Power Generation System and Troubleshooting of Caterpillar Generator

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1.0 Background
Today's power generation industry demands a strong back-up at all the times. To satisfy those demands, they require a reliable source of power from a trustworthy source. According to their specific needs, finding a good power generator will not be a problem from now onwards.
Whenever there is a power generation requisite, whether it is standby, continuous, emergency or prime, Caterpillar has a proven solution, because Caterpillar serve the power generation industry for more than 80 years. Experience the high power with low emissions. As the global supplier of power generator equip, Caterpillar is ready to take the challenge in the industry of power generation.
Diesel generating plants have an important role in power plants as well as in industries and commercial installations to meet continuous and emergency standby power requirements. A good knowledge of basic operation principles, layout requirements, associated components and maintenance practices for diesel power plants help the career development of many engineers and technicians in today's demanding world.
Broad Objective
The broad objectives of this report are mainly to understand power generating system, operation, maintenance and troubleshooting of Caterpillar generators.
Specific Objectives:
      The specific objective of this report includes:
v  To observe the different parts of alternator.
v  To observe the basic Diesel engine
v  To study Troubleshooting of alternator
1.1   About Zarina Composite Textile industries Ltd.
Company name:  Zarina Composite Textile industries Ltd
Factory Address: Nishatnagar, Tongi, Gazipur.
Products Manufacturing: All type of Knitted fabrics and Garments.
Corresponding Language: English
Price Standard: High, Medium.
Capacity per Month: 750, ton per Month.
Plant Production/Generation: 4MW
Floor area: 100000 SFT
Number of Stuff: 75
Number of Workers.1025
1.2 Membership

  • Bangladesh Garments Manufactures & exports Association.
  • Bangladesh Textile Mills Association
  • A member of Annanda
1.3 Mission & Vision
To produce the highest quality fine and super-fine count cotton yarn in the world, to provide best in customer service in the industry. To ensure consumers rate our yarn as first with regards to loom efficiency
1.4 Different type Machinery
Machine Name                                       Sets                        Brand                                Origin
Plain M/C                                                100                       Brother                               Japan
Over Lock four Thread                            80                            Pegasus                               Japan
Cylinder Bed                                             30                        Pegasus                                 Japan
Flat lock Flat Bed                                       10                  Pegasus                                     Taiwan
Feed of Arm                                          02                          Brother                                    Japan
Kansai Special (PMD)                           02                         Kansai                                      Japan
Rib Cutter                                            03                     PL-LU                                         Taiwan
Button Hole                                           02                         Brother                                     Japan
Button Switch                                        02                          Brother                                    Japan
Cutting Machine                                   04                                KM                                          Japan
Pico Ting                                                   01                         Brother                                       Japan
Bartek                                                  01                       Brother                                         Japan
Flat lock Cylinder bed                      05                       Pegasus                                         Japan
Snap Button machine                       05                         Brother                                         Japan
Electric Boiler                                 01                  Long chuan                                   Taiwan
Steam Iron                                          25                     Namoto                                          Japan
Vacuum Table                                     25                     Namoto                                   Indonesia
Thread sucker                                      01                  Ngaishing                                         China
Needle Detector                                 `01                     Kaiju                                                China
PP Strapping                                        01                      Toyo                                               Taiwan
Four cone Thread Winding                      01                      Kaiju                                              China
Spot Remover                                           02                                                                             China
1.5 Technical Factors
 Highly Experienced Technical in all level.
 Selection of best quality yarn.
 Timely delivery & ensure quality products.
1.6 Compliance Factors
ü  Fully Air condition & dust free floors
ü  All floors are tiled
ü  2 set of stairs
ü  Main stair – 10 ft wide
ü  Emergency stair -6.5 ft wide
ü  Doctor Room
ü  Day Care Center
ü  Pure Drinking water Facility in each floor
ü  Fire Control & Water hydrant system
ü  Adequate dining space
ü  Prayer room in each floor
ü  Restriction on Child Labor
1.7 Commitment to Customer
Our success is based upon our customer focus. We listen to and connect with customers. We anticipate their needs and make it easy for them to do business with us. We keep promises. We offer them value and quality services to enrich lives and enhance business success. We treat them with dignity and respect.
 1.8 Human Resource Management Computerized System (HRMCS)
The Company exercise equal employment opportunity in the recruitment and selection Process.  No discrimination is made due to race, sex, caste, creed, color or religion.
Employee Evaluation
The evaluation is based on a measurement of employee’s performance against established objectives. It is a guide for regularization, conformation, promotion & realignment.
The Company provides Group Life Insurance coverage for all its employees as a protection against death and/or disability with ALICO plan.
The Company Maintains Medical facilities to ensure employee's health, safety and medical needs. Also provides hospitalization benefit through medical insurance premiums are paid by the company.
It is the Company Policy to provide safe working areas for all employees. Employees are provided with free sets of coveralls/uniforms, hardhats, safety shoes, earmuff, must wear during work.
1.9 Quality Commitment
Zarina Composite Textile Industries Ltd. is committed to operating a successful business by developing, manufacturing, marketing and supporting quality yarn products for the world textile industry. Zarina Composite Textile Industries Ltd. is keen to accomplish this goal by:
Ø  Developing long-term relationships with our customers and suppliers.
Ø  Providing superior quality products at competitive prices.
Ø  Exceeding industry standards with exceptional customer and technical service.
Ø  Maintaining our competitive position through leading edge technology.
Ø  Providing a safe, fulfilling, and rewarding work environment for our employees.
Ø  Serving and supporting the communities in which we operate.
1.10 Company Organogram

2.1 Definition of Generator
A generator is a machine that converts mechanical energy into electrical energy. Generators can be subdivided into two major categories depending on whether the electric current produced is alternating current (AC) or direct current (DC). The basic principle on which both types of generators work is the same, although the details of construction of the two may differ somewhat.
A diesel generator is the combination of a diesel engine with an electrical generator or alternator to generate electrical energy. The excitation of the generator is controlled by an automatic voltage regulator, installed in the control cabinet of the generating set. Diesel generating sets are used in places without connection to the power grid. Generators are useful appliances that supply electrical power during a power outage and prevent discontinuity of daily activities or disruption of business operations. Generators are available in different electrical and physical configurations for use in different applications.
Generator = Prime mover / Engine + Alternator


