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ConfigurationWhen selecting diesel generators, the first question is how much is the load it is going to supply and what is amount of both running loads and starting loads. This is known as Sizing. The second question is the generator going to run as standby for the mains or it is going to run as prime power. The third question is for how long is this investment is going to last?. In other words are we going to select a heavy duty genset to last 10 years or more or it is going to be for short temporary application. Where the genset is going to be installed and under which environmental conditions. All these considerations affect the final decision of which diesel engine prime over is going to be and which alternator is going to be driven and what is the KW rating of this genset and how it will be installed,...etc. Click to learn more and earn a certificate!. SizingAs part of configuration process of a genset is to answer the question: What is the size of this genset in terms of KW rating and what is its reactive capability to withstand the transient loads. The sizing process is started always by sizing the site load and defining the total running and starting KW or KVA and then apply the other site load criteria such as maximum allowable voltage dip, load factor and the future expansion to calculate the size of the generator(s). Click to learn more and earn a certificate!. DesignWhat are the different equipment and components which all together make the genset and how they are put together as one system to give the required genset with its pre-defined specifications. This is the design process. Genset manufacturers or packagers don't usually assemble the major equipment as per the configuration and design drawings. Some manufacturers design some or all of the genset supporting systems such as the skid bases, control panels, circuit breaker panels, exhaust system, fuel tanks, weather enclosures,....etc for which these manufacturers should have engineering design office and produce shop floor drawings and bills of materials. Click to learn more and earn a certificate! ManufacturingThe manufacturing process starts from receiving the design drawings and materials including the major equipment (engine and alternator). The manufacturing process differs fro one manufacturer to another. While some manufacturers do everything or most of the work in house, some manufacturers outsource most of the work to more specialized manufacturers such as steel work for skid bases, fuel tanks and weather enclosures. Some manufacturers even outsource the control panels and switchgear and what they do is just assemble and test. Click to learn more and earn a certificate! Diesel Engine
The diesel engine is the most important part
of the genset. It is the prime mover which drives the generator
(alternator) to produce electricity.
AC Generator (Alternator)
The ac generator or alternator is the second
major part of the genset. Nowadays most if not all of the
alternators are brushless type with rotating excitation system. The
alternator is selected during the configuration process.
Speed Governing
The two main parameters we must control in the
diesel generator sets are speed and voltage. Controlling the speed
is controlling the diesel engine prime mover via controlling the
fuel while controlling the voltage is controlling the AC generator
(alternator) via controlling the excitation of the rotor
(magnetization of the rotor). Speed governing or control like any
other en control consists of sensing part which measure the running
speed of the diesel engine (using magnetic pickups).
Excitation ControlsAs mentioned elsewhere the excitation is simply magnetizing the rotor to produce magnetic field. During the rotation of the rotor this field flux lines will intersect with the stator windings and electromotive force (emf) will be generated accordingly. Most of the alternators used nowadays are brushless type, where the DC current required to magnetize the rotor is produced by the exciter generator and then rectified by the rotating rectifiers. To control the amount of excitation we need to control the exciter generator. The voltage regulator is used to sense the output voltage of the alternator and then compares it with the setting to produce the error. This error is amplified and modulated to control the field of the exciter. Click to learn more! Engine Auxiliary Systems and InstrumentationEach genset has auxiliary systems to support its functions. Most if not all of these systems are attached to the diesel engine. Cooling system, fuel system, lubrication system, air intake system, exhaust system. each one of these systems can vary in the design specs even for the same engine, this is depending on the application and configuration of the genset. Each of these systems has instrumentation to measure and indicate the operating parameters. Click to learn more and earn a certificate!. Safeties and ProtectionThe genset consists of mechanical part represented by the diesel engine and electrical part represented by the AC generator (alternator). Each of these two major equipment must be properly protected against abnormal operating parameters. There are of course mechanical parameters and electrical parameters. For example the oil pressure and water temperature are two of the mechanical parameters while the AC current and voltage are two of the electrical parameters which we must protect the genset against abnormal values. Click to learn more about genset protection and earn a certificate. Control SystemEach genset must have a control system, The control system consists of sensors and actuators connected to a control panel. The control panel normally has a controller which does the start and stop of the genset and protect the genset against abnormal operating parameters. The control panel can have lot of optional controls, protection and metering devices as per the design to suit the applications and configuration of the genset to meet customer's specs. Click to learn more about control systems and earn a certificate. Switchgear and Power DistributionThe switchgear is the electrical part of the genset which connects and disconnect the genset output electrical power to the load. The switchgear