injury or death, or damage to other equipment
or property. The operator must strictly observe all safety rules and take precautionary actions. Safe practices
have been developed from past experience in the use of power source equipment. While certain practices be-
low apply only to electrically-powered equipment, other practices apply to engine-driven equipment, and some
practices to both.
B. SHOCK PREVENTION
Bare conductors, or terminals in the output circuit, or ungrounded, electrically-live equipment can fatally
shock a person. Have a certified electrician verify that the equipment is adequately grounded and learn what
terminals and parts are electrically HOT. Avoid hot spots on machine. Use proper safety clothing, procedures,
and test equipment.
The electrical resistance of the body is decreased when wet, permitting dangerous currents to flow
through it. When inspecting or servicing equipment, do not work in damp areas. Stand on a dry rubber mat
or dry wood, use insulating gloves when dampness or sweat cannot be avoided. Keep clothing dry, and
never work alone
1. Installation and Grounding of Electrically Powered Equipment
Equipment driven by electric motors (rather than by diesel or gasoline engines) must be installed and
maintained in accordance with the National Electrical Code, ANSI/NFPA 70, or other applicable codes. A
power disconnect switch or circuit breaker must be located at the equipment. Check the nameplate for volt-
age, frequency, and phase requirements. If only 3-phase power is available, connect any single-phase rated
equipment to only two wires of the 3-phase line. DO NOT CONNECT the equipment grounding conductor
(lead) to the third live wire of the 3-phase line, as this makes the equipment frame electrically HOT, which can
cause a fatal shock.
Always connect the grounding lead, if supplied in a power line cable, to the grounded switch box or build-
ing ground. If not provided, use a separate grounding lead. Ensure that the current (amperage) capacity of
the grounding lead will be adequate for the worst fault current situation. Refer to the National Electrical Code
ANSI/NFPA 70 for details. Do not remove plug ground prongs. Use correctly mating receptacles.
2. Output Cables and Terminals
Inspect cables frequently for damage to the insulation and the connectors. Replace or repair cracked or
worn cables immediately. Do not overload cables. Do not touch output terminal while equipment is energized.
3. Service and Maintenance
This equipment must be maintained in good electrical and mechanical condition to avoid hazards stem-
ming from disrepair. Report any equipment defect or safety hazard to the supervisor and discontinue use of
the equipment until its safety has been assured. Repairs should be made by qualified personnel only.
Before inspecting or servicing electrically-powered equipment, take the following precautions:

a. Shut OFF all power at the disconnecting switch or line breaker before inspecting or servicing the
equipment.
b. Lock switch OPEN (or remove line fuses) so that power cannot be turned on accidentally.
c. Disconnect power to equipment if it is out of service.
d. If troubleshooting must be done with the unit energized, have another person present who is trained in
turning off the equipment and providing or calling for first aid.
C . FIRE AND EXPLOSION PREVENTION
Fire and explosion are caused by electrical short circuits, combustible material near engine exhaust pip-
ing, misuse of batteries and fuel, or unsafe operating or fueling conditions.
1. Electrical Short Circuits and Overloads
Overloaded or shorted equipment can become hot enough to cause fires by self destruction or by causing
nearby combustibles to ignite. For electrically-powered equipment, provide primary input protection to remove
short circuited or heavily overloaded equipment from the line.
2. Batteries
Batteries may explode and/or give off flammable hydrogen gas. Acid and arcing from a ruptured battery
can cause fires and additional failures. When servicing,do not smoke, cause sparking, or use open flame
near the battery.
3. Engine Fuel
Use only approved fuel container or fueling system. Fires and explosions can occur if the fuel tank is not
grounded prior to or during fuel transfer. Shut unit DOWN before removing fuel tank cap. DO NOT com-
pletely fill tank, because heat from the equipment may cause fuel expansion overflow. Remove all spilled fuel
IMMEDIATELY, including any that penetrates the unit. After clean-up, open equipment doors and blow fumes
away with compressed air.