                                             Alternator          Engine
Figure 2.1: Caterpillar Diesel Generator (D 3512B) Set
2.2 Principle of Electrical Generator
Generator works on the principle of electromagnetic induction discovered by Michael Faraday in 1831-32. Faraday discovered that the above flow of electric charges could be induced by moving an electrical conductor, such as a wire that contains electric charges, in a magnetic field. This movement creates a voltage difference between the two ends of the wire or electrical conductor, which in turn causes the electric charges to flow, thus generating electric current.
There are three basic requirements for the generation of voltage: magnetism, motion, and conductors. The generator system is based on the concept that when a coil moves relative to a magnetic field, a voltage is produced. You may remember that when a conductor cuts through a magnetic field a current is produced in that conductor. These two concepts are very closely connected. Also, keep in mind that it makes no difference whether the magnetic field is stationary and the conductor moves or whether the conductor is stationary and the magnetic field moves. There just needs to be relative motion. The simplest generator consists of a loop of wire rotating between two permanent magnet poles.
2.3 Main Components of a Generator
An AC synchronous generator is significantly more complex than the simple generator of a wire loop rotating between two permanent magnets. An AC synchronous generator consists of four main components and/or systems:
  Ø  Field (rotor)
  Ø  Armature (stator)        
  Ø  Exciter
  Ø  Automatic Voltage Regulator
Essentially the process of generating voltage goes in the following order. The exciter provides DC current to the rotor windings. DC current through these wires creates flux. This flux generates voltage in the nearby stator windings when there is relative motion between the two. The regulator then senses this output and controls the exciter current. In Caterpillar generators, the rotor (the source of the magnetic field) rotates inside a stationary armature called a stator. One reason for using a stationary armature and a rotating magnetic field is the difficulty of taking 3-phase current from a rotating armature. The rotor is rotated by a prime mover.  The rotor contains magnetic poles with windings wrapped around them to form coils. These coils are called field coils or field windings because they create a magnetic field when excited with a DC current. Typically the field windings in a generator contain several hundred turns.
A magnetic field radiates out from the rotor as lines of flux. As the rotor rotates, so does the magnetic field. When this moving magnetic field comes across a stator winding voltage is produced. The magnetic field is strongest at the north and south poles where the lines of flux are concentrated. Therefore, the closer a pole is to a stator winding, the higher the voltage produced in that stator winding.
The symmetrical design of the generator ensures that the rotor poles extend over equal arcs and that the flux density distribution is similar across all stator windings.

Magnetic poles refer to the magnetic north and south and are the points where the magnetic field is strongest on the rotor.

Figure 2.3: North Pole and South Pole
A pole relates to the number of magnetic poles developed in the rotating field. Magnetic poles in a four-pole generator are arranged north-south-north-south around the circumference of the rotor. The number of poles (north-south- north-south) and the desired frequency (cycles per second or hertz) determine the synchronous or no-load speed in revolutions per minute (RPM):
RPM = 120 2 f/number of poles
If 50 Hz is desired from a four-pole generator, the generator must be driven at 1500 rpm.
A six-pole generator is driven at 1000 rpm:
The generated frequency of 50 Hz is entirely a function of the driven speed.
1000 rpm= (120 × f)/6=50
The relationship between the number of poles and the synchronous speed is shown in the table below. These calculations are figured by taking the fundamental frequency of 50 or 60 Hz and dividing it by the number of pole pairs. It is then multiplied by 2π to get the synchronous speed into rad/s that is then converted into rpm.

Table 2.3: Synchronous Speed                                                              
Regardless of the number of pole pairs, the rotor moves 360 mechanical degrees in one revolution. In electrical degrees, however, each pole pair rotates 360 mechanical degrees. In other words, electrical degrees are the mechanical degrees times the number of pole pairs. In a four-pole generator (two pole pairs), each pole pair moves 360 mechanical degrees, so the total electrical degrees moved is 720 (or 360 × 2).
Mech. Degrees × No. Pole Pairs
2-pole: 360° electrical
4-pole: 720° electrical
6-pole: 1080° electrical
8-pole: 1440° electrical
The main armature, or the stator, remains stationary. The stator consists of the stator core, exciter field coils, and its own windings called stator windings, or armature windings. The stator windings are placed in slots along the inside of the stator. The stator usually contains a large number of slots. The rotor magnetic field cuts across the stator windings as it rotates inside the stator. As a result, voltage is produced in these windings. The closer a winding is to a pole face on the rotor, the point where magnetic field is the strongest, the higher the voltage produced in that stator winding. The stator voltage is the generator output that is supplied to the load.
2.4 Magnetic Field and Voltage
The magnetic field is induced in the main generator by a DC current from the exciter through low voltage field or rotor windings. These windings are low voltage compared to the stator windings.DC voltage as high as 250V is often used in larger generators, while smaller and medium sized generators seldom use voltages higher than 125V.
Because it is so difficult to extract high voltage from a rotating armature, the magnetic field of the main generator is rotated rather than the armature.  Generator output voltage depends on the following:

  1. Speed of relative motion between magnetic field and stator conductors
  2. Strength of magnetic field
  3. Number of series turns in the stator windings
The strength of the magnetic field is proportional to the current flowing through the field coils. As the current rises, the magnetic field grows stronger.
The speed of relative motion between the magnetic field and the stator windings depends on the rotational speed of the rotor (engine rpm). As the rpm rises, so does the speed (V) of relative motion. The higher the speed of relative motion, the greater the generators output capabilities.
Voltage can be adjusted by arranging the stator windings in coils and varying the number of turns, or times the windings are wound around the stator. The higher the number of turns, the higher the voltage induced. The lower the number of turns, the lower the voltage induced. Hence, stator windings can be arranged with the optimum number of coil turns to produce the required output voltage.
2.5 Phase and Voltage
This section demonstrates the ways in which phase, voltage, and the stator core are all inter-dependent. The calculated design of the stator core and winding distribution enables a generator to provide the appropriate output voltage.
The phase voltage of a generator is directly linked to the voltage output of that generator. The type of voltage induced is partially dependent on the number of phases in a generator.
A three-phase generator consists of three coils equally spaced around the stator and connected in a wye (Y). Therefore, three voltages can be produced consecutively with a 120° phase difference.
In three-phase generation, three phases of voltage are produced 120° apart. However, to make the connection a symmetrical 3-phase connection, the B phase coil for example, has an equal and opposite winding 180° away, referred to here as -B. The result is that the three phases and their opposing windings are actually 60° apart.

