File Name: construction and working principle of diesel generator .zip
Alternators or synchronous generators can be classified in many ways depending upon their application and design. According to application these machines are classified as-.
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- What is a diesel generator? How does it work?
- What are the main component parts of a diesel generator?
This article is for the design, materials, manufacture, testing, and commissioning of packaged stand-by diesel engine generators intended for permanent installation in industrial plants. Self-contained enclosure shall be provided for the diesel generator set. The enclosure shall be manufactured such that all part are accessible for inspection and minor maintenance without removal of the enclosure or enclosure roof.
The diesel engine is the workhorse in the generator. It burns diesel fuel, to create rotary motion which is used to turn the AC alternator. The AC alternator turns the rotary motion from the engine into electricity, which is used to power the generators load. On a generator with a water cooled diesel engine, you will see a radiator.
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A diesel generator DG also known as diesel genset is the combination of a diesel engine with an electric generator often an alternator to generate electrical energy. This is a specific case of engine-generator. A diesel compression-ignition engine is usually designed to run on diesel fuel , but some types are adapted for other liquid fuels or natural gas. Diesel generating sets are used in places without connection to a power grid , or as emergency power-supply if the grid fails, as well as for more complex applications such as peak-lopping, grid support and export to the power grid.
Proper sizing of diesel generators is critical to avoid low-load or a shortage of power. Sizing is complicated by the characteristics of modern electronics , specifically non-linear loads. In size ranges around 50 MW and above, an open cycle gas turbine is more efficient at full load than an array of diesel engines, and far more compact, with comparable capital costs; but for regular part-loading, even at these power levels, diesel arrays are sometimes preferred to open cycle gas turbines, due to their superior efficiencies.
The packaged combination of a diesel engine , a generator and various ancillary devices such as base, canopy, sound attenuation, control systems , circuit breakers , jacket water heaters and starting system is referred to as a "generating set" or a "genset" for short. A combination of these modules are used for small power stations and these may use from one to 20 units per power section and these sections can be combined to involve hundreds of power modules.
In these larger sizes the power module engine and generator are brought to site on trailers separately and are connected together with large cables and a control cable to form a complete synchronized power plant. A number of options also exist to tailor specific needs, including control panels for autostart and mains paralleling, acoustic canopies for fixed or mobile applications, ventilation equipment, fuel supply systems, exhaust systems, etc.
Diesel generators are not only for emergency power, but may also have a secondary function of feeding power to utility grids either during peak periods, or periods when there is a shortage of large power generators. Ships often also employ diesel generators, sometimes not only to provide auxiliary power for lights, fans, winches etc. With electric propulsion the generators can be placed in a convenient position, to allow more cargo to be carried. Electric drives for ships were developed before World War I.
Electric drives were specified in many warships built during World War II because manufacturing capacity for large reduction gears was in short supply, compared to capacity for manufacture of electrical equipment.
Generating sets are selected based on the electrical load they are intended to supply, the electrical load's characteristics such as kW , kVA , var , harmonic content , surge currents e. The expected duty such as emergency, prime or continuous power as well as environmental conditions such as altitude , temperature and exhaust emissions regulations must also be considered.
Most of the larger generator set manufacturers offer software that will perform the complicated sizing calculations by simply inputting site conditions and connected electrical load characteristics. One or more diesel generators operating without a connection to an electrical grid are referred to as operating in island mode. Operating generators in parallel provides the advantage of redundancy, and can provide better efficiency at partial loads.
The plant brings generator sets online and takes them off line depending on the demands of the system at a given time. An islanded power plant intended for primary power source of an isolated community will often have at least three diesel generators, any two of which are rated to carry the required load. Groups of up to 20 are not uncommon. Generators can be electrically connected together through the process of synchronization.
Synchronization involves matching voltage , frequency and phase before connecting the generator to the system. Failure to synchronize before connection could cause a high short circuit current or wear and tear on the generator or its switchgear. The synchronization process can be done automatically by an auto-synchronizer module, or manually by the instructed operator.
The auto-synchronizer will read the voltage, frequency and phase parameters from the generator and busbar voltages, while regulating the speed through the engine governor or ECM Engine Control Module. Load can be shared among parallel running generators through load sharing. Load sharing can be achieved by using droop speed control controlled by the frequency at the generator, while it constantly adjusts the engine fuel control to shift load to and from the remaining power sources.
A diesel generator will take more load when the fuel supply to its combustion system is increased, while load is released if fuel supply is decreased. In addition to their well known role as power supplies during power failures, diesel generator sets also routinely support main power grids worldwide in two distinct ways:.