D. TOXIC FUME PREVENTION
Carbon monoxide - Engine exhaust fumes can kill and cause health problems. Pipe or vent the exhaust
fumes to a suitable exhaust duct or outdoors. Never locate engine exhausts near intake ducts of air condition-
ers.
E. BODILY INJURY PREVENTION
Serious injury can result from contact with fans inside some equipment. Shut DOWN such equipment for
inspection and routine maintenance. When equipment is in operation, use extreme care in doing necessary
trouble-shooting and adjustment. Do not remove guards while equipment is operating.
F. MEDICAL AND FIRST AID TREATMENT
First aid facilities and a qualified first aid person should be available for each shift for immediate treat-
ment of all injury victims. Electric shock victims should be checked by a physician and taken to a hospital im-
mediately if any abnormal signs are observed.
EMERGENCY FIRST AID
Call physician immediately. Seek additional assistance. Use First Aid techniques recommended
by American Red Cross until medical help arrives.
IF BREATHING IS DIFFICULT, give oxygen, if available, and have victim lie down. FOR ELECTRI-
CAL SHOCK, turn off power. Remove victim; if not breathing, begin artificial respiration, preferably
mouth-to-mouth. If no detectable pulse, begin external heart massage. CALL EMERGENCY RESCUE
SQUAD IMMEDIATELY.
G. EQUIPMENT PRECAUTIONARY LABELS
Inspect all precautionary labels on the equipment monthly. Order and inspect all labels that cannot be
easily read.

LIST OF EFFECTIVE PAGES
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Table of Contents
SUBJECT CHAPTER/SECTION PAGE
WARNING
LIST OF EFFECTIVE PAGES
INTRODUCTION
CHAPTER 1. DESCRIPTION/OPERATION
SECTION1.DESCRIPTION..........1-1.........1
1.General.................... 1-1...........1
2.Orientation.................. 1-1...........1
3.SpecialFeatures............... 1-1...........1
A.ProtectiveMonitor .................1-1............. 3
B.Pull-outTrays ...................1-1............. 3
C.VoltageRegulator .................1-1............. 3
D.TestCircuitry....................1-1............. 3
E.ElectricGovernor .................1-1............. 3
F.LowFuelLevelShutdownSwitch.........1-1............. 3
4.Identification................. 1-1...........5
A.General.......................1-1............. 5
5.OptionalEquipment............. 1-1...........6
A.Trailer........................1-1............. 6
B.Transformer-Rectifier ...............1-1............. 6
C.Truck ........................1-1............. 6
D.SecondOutputandControlBox .........1-1............. 6
E.QuickStartKit ...................1-1............. 6
F.MemoryandTimeDelayBoard..........1-1............. 6
6.Canopy.................... 1-1...........6
7. Engine, Generator, and Controls
Assembly .................... 1-1...........7
A.BasicEngine....................1-1............. 7
B.EngineManufacturer’sEquipment........1-1............. 7
C.HobartEngineEquipment ............1-1............. 7
(1)Electricgovernorsystem ............1-1............. 7
(a) Magnetic pickup 1-1 7
(b) Control unit 1-1 9
(c) Actuator 1-1 9
(2) Engine electrical system 1-1 9
(3) Engine protective devices 1-1 9
(4) Air cleaner 1-1 9
(5) Exhaust system 1-1 9
(6) Radiator 1-1 11
D.Generator .....................1-1.............11
May 1/91 Revised Table of Contents
Page 1
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SUBJECT CHAPTER/SECTION PAGE
E.ControlBoxAssembly.............. 1-1.............12
(1) Generator control tray 1-1 13
(a) Resistors 1-1 13
(b) Generator output monitors (meters) 1-1 13
(c) Meter and line switches 1-1 13
(d) Receptacle connector 1-1 13
(e) Tray 1-1 13