Figure 2.5: Phase angle
2.6 Basic Theory of Brushless Alternator
When an electric current is passed through a coil of wire, a magnetic field is produced (an electromagnet).Conversely, when a magnetic field is moved through a coil of wire, a voltage is induced in the wire. The induced voltage becomes a current when the electrons have some place to go such as into a battery or other load. Both of these actions take place in generator. Voltage is generated when a coil of wire is moved through a magnetic field.
It doesn’t matter whether the coil is moving or the magnetic field is moving. Either configuration works equally well and both                
Figure 2.6: 3-Phase Brushless Alternator
are used separately or in combination depending on mechanical, electrical and other objectives. Automotive alternators use the opposite configuration with a rotating field and stationary armature. In a brushless alternator, both configurations are used in one generator.
2.7 Caterpillar Generator
Figure 2.7A: Exterior view Caterpillar generator (left side)
The main components of a Caterpillar generator can be broadly classified as follows (external view):
     1. Control panel   2. Alternator   3. Oil filler cap 4. Oil level gauge   5. Oil filter  
     6. Secondary fuel filters  7. Water drain  8. Oil screen    9. Oil drain plug
    10. Cooling system filler cap  11. Crank case Breather    12. Exhaust  13. Starting motor
    14. Air cleaner 15. Generator terminal box 16. Exhaust cover (alternator)
     18. Air inlet cover    (alternator)

Figure 2.7B: Exterior view Caterpillar generator (right side)

2.7.1Generator Specification
Engine data
Engine Model #3512 B
Arrangement No: 2120324       
Cylinder: 12
1714 KVA     1200KW 50 Hertz
Generator data:
Alternate Gen Rating 1900KVA
Alternator type: Brushless
Phase: 3, 6 wire
Power factor:   0. 8
Generator 600 volts 1649 Amps
Excitation: 34 volts 7.38 Amps
Excitation type: Brushless
RPM: 1500
Voltage regulator: Auto
Maximum ambient temp.: 40 o C
Cooling system: Radiator type
Insulation: Class H
Gen: S/N: 7TN3715
ESO: DLZPN                                                    
                                                                              Figure 2.7.1: Caterpillar Generator
3.1 Caterpillar Diesel Engine
The D3512b Caterpillar engine is configured as 12 combustion chambers and four-cycle to drive auxiliary generators. The engines designed as “V” shape. The “V” configuration is favored when there is a lack of space because “V” engines are shorter and more compact than in-line engines. A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber during the final stage of compression. This is in contrast to a petrol engine or gas engine, which uses the Otto cycle, in which a fuel/air mixture is ignited by a spark plug.
It operates using the diesel cycle. Diesel engines have the highest thermal efficiency of any internal or external combustion engine, because of their compression ratio. Diesel engines are manufactured in two stroke and four stroke versions. They were originally used as a more efficient replacement for stationary steam engines.
3.2 Engine main Parts
The basic components of a Caterpillar diesel engine are given bellow:

  1. Engine Block
  2. Valves
  3. Piston
  4. Cylinder liner
  5. Crank shaft
  6. Fly wheel
  7. Cylinder head
  8. Crankcase
  9. Main bearing cap
  10.  Cylinder head gasket

3.2.1 Engine Block
Figure 3.2.1: Engine Block
In a four-stroke engine, the engine block includes the crankshaft, connecting, camshafts, and valves. There are one or more cylinders, and for each cylinder there is a spark plug, a piston , and a crankpin .
3.2.2 Valves

Figure 3.2.2: Valves
The valves control the admittance of fuel and air into the combustion chamber.       
3.2.3 Piston

Figure 3.2.3: Piston
A piston is a component of reciprocating engine. It is located in a cylinder and is made diesel-tight by piston rings. Its purpose is to transfer force from expanding diesel in the cylinder to the crankshaft via a piston rod and/or connecting rod
3.2.4 Cylinder liner
Figure 3.2.4: Cylinder Liner
A cylinder liner is a cylindrical part to be fitted into an engine block to from a cylinder. It is one of the most important functional parts to make up the interior of an engine.
3.2.5 Cylinder head
Cylinder head
Figure 3.2.5: Cylinder head
In the internal combustion engine, the cylinder head sits atop cylinders and consists of a platform containing part of the combustion chamber and the location of the valves and injector.
3.2.6 Crankshaft
Figure 3.2.6: Crankshaft
The reciprocating internal combustion engines end up turning a shaft. This means that the linear motion of a piston must be converted into rotation. This is typically achieved by a crankshaft.

3.2.7 Flywheels
Figure 3.2.7: Flywheel
The flywheel is a disk or wheel attached to the crank, forming an inertial mass that stores rotational energy. In engines with only a single cylinder the flywheel is essential to carry energy over from the power stroke into a subsequent compression stroke. Flywheels are present in most reciprocating engines to smooth out the power delivery over each rotation of the crank and in most automotive engines also mount a gear ring for a starter. The flywheel may also perform a part of the balancing of the system and so by itself be out of balance, although most engines will use a neutral balance for the flywheel, enabling it to be balanced in a separate operation. The flywheel is also used as a mounting for the clutch or a torque converter in most automotive applications
3.2.8 Crankcase
Figure 3.2.8: Crankcase
In a piston engine, the crankcase is the housing for the crankshaft. The enclosure forms the largest cavity in the engine. Separated from the cylinder by the reciprocating piston.
3.2.9 Main bearing cap
Figure 3.2.9: Main bearing cap
This is an element which is use to increase the life of moveable parts. It is used in Crankshaft. It is one kinds of journal bearing called main bearing at the top which is called bearing cap.
cylinder head
3.2.10 Cylinder head gasket
Figure 3.2.10: Cylinder head gasket
A head is a gasket that sits between the engine block and cylinder head in an internal combustion engine. Its purpose is to seal the cylinders to ensure maximum compression and avoid leakage of coolant or engine oil into the cylinder.
3.3 Operation
The series of events taking place in a four-cycle engine are: inlet stroke, compression stroke, expansion or power stroke, and exhaust stroke. Four strokes (two revolutions of the crankshaft) are necessary to complete the cycle.