is usually a circuit breaker or a contactor. Click here to learn more and earn a certificate. Testing Diesel GeneratorsEach manufactured diesel generator set is normally tested at the factory according to the application and configuration of the genset and following a design criteria. The purpose of the factory test is to validate the genset design to meet the specified criteria. This includes functional test, load test and safeties and protections test. Click here to learn more and earn a certificate. Trouble-shooting Diesel GeneratorsWhen diesel generator sets operate, whether in standby mode or as prime power they are expected to encounter some mechanical or electrical problems which could cause them to either shutdown or their performance to degrade. Genset problems vary from simple electrical wiring faults to major engine problems. Trouble-shooting the problems in the gensets is simply answering the question: what caused this alarm, or what caused this shutdown or what caused this erratic behavior. Trouble-shooting is a process starting with collecting the information then defining the problem. After defining the problem list all the possible causes of the problem and finally select the solution or solutions which eliminate the problem or problems taking into consideration the economics and reliability. Click to learn more and earn a certificate! Vibration on Diesel GeneratorsDiesel generator sets can suffer from excessive vibration which could cause failures and unwanted noise. Vibration can be linear or no linear. Sources of linear vibration can come from diesel engine internal combustion forces, miss alignment, unbalanced mounting and structural resonance. Nonlinear vibration can be caused from the shaft torsional forces. To control vibration we need to define its parameters, then we need to measure them and know the relationship between them and then we control them. Vibration main parameters are displacement, velocity, acceleration and frequency. These 4 parameters are related to each other mathematically. Another parameter which is necessary for analyzing the vibration and establishing its source is the vibration order. Click to learn more and earn a certificate! Paralleling and Load Sharing Diesel Generatorsbased on the results of the load sizing we may need to have more than one genset to operate in parallel to supply the load. When gensets operate in parallel they encounter problems not seen when they operate standalone. Some of these problems is how maintain the frequency of the system, how to share the site load, how to eliminate the reactive cross current and how to control the start and stop of these gensets when the site load increase or decrease and which genset will be the duty genset and which ones will be the non-duty and so on. These challenges require installing paralleling and load sharing control system with load demand control. To better understand this system we need to know for example the two modes of paralleling (droop and isochronous) and if the gensets are going to be paralleled with each other or with the mains and so on. Click to learn more and earn a certificate! Installation of Diesel GeneratorsDiesel generators can be as small as 10 KW and can be big to exceed 10000 KW. When these gensets are to be installed at the site there are lot of considerations to be taken. Gensets could be as heavy as 50 Ton or more. These need concrete foundations to be mounted on. They breath air for combustion so fresh filtered air must be brought to them. Gensets need enough space so engine rooms must be designed to suit them. gensets require ventilation to reject the heat outside the engine rooms so inlet and outlet openings are to be integrated within the engine room design. Exhaust pipes need to be extended to outside the engine room, this has to be also taken into consideration. Ducts for power cables, control cables, fuel and coolant pipes could be needed and many more. Click to learn more and earn a certificate!. Automatic Transfer SwitchWhen the diesel generator is used as standby for the mains power then it requires automatic transfer switchgear to transfer the load automatically from the mains power to the standby generator when the mains power fails. The ATS can be made or purchased in different styles. The open transition ATS is the most common one where it transfers the power from normal source to emergency source. The other style is the open transition bypass isolation ATS. This is similar to the first one except the ATS module can be completely isolated from the circuit when it malfunctions and two bypass switches are used to bypass either the normal power or the emergency power. The third famous style is the closed transition ATS. The difference between open and closed transition is that in the open transition the normal side switch opens before the emergency side switch is closed (break before make), while in the closed transition types the emergency side closes before the normal side opens (make before break). Other styles are also available. Click to learn more and earn a certificate!
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All diesel engines are similar
to each other in the concept but they differ in the number of
cylinders, if the cylinders are line or V-type, how the fuel is
delivered to the cylinders, governing system and other auxiliary
systems which are attached to the engines such as pre-lube oil
pumps, turbochargers and others systems. All these details affect
the decision of which engine to use and which performance is
expected. Please 
It should
be matched mechanically to the diesel engine. Electrically the
alternator should be selected to provide the required KW at the
specified voltage, frequency, ambient temperature, altitude and it
should be capable to withstand the transient loads without exceeding
the maximum allowable voltage dips.
The speed is
then speed controller compares the actual running speed with the set
point and produce an error. This error is then amplified and
converted to an output signal going to the actuator which controls
the opening and closing of the fuel valve to increase or decrease
the speed of the diesel engine. This speed governing system is
electronic type. Governors can also be mechanical hydraulic type.