(f) Manual voltage control 1-1 13
(g) Excitation-deenergization relay 1-1 13
(2) Protective relay tray 1-1 15
(a) Sensing modules 1-1 15
(b) Memory and time delay module 1-1 15
(c) Indicating lights 1-1 16
(d) Plug-interlock relay 1-1 16
(e) Test-bank switch 1-1 16
(f) Resistor 1-1 16
(g) Fuse-interlock relay 1-1 16
(h) Connector 1-1 16
(k) Auxiliary underfrequency relay 1-1 16
F.EngineControlPanel............... 1-1.............18
(1) Engine instruments 1-1 18
(2) Engine and generator controls 1-1 18
(3) Air cleaner indicator 1-1 19
(4) Test receptacle connector 1-1 20
G. Power Module Panel Assembly ......... 1-1.............21
(1) Load contactor 1-1 21
(2) Current transformers 1-1 21
(3) Overload module 1-1 22
(4) Rectifier 1-1 22
(5) Terminal boards 1-1 22
8.TestBox....................1-1 ..........24
A.Description .................... 1-1.............24
B.TheoryofOperation ............... 1-1.............24
9.WaterHeaterKit ...............1-1 ..........25
SECTION 2. PREPARATION FOR USE,
STORAGE, OR SHIPPING .......... 1-2.........1
1.PreparationforUse..............1-2 .......... 1
A.General ...................... 1-2.............1
B.Inspection/Check................. 1-2.............1
C.InstallingOutputCables............. 1-2.............2
(1) Three-phase, AC output cable assembly
installation 1-2 2
(2) Transformer-Rectifier (DC) output cable
installation 1-2 3
TableofContents May1/91Revised
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SUBJECT CHAPTER/SECTION PAGE
2.PreparationforStorage........... 1-2...........3
A.General.......................1-2............. 3
B.TemporaryStorage ................1-2............. 3
C.LongTimeStorage(Over30Days) .......1-2............. 4
SECTION3.OPERATION...........1-3.........1
1.General .................... 1-3...........1
2.OperatingtheGeneratorSet ........ 1-3...........1
A.Pre-startInspection ................1-3............. 1
B. Normal Engine Starting Procedures .......1-3............. 1
C.ColdWeatherEngineStartingProcedures ...1-3............. 4
D. Preparation for Power Delivery
(AutomaticVoltageControl) ..........1-3............. 6
E.PowerDelivery(AutomaticVoltageControl)...1-3............. 5
F. Preparation for Power Delivery
(ManualVoltageControl) ............1-3............. 6
G.PowerDelivery(ManualVoltageControl) ....1-3............. 7
H.DiscontinuePowerDelivery............1-3............. 7
K.StoppingtheEngine ...............1-3............. 7
3.TestBoxOperation ............. 1-3...........7
4. Transformer-Rectifier Operation . . . . . . 1-3 . . . . . . . . . . . 9
A.DirectCurrentPowerDelivery ..........1-3............. 9
B. Simultaneous 28.5-V DC and 115-V AC
PowerDelivery ....................1-3............. 9
5.TrailerOperation(Optional)......... 1-3.......... 10
A.Towing .......................1-3.............10
B.Parking.......................1-3............. 10
CHAPTER 2. SERVICE
SECTION 1. MAINTENANCE .........2-1.........1
1.General.................... 2-1...........1
2.Inspection .................. 2-1...........1
3.Lubrication.................. 2-1...........1
A.General.......................2-1............. 1
B.Generator .....................2-1............. 1
C.GeneratorControls ................2-1............. 1
D.Engine .......................2-1............. 1
(1) Lubrication schedule 2-1 2
(2) Oil specification 2-1 2
(3) Oil viscosity 2-1 2
(4) Changing engine oil 2-1 2
(5) Changing engine oil filter 2-1 2
E.Starter .......................2-1............. 2
August 31/90 Revised Table of Contents
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SUBJECT CHAPTER/SECTION PAGE
4.AirCleanerService..............2-1 ..........3