Figure 3.3A: Cross section of an engine
Inlet stroke
As the piston starts downward from TDC, the inlet (intake) valve opens and allows the piston to suck a charge of fresh air into the cylinder. This air may be supplied at a pressure higher than atmospheric air by a supercharger.
Compression stroke
As the piston nears BDC, the air inlet valve closes, sealing the cylinder. Energy supplied by the crankshaft from a flywheel, or power from other cylinders, forces the piston upward toward TDC, rapidly compressing the air and increasing the temperature and pressure within the cylinder.

Figure 3.3B: Four Stroke Cycle
Power stroke
As the piston approaches TDC, an amount of fuel (modulated by the governor) is injected (sprayed and atomized) into the cylinder which is ignited by the high temperature, and combustion starts. Combustion, at a controlled rate, further increases the temperature and pressure to accelerate the piston toward BDC. The expansion of the hot gases forces the piston down and turns the crank against the load. Engine efficiency depends on the fuel charge being completely burned during the power stroke.
Exhaust stroke
As the piston passes through BDC at the end of the power stroke, the exhaust valve opens. The piston, using stored energy from the flywheel or from the power stroke of another cylinder, forces the burned gases from the cylinder through the exhaust port. As the piston approaches TDC, the exhaust valve is closed and the air intake valve opens to begin another cycle.
3.4 Starter System

Figure 3.4: Starting Motor
All internal combustion engines require some form of system to get them into operation. The engines use a starter motor powered by the 15 psi external air pressure. The engines are started with a compressed air motor that is geared to one of the engine's drive shafts.
3.5 Radiator Cooled System

Figure 3.5: Radiator Cooled System
A radiator fan is coupled with the engine for the radiator cooling system. Combustion generates a great deal of heat, and some of these transfers to the walls of the engine. Failure will occur if the body of the engine is allowed to reach too high a temperature; either the engine will physically fail, or any lubricants used will degrade to the point that they no longer protect the engine. Cooling systems usually employ air (air cooled) or liquid (usually water).
3.6 Lubrication System
Internal combustions engines require lubrication in operation that moving parts slide smoothly over each other. Insufficient lubrication subjects the parts of the engine to metal-to-metal contact, friction, heat build-up, rapid wear often culminating in parts becoming friction welded together with pistons in their cylinders. Big end bearings seizing up will sometimes lead to a connecting rod breaking and poking out through the crankcase.
3.7 Air inlet and Exhaust System

Figure 3.7: Air Inlet and Exhaust System
Internal combustion engines have to manage the exhaust of the cooled combustion diesel from the engine. The exhaust system frequently contains devices to control pollution, both chemical and noise pollution. In addition, for cyclic combustion engines the exhaust system is frequently tuned to improve emptying of the combustion chamber.
3.8 Control System
Most engines require one or more systems to start and shutdown the engine and to control parameters such as the power, speed, torque, pollution, combustion temperature, efficiency and to stabilize the engine from modes of operation that may induce self-damage such as pre-ignition. Such systems may be referred to as Engine Control Unit (ECU).
3.9 Electronic Fuel Injection System
The Electronic Unit Injection (EUI) Engine Controls used in The Caterpillar Diesel Generator. The EUI engines have many features and benefits not possible with mechanical fuel systems. These features include a very clean exhaust, improved fuel consumption and cold starting, simplified maintenance with fewer moving parts, and reduced operating costs.

    Throttle control
    Pressure sensor
    Temperature sensor
    Speed/timing sensor
Figure 3.9: Electrical and Electronic Components in EUI system
This slide shows six major types of electrical/electronic components in the EUI fuel system:

  1. ECM
  2. Throttle Control
  3. Pressure Sensor
  4. Temperature Sensor
  5. Speed/Timing Sensor
  6. Injector
The timing is controlled by the ECM. Engine speed and fuel quantity (which relates to load) inputs are received by the timing control. These combined inputs determine the start of fuel injection.
The timing control provides the optimum timing for all conditions. The benefits of a "smart" timing control are:
  1. Reduced particulates and lower emissions
  2. Improved fuel consumption while still maintaining performance
  3. Extended engine life
  4. Improved cold starting

Three inputs control fuel quantity:

  1. Engine speed
  2. Throttle position
  3. Boost
These signals are received by the electronic governor portion of the ECM. The governor then sends the desired fuel signal to the fuel injection control. The electronic governor also receives signals from the fuel ratio control and torque control.
Two variables determine fuel quantity and timing:
  1. The start of injection determines engine timing.
  2. The injection duration determines the quantity of fuel to be injected.
The Speed/Timing Sensor serves three basic functions in the system:
  1. Engine speed measurement
  2. Engine timing measurement
  3. Cylinder identification and TDC location
3.10 Electronic and Electrical Components of Caterpillar Diesel Engine
There are some electronic and electrical components to increase the engine performance and reduce maintenance cost. The components are described below:
3.10.1 Electronic Control Module                                                                                  
The principal component in the EUI system is the Electronic Control Module (ECM). The ECM is mounted at the front of the engine. The ECM is the "heart" of the engine. The ECM performs engine governing, timing and fuel limiting. It also reads sensors and communicates to the instrument display system through the CAT Data Link.

Figure 3.10.1: Electronic Control Module (ECM)
The ECM receives all the signals from the sensors and energizes the injector solenoids to control timing and engine speed. The ECM is sealed except for access to the software which is contained in the Personality Module. This ECM is the second generation of Advanced Diesel Engine Management Systems and is often referred to as "ADEM II."
The ECM has an excellent record of reliability. Therefore, any problems in the system are most likely to be in the connectors and wiring harness. In other words, the ECM should typically be the last item in troubleshooting.