A.AirCleanerwithReplaceableFilter....... 2-1............. 3
(1) Cartridge Removal 2-1 3
(2) Cartridge Installation 2-1 4
B.DisposableAirCleaner.............. 2-1.............4
(1) Inspecting the Air Cleaner 2-1 4
(2) Cleaning Instructions 2-1 5
C.Disposal...................... 2-1.............5
5.EngineFuel ..................2-1 .......... 5
A.Quality ...................... 2-1.............5
B.FuelFilter..................... 2-1.............5
6.EngineCoolingSystem............2-1 .......... 5
A.General ...................... 2-1.............5
B.RadiatorCap ................... 2-1.............6
(1) General 2-1 6
(2) Removal 2-1 6
(3) Installation 2-1 6
C.WarmWeatherOperation ............ 2-1.............6
D.ColdWeatherOperation............. 2-1.............6
(1) General 2-1 6
(2) Checking coolant solution 2-1 6
(3) Preparing the coolant solution 2-1 7
(4) Installing the antifreeze solution 2-1 7
E.DrainingtheCoolingSystem .......... 2-1.............7
F.CleaningtheCoolingSystem .......... 2-1.............8
G.CleaningtheRadiatorCore ........... 2-1.............8
H.FillingtheCoolingSystem ........... 2-1.............8
7.GeneratorMaintenance ...........2-1 ..........8
A.Cleaning ..................... 2-1.............9
B.Adjustment .................... 2-1.............9
8.DriveBelts ..................2-1 .......... 9
A.CheckingBeltTension ............. 2-1.............9
B.BeltAdjustment ................. 2-1.............9
9. Trailer, Truck and Battery Maintenance . . . 2-1 . . . . . . . . . . 9
10.ServiceHelps ................2-1 ..........9
A.Wiring....................... 2-1.............9
B.ControlBoxTrays ................ 2-1.............10
C.GeneratorExciter ................ 2-1.............10
D.EngineControlPanel .............. 2-1.............11
SECTION2.INSPECTION/CHECK ..... 2-2.........1
1.General ....................2-2 ..........1
2.Engine.....................2-2 ..........1
A.Fuel ........................ 2-2.............1
B.Lubrication .................... 2-2.............1
C.Coolant ...................... 2-2.............1
D.V-Belts....................... 2-2.............1
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SUBJECT CHAPTER/SECTION PAGE
E.ExhaustSystem..................2-2............. 1
3.ElectricalSystem(12-VDC)......... 2-2...........3
A.Lights .......................2-2............. 3
B.Fuses........................2-2............. 3
C.WiringandConnections .............2-2............. 3
4. Electrical System (115-V AC) . . . . . . . 2-2 . . . . . . . . . . . 4
A.MonitoringInstruments..............2-2............. 4
B.IndicatingLights .................2-2............. 4
C.ProtectiveModules ................2-2............. 4
D.WiringandConnections .............2-2............. 5
5.TrailerandTruck .............. 2-2...........5
SECTION3.ADJUSTMENT/TEST ......2-3.........1
1.General.................... 2-3...........1
2.GeneratorSetTest.............. 2-3...........1
A.Pre-operationalTestProcedures.........2-3............. 1
B.OperationalTestProcedures...........2-3............. 5
3.GeneratorSetAdjustment ......... 2-3.......... 10
A.GeneratorAdjustment ..............2-3.............10
B.GeneratorControlAdjustments .........2-3.............10
C.BasicEngineAdjustments ............2-3.............10
D.EngineAccessoriesAdjustment .........2-3............. 10
E.ElectricGovernorSystemAdjustment......2-3.............11
(1) Actuator linkage adjustment 2-3 11
(2) Magnetic pickup adjustment 2-3 12
(3) Adjustment and Test of Controller and Actuator 2-3 14
(a) Preliminary Controller Settings 2-3 14
(b) Checking No-Load Operation of
Controller 2-3 14
(c) Checking Operation of Controller
Under Load 2-3 14
(d) Checking the Actuator 2-3 16
(4) Checking Magnetic Pick-up signal 2-3 16
5.GeneratorandExciterTest......... 2-3.......... 16
6.DiodeTest .................. 2-3.......... 17
A.Disconnectdiodelead(s)..............2-3............. 1
CHAPTER 3. TROUBLESHOOTING
SECTION 1. TROUBLE SHOOTING
PROCEDURES .................3-1.........1
1.General.................... 3-1...........1
2.TroubleShootingChart(Figure5) ..... 3-1...........1
3.EquipmentforTroubleshooting ...... 3-1...........2
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SUBJECT CHAPTER/SECTION PAGE
4.Safety .....................3-1 ..........2
5.PartsReplacement ..............3-1 .......... 2
6.TestValues ..................3-1 .......... 3
7.CheckingConnectionsandLeads......3-1 ..........3
8.ElectricGovernorTroubleShooting.....3-1 ..........3
9. Engine Trouble Shooting Procedures . . . . 3-1 . . . . . . . . . . 4
A.General...................... 3-1.............4
10.Illustrations . . . . . . . . . . . . . . . . . . 3-1 . . . . . . . . . .
CHAPTER 4. ILLUSTRATED PARTS LIST
SECTION 1. INTRODUCTION ........ 4-1.........1
1.General ....................4-1 ..........1
2.Purpose ....................4-1 ..........1
3.Arrangement..................4-1 ..........1
4.ExplanationofPartsList...........4-1 .......... 1
A.Contents ..................... 4-1.............1
B.PartsListForm.................. 4-1.............1
SECTION 2. MANUFACTURER’S CODES . 4-2 .........1
1. Explanation of Manufacturer’s
(Vendor)CodeList................4-2 .......... 1
SECTION3.PARTSLIST .......... 4-3.........1
1. Explanation of Parts List Arrangement . . . 4-3 . . . . . . . . . . 1
2.SymbolsandAbbreviations .........4-3 ..........1
CHAPTER 5. OPTIONAL EQUIPMENT
CHAPTER 6. MANUFACTURERS’ LITERATURE
UNUSUAL SERVICE CONDITIONS
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Table of Contents August 31/90 Revised
Page 6

INTRODUCTION
This manual contains operation and maintenance information for a series of 400-Hertz generator sets
manufactured by Hobart Brothers Company, Power Systems Group, Troy, Ohio 45373.
This manual is not intended to be a textbook on electricity or electronics. Its primary purpose is to pro-
vide information and instructions to experienced operators, electricians, and mechanics who have
never seen or operated this equipment. It is the intent of this manual to guide and assist operators
and maintenance people in the proper use and care of the equipment.
Use of the manual should not be put off until a trouble or need for help develops. Read the instruc-
tions before starting the unit. Learn to use the manual and to locate information contained in it. Its
style and arrangement are very similar to commercial aircraft manuals. The manual is divided into six
chapters. Each chapter is divided into as many sections as required. Each new section starts with
page 1. Each page is identified by chapter, section and page number, which are located in the lower,
outside corner. When information located in another portion of the manual is referred to, its location is
identified by a chapter, section, and paragraph, or figure number. For example, “
(See 2-3, Para. B)”
refers to information located in Chapter 2, Section 3, Paragraph B. If a Chapter and Section are not in-
dicated in a reference, the referenced material is located in the same section as the reference, Exam-
ple,
(See Para. B).
In addition to operation and maintenance instructions, the manual contains an illustrated parts list in
Chapter 4, and a collection of manufacturer’s literature and supplemental information in Chapter 6.