3.10.2 Personality Module


Personality Module
Figure 3.10.2: Personality Module
The Personality Module contains the software with all the fuel setting information (such as horsepower, torque rise and air/fuel ratio rates) which determines how the engine will perform. The Personality Module is installed on the lower face of the ECM, behind the access panel.
There are two methods can be used to update the software:
     1. Remove and replace the Personality Module.
     2. Flash Programming: Electronic reprogramming of the Personality Module.
The ECM is sealed and needs no routine adjustment or maintenance. The Personality Module is mounted within the ECM. Installation of the Personality Module is the only reason to enter the ECM. This operation would normally be performed during an ECM installation or a software update. It should be noted that, if a Personality Module is not installed in the ECM or is not flash programmed, the ET Service Tool will not be able to communicate with the ECM.
3.10.3 Data Link
Figure 3.10.3: Link between various microprocessor based systems
The Data Link provides a two-way communication path between the EUI. The  Data Link is the communication link between the ECM, EPTC II, Caterpillar Monitoring System, ET Service Tool, or PC based software and other onboard/off board microprocessor based systems. The Data Link also allows the ET service tool to communicate with the engine ECM.
3.10.4 Harness

Figure 3.10.4: Harness
The wiring harness provides two-way communication between the ECM and the engine sensors and connects the ECM to the unit injectors. The harness is routed from the ECM at the left front of the engine to the left side of the engine. The harness then crosses over to the right rear of the engine and is routed to the right side of the engine.
3.10.5 Coolant Temperature Sensor
The engine Coolant Temperature Sensor is located at the front of the engine on the thermostat housing. This sensor is used with the ECM to control various functions.


Figure 3.10.5: Coolant Temperature Sensor
The following systems or circuits use the Temperature Sensor output to the ECM:          

  1. Caterpillar Monitoring System Coolant Temperature Gauge over the CAT Data Link.
  2. The High Coolant Temperature Warning Alert Indicator and Gauge on the Caterpillar Monitoring System panel. (The information is transmitted over the CAT Data Link.)
  3. The Engine Demand Fan Control, if installed, uses the sensor signal reference to provide the appropriate fan speed.
  4. The Cat Electronic Technician (ET) status screen for coolant temperature indication.
  5. The Cold Mode engine control (elevated low idle and timing reference for cold mode operation).
3.10.6 Speed/Timing Sensor


Timing Wheel
Speed/Timing Sensor

Figure 3.10.6: Speed/Timing Sensor
 The Speed/Timing Sensor is mounted on the rear gear housing. This sensor is used to calculate engine speed and crankshaft position for timing purposes. The sensor is self-adjusting, but special precautions are necessary during installation to prevent damage. The Speed/Timing Sensor is mounted on the rear housing below the timing wheel. This sensor is self-adjusting during installation and has zero clearance with the timing wheel.
3.10.7 Fuel Injector

Figure 3.10.7: Fuel Injector
The injector is controlled electrically by the ECM. The signal from the ECM controls the opening and closing of the solenoid valve. The solenoid valve controls the flow of high pressure fuel to the cylinder.
This system enables the ECM to control fuel volume and timing. The injector has barred and numerical codes marked on the tappet. The numerical code must be entered into the ECM using ET. The purpose of this code is to ensure that all injectors are matched as perfectly as possible in performance, both in timing and fuel quantity. If an injector is replaced, moved to another position on the engine, or if two injectors are switched, then the injector codes must be reprogrammed. The injector codes are programmed into the ECM using ET and the Calibrate Sensor Screen. Failure to enter the codes into a new ECM may result in unequal timing and fuel delivery between cylinde
3.10.8 Fuel Pressure Regulator



     Fuel Pressure
Figure 3.10.8: Fuel Pressure Regulator
The Fuel Pressure Regulator is located on the top right side of the engine. Fuel flows from the fuel filter base, through the steel fuel lines, to the EUI fuel injectors. Return fuel from the injectors flows through the fuel pressure regulator before returning to the fuel tank. Fuel pressure is controlled by the fuel pressure regulator.
3.10.9 Atmospheric Pressure Sensor



     Pressure Sensor
Figure 3.10.9: Atmospheric Pressure Sensor
The Atmospheric Pressure Sensor is installed on the ECM mounting adapter and is vented to the atmosphere. Briefly, it performs the following functions:

  1. Ambient pressure measurement for automatic altitude compensation and automatic air filter compensation.
  2. Absolute pressure measurement for the fuel ratio control, ET, filter restriction, and Caterpillar Monitoring System panel (gauge) pressure calculations.
3.10.10 Turbocharger Inlet Pressure Sensor

    Inlet Pressure
              Figure 3.10.10: Turbocharger Inlet Pressure Sensor
The Turbocharger Inlet Pressure Sensor is mounted between the air filter and the turbocharger. This sensor is used in conjunction with the atmospheric pressure sensor to measure air filter restriction for engine protection purposes. The difference between the two pressure measurements is used as the filter differential pressure. The engine ECM uses this calculation to determine whether dreading is necessary to protect the engine against the effects of excessive filter restriction. This function is referred to as Automatic Air Filter Compensation.
Depending on the application and air intake system configuration, either one or two Turbocharger Inlet Pressure Sensors may be used. If the generator is equipped with an ether start system, the ECM will automatically inject ether from the ether cylinders during cranking. The operator can also inject ether manually with the ether switch in the cab. Ether will only be injected if the engine coolant temperature is below 10°C (50°F) and engine speed is below 1200 rpm.
3.10.11 Turbocharger Outlet (Boost) Pressure Sensor

     Turbocharger Outlet
        Pressure Sensor
Figure 3.10.11: Turbocharger Outlet Pressure Sensor
Also at the front of the engine in the vee is the Turbocharger Outlet (Boost) Pressure Sensor. This sensor is used with the ECM to control the air/fuel ratio electronically. This feature allows more accurate smoke control which was not possible with previous mechanically governed engines. The sensor reads boost pressure through a tube connecting the sensor to the manifold. The sensor also allows boost pressure to be read using the electronic service tools.
3.10.12 Exhaust Temperature Sensor
                   Figure 3.10.12: Exhaust Temperature Sensor
Exhaust Temperature Sensor is mounted below each turbocharger. These sensors are used to warn of possible damaging conditions in the engine caused by excessive exhaust temperature.
3.10.13 Filtered Lubrication Oil Pressure Sensor

   Filtered Lubrication
   Oil Pressure Sensor                            
Figure 3.10.13A: Filtered Lubrication Oil Pressure Sensor
Mounted on the rear of the Oil Filter Group is the Filtered Lubrication Oil Pressure Sensor. This sensor is used to signal oil pressure to the ECM. The sensor is also used by the ECM to generate low oil pressure warning for the operator.