Content of the manual is arranged as follows:
Chapter 1. Description/Operation
Chapter 2. Servicing
Chapter 3. Troubleshooting
Chapter 4. Illustrated Parts List
Chapter 5. Optional Equipment
Chapter 6. Manufacturer’s Literature
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Introduction June 20/89 Revised
Page 2

CHAPTER 1. DESCRIPTION/OPERATION
SECTION 1. DESCRIPTION
1. General
Four series of generator sets are covered by this manual: Series 6910, Series 6910A, Series 6910B, and
6910C.
Generator sets in Series 6910A are an improved version of the original Series 6910 generator sets.
Series 6910A generator sets feature armatures with Hoover Bearings, Browning Coupler, and differ-
ent magnetic pole construction for the generator revolving field. This new armature can be easily iden-
tified by the two copper rings on each end of the field coils and copper wedges between the magnetic
poles.
Generator sets in Series 6910B feature the same magnetic pole construction for the generator revolv-
ing field as Series 6910A generator sets. In addition, Series 6810B generator sets also feature wide-
type Fafnir bearings on the generator.
Generator sets in Series 6910C are identical to Generator sets in Series 6910B, except that the en-
gine has an improved fuel pump and a dual speed governing system for adjustment of idle speed and
rated speed.
Within a particular series, the basic generator set - including the engine, generator and all controls - is
identical for all units in the series. However, within a particular series different variations of the basic gen-
erator set are offered. Each variation is identified by a specification number, which is derived by adding a
dash number
(-1, -2, etc.) suffix is to the Series number. The specification number generally indicates the
manner in which the particular individual unit is mounted, (such as trailer mounting, tow tractor mounting,
stationary mounting, truck mounting, etc.) and it may also indicate some other special feature of the unit.
Identification of different specifications within each series will be explained later in the Description.
Information and instructions throughout the manual apply to all specifications. Information which applies
only to a certain specification will be qualified and identified as such.
The purpose of the generator set
(Fig. 1) is to generate and deliver regulated, 400-Hz electrical power to
a parked
(or towed) aircraft for operation of the aircraft’s electrical equipment when the on-board gener-
ators are not running. The engine, generator, and controls are designed into a compact unit. See Figure
2 for specifications and capabilities.
2. Orientation
For purpose of orientation and to familiarize operators and maintenance personnel with the location of
components, the radiator is considered to be at the FRONT of the unit. The generator and controls are at
the REAR.
RIGHT and LEFT are determined by standing at the rear end facing the machine. Thus, the generator
control box, output receptacle connector, and engine control panel are mounted on the LEFT side at the
REAR of the unit.
3. Special Features
The generator set has many special features which are later described more fully under the assemblies in
which they appear. Some of the main features are mentioned here and described briefly.
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1. Canopy 6. Output cable horn
2. Access-vent covers 7. Mounting frame
3. Lifting eye 8. Engine fan exhaust deflectors
4. Windows 9. Engine exhaust pipe
5. Output receptacle cover 10. Radiator cap access cover
Generator Set
Figure 1
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A. Protective Monitor
A single, solid-state device
(4, Fig. 8) receives signals from all of the fault sensing units in the gener-
ator output circuit and functions to cause the load to be disconnected from the generator if an abnor-
mal condition of voltage, frequency, or load develops.
B. Pull-out Trays
The control box is equipped with pull-out, drawer-type trays
(Fig. 6) which provide easy access to con-
trols and equipment mounted in them. Each tray may be removed as an assembly by disconnecting a
single quick-disconnect connector and tripping two safety latches.
C. Voltage Regulator
The voltage regulator provides automatic voltage regulation at the aircraft. The regulator is adjustable
for a variety of output cable sizes and lengths. Depending on the Specification Number of the particu-
lar generator set, the voltage regulator may be either a magnetic amplifier type or a solid state elec-
tronic type. The Generator Set Identification Chart on Page 5 shows which voltage regulator a
particular generator set specification requires.
D. Test Circuitry
A receptacle connector
(19, Fig. 9) with wiring to various test points throughout the electrical circuitry
is provided for the attachment of a test box manufactured by Hobart Brothers. This test circuitry al-
lows electricians to perform as many as twenty-four tests and checks from one location, conveniently
and easily.
E. Electric Governor
The engine is equipped with an all electric type governor kit
(5and12,Fig.3) and other special equip-
ment more fully described under the engine description.
F. Low Fuel Level Shutdown Switch (Specification 6910B-4 and Specification 6910C-4)
On a Specification 6910B-4 unit or Specification 6910C-4 unit, which is mounted on a fifth-wheel
trailer, the fuel tank is equipped with a low fuel level shutdown switch. This switch is placed at such a
point in the tank that, when the fuel level is low, the switch opens a relay
(located on the back of the
generator control box)
which opens the fuel valve solenoid on the engine, cutting off fuel to the en-
gine. This low fuel shutdown circuit is shown on Schematic Diagram 180893, in the lower right corner
of the diagram, in Chapter 6. Circuit components are identified on the diagram as follows:
S54 Low fuel level switch
K65 Low fuel level relay
L7 Fuel valve solenoid
CR30 Low fuel level flyback diode
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PHYSICAL
BASIC UNIT
Length overall 88 inches
(2235 mm)
Width 36 inches (914.4 mm)
Height overall 43 inches (1092.2 mm)
Weight 3500 pounds (1496.8 kg)
FOUR-WHEEL TRAILER-MOUNTED UNIT
Length overall 100 inches
(2540 mm)
Width 78 inches (1981.2 mm)
Height 72 inches (1828.8 mm)
Weight 5400 pounds (2358.7 kg)
FIFTH-WHEEL TRAILER-MOUNTED UNIT
Length overall 131 inches
(3327mm)
Width 78 inches (1981mm)
Height 70 inches (1778mm)
Weight 4840 pounds (2195 kg)
GENERATOR
Output power rating 90 KVA
Output voltage 115/200 V
Rated load capacity 260 A
Frequency
(cycles-per-second) 400 Hz
Output kilowatts 72 KW
Power factor 0.8 PF
Duty cycle 100%
Operating speed at 400 Hz 2000 RPM
Overload capacity
(125% of rated load capacity) 325 A
GENERATOR PROTECTIVE SYSTEM
Overvoltage relay ** trips 130 V to 134 V; resets 125 V
Undervoltage relay trips 102 V or below; resets 110 V
Overfrequency relay ** trips 415 Hz to 425 Hz; resets 410 Hz
Underfrequency relay * trips 375 Hz to 385 Hz; resets 385 Hz
Overload relay trips 112 KVA in less than 5 minutes
Undervoltage time delay relay 4 to 12 seconds
* This relay is available with an optional time delay. For details refer to Paragraph 7, E, (2), (a).
** For these relays an optional memory and time delay PC module is available. For details refer to
Paragraph 7, E, (2), (a).
Specifications and Capabilities
Figure 2 (Sheet 1 of 2)
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ENGINE
Manufacturer/Model John Deere, Model 6059TL
Type Turbocharged, In-line, 6-cylinder,
4-cycle Diesel
Displacement 359 cu. in.
(5.9 liters)
Compression ratio 16.8:1
Firing order 1-5-3-6-2-4
Number of main bearings 7
Horsepower at 2000 RPM 123
Governed speed 2000 RPM +/- 4.5%
Idle speed 850 RPM +/-25 RPM
Electrical system 12 volt
Oil capacity
(with filter) 18 quarts (14 liters)
Oil capacity (without filter) 146 quarts (13.6 liters)
Coolant capacity (approx.) 20 quarts (19 liters)
Fuel Diesel oil conforming to ASTM Spec.