Figure 3.10.13B: Unfiltered Lubrication Oil Pressure Sensor
Mounted at the front of the Oil Filter Group is the Unfiltered Lubrication Oil Pressure Sensor. This sensor is used by the ECM with the Filtered Lubrication Oil Pressure Sensor to calculate oil filter differential pressure. The oil filter differential pressure calculation provides a warning that the oil filters need to be changed. The oil filter differential pressure calculation provides a warning that the oil filters need to be changed.
3.10.14 Crankcase Pressure Sensor

Figure 3.10.14: Crankcase Pressure Sensor
A Crankcase Pressure Sensor may be mounted on the right side of the engine. This sensor is used to protect the engine by giving advance warning of a failure (i.e. a piston allowing excessive blow by which could soon cause considerable damage).
3.10.15 Timing Calibration Sensor

Timing Calibration

Figure 3.10.15: Timing Calibration Sensor
The Timing Calibration Sensor is installed when required for speed/timing sensor calibration in the flywheel housing. This sensor (magnetic pickup) is installed in the hole normally reserved for the timing pin. The pin is used to position the crankshaft.
3.10.16 Throttle Position Sensor
The Throttle Position Sensor provides engine speed control for the operator. At engine start-up, the engine rpm is set to low idle for two seconds to allow an increase of oil pressure before the engine is accelerated. The Throttle Position Sensor receives 8 Volts from the Digital Sensor Power Supply at the ECM.
3.11 ECM Power Supply
The power supply to the ECM and the system is drawn from the 24-Volt machine battery. The principle components in this circuit are:
– Battery
– Key Start Switch
– Main Power Relay
– 15 Amp Breaker
– Ground Bolt
– ECM Connector (P1/JI)
– Machine Interface Connector (J3/P3)
3.12 Speed/Timing Sensor Power Supply
The Speed/Timing Sensor has a dedicated power supply. The ECM supplies 12.5 ± 1 Volts to the Speed/Timing Sensor. Connectors A and B send the common power supply to the sensor. The C wire transmits a separate signal to the ECM. This power supply is not battery voltage, but is generated and regulated within 1.0 Volt by the ECM. This power supply and the Speed/Timing Sensor are vital parts of the EUI system. A failure of the sensor will result in an engine shutdown.
4.1 Alternator
The alternator, also known as the ‘genhead’, is the part of the generator that produces the electrical output from the mechanical input supplied by the engine. It contains an assembly of stationary and moving parts encased in housing. The components work together to cause relative movement between the magnetic and electric fields, which in turn generates electricity.
The stationary part of a motor or alternator is called the stator and the rotating part is called the rotor. The coils of wire that are used to produce a magnetic field are called the field and the coils that produce the power are called the armature.
4.2 Brushless Alternator
A brushless alternator is composed of two alternators built end-to-end on one shaft. Smaller brushless alternators may look like one unit but the two parts are readily identifiable on the large versions. The larger of the two sections is the main alternator and the smaller one is the exciter. The exciter has stationary field coils and a rotating armature (power coils). The main alternator uses the opposite configuration with a rotating field and stationary armature.

Figure 4.2: Brushless alternator
This can be confusing because most of us equate the armature with the rotor. Traditionally, the armature was the rotor but this is not necessarily the case. The two terms are not synonymous.
In the common automotive alternator, the field is on the rotor and the armature is on the stator. The rotor and stator are the mechanical configuration. The field and the armature are the electrical components. Either electrical component can be located on either of the two mechanical parts. The coils of wire that are used to create the field and the armature are sometimes referred to as the “windings”.
4.3 Components of Caterpillar Generator (Alternator)
The caterpillar generator consists of several parts to power generation. Some of its components are used for its protection and for receiving the electrical sense from corresponding equipment.


               Coupling plate                             Exciter field coil                           CDVR
                Shaft                                           Main alternator armature coil        PT
                Drive-End bearing                     Bearing Sensor                             Droop CT
                Armature cooling fan                Winding temperature Sensor         Bus terminal          
                Main alternator field coil          
                Exciter armature coil
                 Rotating rectifier                                                                                                                            
                 Non-Drive-End Bearing
Picture 015
4.3.1 Coupling Plate
This plate is located at the rear side of an alternator. The coupling plate coupled the alternator shaft with the engine shaft. It helps to rotate the alternator with the same rotation of the engine.
4.3.2 Shaft


Figure 4.3.2: Shaft
The rotating shaft transmits rotary motion from the engine to the exciter armature coil and main alternator field coil to produce mechanical energy to electrical energy.
4.3.3 Drive-End Bearing
      Drive End Bearing
Figure 4.3.3: Drive End Bearing
The bearing placed to the rear side of the alternator for smooth moving with the engine speed is known as Drive-End-Bearing. These types of bearing need to be greased after every 2000 hours of generator running. 
 4.3.4 Armature Cooling Fan

Armature Cooling
Figure 4.3.4: Armature Cooling Fan
This fan is attached with the shaft. It is used for saving the armature from overheated.
4.3.5 Main Alternator Armature Coil
Figure 4.3.5: Main Alternator Armature Coil
This is stator part and constructed with copper cored insulation. This armature covers the main alternator field coil. It cuts the electromagnetic flux and produces the EMF. It transfers the produced EMF through the 3-phase line.
4.3.6 Main Alternator Field Coil
Left view                 Armature Coil                                               
Right view

Figure4.3.6: Main Armature Field Coil
Main alternator field coil is fixed with the shaft as rotor. It is a 4 pole coil, two are north poles and two are south poles. It is constructed with iron and copper cored insulation. It collects excitation voltage from the exciter armature coil through the rectifier group and creates electric flux.
4.3.7 Rotating Rectifier Group

Figure 4.3.7: Rotating Rectifier Group
Rotating rectifier group is placed between exciter armature coil and main alternator field coil. The rectifier group consists of three positive diodes and three negative diodes. It converts the a.c voltage to d.c voltage. It also acts as a safety instrument for main alternator coil and saves from over excitation voltage.
4.3.8 Exciter Armature Coil and Exciter Field Coil
      Exciter Armature Coil
       Exciter Field Coil
Figure 4.3.8: Exciter Armature Coil and Field Coil
The exciter field coils (8 poles) are on the stator and its armature is on the rotor. The AC output from the exciter armature is fed through a set of diodes that are also mounted on the rotor to produce a DC voltage. This is fed directly to the field coils of the main alternator, which are also located on the rotor. With this arrangement, brushes and slip rings are not required to feed current to the rotating field coils.
4.3.9 Varistor
The varistor is placed between rotating rectifier and main alternator field coil. It acts as a protective device for the alternator field coil. Its resistance is over than 15000 ohms.
4.3.10 Bearing Speed Sensor

Figure 4.3.10: Bearing Sensor (left – exterior view), (right- interior view)
Bearing sensor capable of detecting shaft speed, acceleration, rotation, and angular position. These units have a robust and simple design, offering high signal accuracy and reliability, compactness, and ease of assembly.
The code ring, linked with the rotating inner ring, is magnetized with a sequence of north and south magnetic poles. The number of digital pulses equal to the number of pole pairs on the impulse ring is generated on each revolution. The output signal is transmitted to the CDVR by a connecting cable and connectors integrated into the bearing’s sensor.
4.3.11 Winding Temperature Sensor
   Figure 4.3.11: Winding Temperature Sensor
Bearing sensor RTDs are tubular, tip sensitive sensors in which the sensing element is encased in a copper alloy tip. This allows for increased accuracy and sensitivity to temperature changes at the point of contact in bearings. Inserted at an opening on the bearing housing, they are used for continuous sensing of the bearing’s temperature. Normally six sensors are recommended for each motor, Two per Phase.
ü  Slim dimensions to get inserted in between windings
ü  Resistance to shock, vibration and pressure
ü  High Dielectric Strength
4.3.12 CDVR
The full meaning of CDVR is CAT Digital Voltage Regulator. CDVR acts as a central monitoring unit for alternator. The digital voltage regulator (DVR) is the digital version of Caterpillar’s voltage regulators. It RMS sensing is standard on this package which gives it better capabilities. It is typically used in medium to larger sized generator sets. It can provide superior Volts/Hertz regulation since it can be programmed to be application specific.


Figure 4.3.12: CAT Digital Voltage Regulator
CDVR Specification
Control power input: 13-30 VDC, 5 VP
1 phase power input: 100-200 VAC, 50 Hz
3 phase power input: 80-280VAC, 50 Hz
Sensing input: 90-600 VAC, NOM, 50 or 60 Hz
Paralleling input: 5 A, AC, 50 or 60 Hz, .2 VA
AC input:-10 to 10 VDC, 0.0012VA
Out put: 63 VDC, 12 A
 Protective Functions:
ü  Generator Over voltage
ü  Generator Under voltage
ü  Loss of Excitation
ü  Instantaneous Field Over current
ü  Over Excitation
ü  Loss of Sensing
ü  Diode Fault Monitor
ü  Internal Watchdog Failure
ü  Internal Memory Failure
ü  Fault Reset Closed Too Long
4.3.13 Potential Transformer



Figure 4.3.13: Potential Transformer (PT)
There is a potential transformer placed between alternator bus bar and CDVR. It takes the voltage from bas bar terminal and transfers to the CDVR. It reduces the bus bars high voltage to low voltage for CDVR sensing.
4.3.14        Droop Current Transformer

  Droop CT
Figure 4.3.14: Droop CT
A droop CT is attached with the generator terminal. This type of ct helps the CDVR to maintain frequency of generator and load. The droop CT is used for quadrature compensation, and is used for proper sharing of reactive power between parallel connected generators.
4.3.15 Generator Bus Terminal


       Bus terminal
Figure 4.3.15: Bus terminal
The generator bus terminal is used to share the generating voltage from main alternator to the load. It is a super conductor. It helps the generator to pass the voltage without any loss of voltage.
4.4 Generation System

Rotating part


KVA Output
Stationary part
Figure 4.4: Power Generation
To generate power the caterpillar generator follows the following steps:
Excitation part
Step 1
The CDVR takes the power from the external 24 volt battery. Then it passes the voltage to exciter 8 pole field coil to produce the electro- magnetic field. A voltage regulator maintains the terminal voltage of an alternator or generator at a predetermined value. Voltage is controlled by regulating the strength of the electromagnetic field produced in the alternator exciter. A voltage regulator automatically overcomes voltage drop within the alternator by changing field excitation automatically as it varies with the load.
Step 2
The electric fields produced by exciter field coil cut by 3 phase the rotating exciter armature coil. In these steps, the exciter produces 36 ac voltage as it is the excitation voltage.
AC to DC converting part
Step 3
The rotating rectifier group takes 36 ac voltages as input and converts it to 36 dc voltage as output.
Main Alternator part                          
Step 4
This 36 dc voltage act on rotating main alternator field coil to produce the electro- magnetic fields.
Step 5
This rotating electro- magnetic field cut by the main alternator armature coil and produces 600 ac desired voltage.
Terminal part
These 3 phase 600 ac voltage comes to the generator bus bar terminal and exit the generator by T1, T2, T3 terminals.
The main generator output voltage should be kept at a constant value for whatever load conditions it may be supporting. The CDVR controls this function by controlling the output of the exciter.