D.975-66T, Nos. 1-D and 2-D
(Diesel oil No. 1, No. 2, or Jet A-1)
Lube oil MIL-L-2104C or MIL-L-2104D
Specifications and Capabilities
Figure 2 (Sheet 2 of 2)
4. Identification
A. General
Generator sets are identified by their Specification number which consists of the Series number plus
a dash number
(i.e. -1, -2, etc.) suffix. The suffix number indicates the mounting design of the gener-
ator set. For example, Specification number 6910-1 identifies a machine designed for mounting on a
trailer or truck.
SPECIFICATION DESCRIPTION
6910-1, 6910A-1, Basic unit for trailer or truck mounting, with top exhaust, and equipped
6910B-1, 6910C-1 with a magnetic-amplifier type voltage regulator, Hobart Part No. 430391C.
6910A-2, 6910B-2 Basic unit for trailer or truck mounting, with top exhaust, and equipped with
6910C-2 a solid-state voltage regulator, Hobart Part No. 489812A.
6910A-3, 6910B-3 Fixed unit with fuel tank and batteries for truck mounting only. Equipped
6910C-3 with a solid-state voltage regulator, Hobart Part No. 489812A.
6910B-4, 6910C-4 Basic unit for mounting on 5th-Wheel Trailer, with special features.
Equipped with solid-state voltage regulator, Hobart Part No. 489812A.
6910C-5 Basic unit for tractor mounting. Equipped with solid-state voltage regu-
lator, Hobart Part No. 489812A.
(Voltage regulators are covered by manuals in Chapter 6).
Generator Set Identification Chart
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5. Optional Equipment
Several items of optional equipment are available for units covered by this manual. Each optional item is
covered by its own Instruction and Parts Manual and will not be covered in this basic manual. When appli-
cable, information for optional equipment will be located in Chapter 5. Options are listed as follows:
A. Trailers
A four-wheel trailer with batteries and fuel tank is available, and also a fifth-wheel trailer.
B. Transformer-Rectifier
A transformer-rectifier
(T-R) is available for use with the generator set. This T-R receives 115/200-V,
400-Hz, AC power from the generator and converts it to a 28.5 V DC output.
C. Truck
Trucks with special bodies for mounting the generator set are available. Compartments in the body
are provided for batteries, cable-storage, etc. Trucks available are Ford, Chevrolet, and GMC.
D. Second Output and Control Box
An auxiliary output and control box is available to provide a second independent 115-V AC output cir-
cuit.
E. Quick Start Kits
(See Section 1-3, Para. 2C)
F. Memory and Time Delay PC Board (Part No. 282308)
In a Hobart generator set, the memory and time delay module is an integral part of the circuitry that
protects the aircraft electrical system against damage which could result from overvoltage, undervol-
tage, overfrequency, or underfrequency. A voltage sensing module and a frequency sensing module
are connected to generator output leads between the generator and load contactor. These solid-state
modules sense any abnormal condition of voltage or frequency and signal the solid-state circuitry of
the memory and time delay module to open the load contactor and disconnect output to the aircraft.
For overvoltage, overfrequency and underfrequency conditions, the memory and time delay module
functions instantly to open the load contactor and disconnect output to the aircraft. But a unit
equipped with the special memory/time-delay module 282308
(depending on the DASH NUMBER
selected)
permits various lengths of time delay for opening the load contactor at the occurance of ab-
normal conditions of voltage or frequency. When selected, this option is explained in detail in TO-
210, which would be found in Chapter 5 of this manual.
6. Canopy
This generator set is equipped with a sheet metal enclosure, identified as a canopy (1, Fig. 1), which pro-
vides protection for the engine, generator and electrical controls. This canopy has doors on both sides.
Panel mounted instruments may be observed through two Plexiglass windows in the left rear door which
covers the control box and engine control panel. The lower window is slanted outward at the bottom to
provide access to engine controls when the door is closed. A centrally-located lifting eye attached to a lift-
ing yoke extends through the canopy top to provide an attaching point for chains, cables, or hook used to
lift and move the generator set.
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