5.1  Fault No.01: Voltage Problem
  Ø  Check all connection
  Ø  Check CDVR by ET
  Ø  Check Mega Test and found reading as bellow:
             Main rotor: 48GΩ
             Main stator: 102 MΩ 
             Exciter rotor: 53 GΩ
             Exciter stator: 22GΩ
Cause: Rectifier burned
Solution: Need to change Rectifier Group
                                                                                                               Figure 5.1: Mega Test
5.2 Fault No. 02: PO bus bar alarm
    Ø  Check all connection
    Ø  Check CDVR by ET
    Ø  Check PT connection
    Ø  Check generator skid
    Ø  We check bus bar line voltage divider
Cause: Bus bar line voltage divider damaged
Solution: Need to changed Bus bar line voltage divider
5.3 Fault No. 03: PO bus bar alarm                      
    Ø  Check all connection
    Ø  Check CDVR by ET
    Ø  Check PT connection
    Ø  Check generator skid
    Ø  Check bus bar line voltage divider
    Ø  Check CDVR breaker

Cause: CDVR breaker damaged
Solution: Replace CDVR breaker                                         
5.4 Fault No. 04: Generator Voltage Problem      
    Ø  Check all connection
    Ø  Checked rectifier group
    Ø  Check CDVR by ET
    Ø  Check PT connection
    Ø  Check generator skid
    Ø  Check bus bar line voltage divider                            Figure 5.4: Generator Skid Check
    Ø  Check CDVR breaker
Cause: PT connecting wire lose
Solution: Replace CDVR breaker                                 
5.5 Other types of Troubleshooting:
1.  On 22 September 2011, circuit breaker of a Ring machine was not working due to spring was damaged. As a result, Ring machine was not running. Then, we removed the damaged circuit breaker and replaced a new one.
2. On 25 September 2011, cooling fan of an inverter of 16 no Ring machine was damaged. As a result of that, temperature increased which cased machine to stop. We changed the cooling fan and run the machine again.
3. On 39 September 2011, cooling motor of a generator was burnt out. We removed the   damaged motor and replace it with extra motor.
4. On 12 October 2011, engine of a generator was misfiring. We checked spark plug and changed it.
5. On 18 October 2011, one of the drum of an Auto cone machine was not running. We checked the fault and found out that there is no power in drum circuit. Then, we checked the fuse with the millimeters and found it damaged. Therefore, we changed the fuse and finally been able to run the drum.
6. On 2 November 2011,Unifloc (A11) machine in blow room section stopped operation by showing message,” Collision Protection Rear 300”. We checked the machine and found door sensor was displaced. Then, we adjusted sensor and run the machine.
7. On 16 November 2011, the Unimix machine was stopped. Then, we went down there and. checked the monitor of Unimix machine and found limit switch B32 is open. Then we identified B32 Limit switch and checked it with meter. We found out that, limit switch was damaged. Then, we removed the damaged limit switch with a new one and put machine into operation again.
8. On 24 November 2011, Overhead suction of a ring machine was not working. We checked overhead and found problem in carbon. Then, changed carbon and run the machine again.
9. On 4 December 2011, in Ring section, driving shaft motor of 9 no. Ring machine was making noise. We checked the motor and found bearing jam. Then, we changed bearing and measured ampere on running condition as follows(R-32, Y-31, and B-31) and machine was running smoothly.
On-site engine/generator sets (gensets) are used in a variety of applications. They are becoming more popular for load management applications since the deregulation and privatization of the utility industry. Some gensets are used strictly as “back-up” for emergencies and some as the only power source.
In Bangladesh, approximately 45% power is produced from different types of Caterpillar generator. For the massive use of Caterpillars generator in Bangladesh as well in the whole world, it is very much important to know about the generator set and its basic components. It is also very much important to operate this gen set safely and perfectly. Only by this method, we can get proper output from Caterpillar generator and we can minimize the cost of spare parts.
Caterpillar’s well-proven, innovative generator designs have lead to several highly reliable lines of generators used in electric power generation applications worldwide. From offshore oilrigs to natural diesel fields, from remote areas to urban confines wherever there’s a need for clean, efficient, reliable power there’s a Caterpillar generator.
This report is designed to provide the basic concepts involved in the Caterpillar Diesel generator.
Abbreviation               Elaboration
AC                                            Alternating Current
BDC                                         Bottom Dead Centre
DC                                            Direct Current
C                                               Celsius
CAT                                         Caterpillar
CDVR                                       CAT Digital Voltage Regulator
CT                                            Current Transformer
DVR                                         Digital Voltage Regulator
ECU                                          Engine Control Unit
ECM                                         Engine Control Module
EMF                                          Electro Magnetic Field
EPG                                          Electric Power Generation
EPTC                                        Electronic Programmable Transmission Control
ET                                             Electric Technician
EUI                                           Electronic Unit Injection
F                                               Fahrenheit
Gen                                           Generator
Hz                                             Hertz
Abbreviation               Elaboration
KVA                                         Kilo Volt Ampere
KW                                           Kilo Watt
KWH                                        Kilo Watt Hour
PT                                             Potential Transformer
rad                                            Radian
RPM                                         Rotation per Minute
RTDs                                        Resistance Temperature Detectors
TDC                                          Top Dead Centre
Temp                                        Temperature
V                                              volt
VAC                                         Variable Alternating Current
VDC                                         Variable Direct Current
VIMS                                        Vital Information Management System

  1. http:// www.cat-engines.com
  2. http://en.wikipedia.org/wiki/Engine_control_unit
  3. J.N. Sarker A Text Book Of Diesel Engine. 22nd July, 1964
  4. Van Valkenburgh, Nooger, and Neville, Basic Electricity, Vol. 5, Hayden Book Company.
  5. Lister, Eugene C., Electric Circuits and Machines, 5th Edition, McGraw-Hill.
  6. Kidwell, Walter, Electrical Instruments and Measurements, McGraw-Hill.
  7. Ast, D. G. (1984) Semiconductors and Semimetals, Vol. 21, p. 115. (Eds. R. K. Willardson, and A. C. Beer), Academic Press, New York.
  8. Caterpillar 3500B user guide.