Emergency standby diesel generators, such as those used in hospitals and water plants, are, as a secondary function, widely used in the US and, in the recent past, in Great Britain to support the respective national grids at times for a variety of reasons. In the UK the tenders known as the Short Term Operating Reserve have exhibited quite variable prices, and from the volume of demand-side participation, which mainly entails the use of on-site diesels, has dropped as the tendered prices fell.
Some 0. This is beneficial for both parties - the diesels have already been purchased for other reasons; but to be reliable need to be fully load tested.
Grid paralleling is a convenient way of doing this. This method of operation is normally undertaken by a third party aggregator who manages the operation of the generators and the interaction with the system operator. These diesels can in some cases be up and running in parallel as quickly as two minutes, with no impact on the site the office or factory need not shut down.
This is far quicker than a base load power station which can take 12 hours from cold, and faster than a gas turbine, which can take several minutes. Whilst diesels are very expensive in fuel terms, they are only used a few hundred hours per year in this duty, and their availability can prevent the need for base load station running inefficiently at part load continuously.
The diesel fuel used is fuel that would have been used in testing anyway. National Grid does not control these diesels - they are run by the customer to avoid "triad" transmission network use of system TNUoS charges which are levied only on consumption of each site, at the three half-hours of peak national demand.
It is not known in advance when the three half-hours of peak national demand the "triad" periods will be, so the customer must run his diesels for a good deal more half-hours a year than just three.
Most plant is for large offices blocks, hospitals, supermarkets, and various installations where continuous power is important such as airports. Therefore, most is in urban areas, particularly city and commercial centres. Although it is growing, only a very small proportion is believed to be used regularly for peak lopping, the vast majority just being only for standby generation.
The information in this paragraph is sourced from section 6. Increasing use of banks of diesel generators known as "diesel farms" is being made in Britain to balance the fluctuating output from renewable energy sources, such as wind farms. In this case, the diesels prime function is to feed power into the grid. During normal operation in synchronization with the electricity net, powerplants are governed with a five percent droop speed control.
This is required for the stable operation of the net without hunting and dropouts of power plants. Normally the changes in speed are minor. Adjustments in power output are made by slowly raising the droop curve by increasing the spring pressure on a centrifugal governor. Generally this is a basic system requirement for all powerplants because the older and newer plants have to be compatible in response to the instantaneous changes in frequency without depending on outside communication.
Fuel consumption is the major portion of diesel plant owning and operating cost for power applications, whereas capital cost is the primary concern for backup generators. Generators must provide the anticipated power required reliably and without damage and this is achieved by the manufacturer giving one or more ratings to a specific generator set model. A specific model of a generator operated as a standby generator may only need to operate for a few hours per year, but the same model operated as a prime power generator must operate continuously.
When running, the standby generator may be operated with a specified - e. The same model generator will carry a higher rating for standby service than it will for continuous duty. Manufacturers give each set a rating based on internationally agreed definitions. These standard rating definitions are designed to allow valid comparisons among manufacturers, to prevent manufacturers from misrating their machines, and to guide designers. Standby Rating based on Applicable for supplying emergency power for the duration of normal power interruption.
No sustained overload capability is available for this rating. Nominally rated. Typical application - emergency power plant in hospitals, offices, factories etc.
Not connected to grid. Output available with varying load for an unlimited time. This rating is not applicable to all generator set models. Typical application - where the generator is the sole source of power for say a remote mining or construction site, fairground, festival etc. Base Load Continuous Rating based on: Applicable for supplying power continuously to a constant load up to the full output rating for unlimited hours.
Consult authorized distributor for rating. However these ratings vary according to manufacturer and should be taken from the manufacturer's data sheet.
Often a set might be given all three ratings stamped on the data plate, but sometimes it may have only a standby rating, or only a prime rating.
Typically however it is the size of the maximum load that has to be connected and the acceptable maximum voltage drop which determines the set size, not the ratings themselves. If the set is required to start motors, then the set will have to be at least three times the largest motor, which is normally started first. This means it will be unlikely to operate at anywhere near the ratings of the chosen set. Many gen-set manufacturers have software programs that enable the correct choice of set for any given load combination.
Sizing is based on site conditions and the type of appliances, equipment, and devices that will be powered by the generator set. Diesel fuel is named after diesel engines, and not vice versa; diesel engines are simply compression-ignition engines, and can operate on a variety of different fuels, depending on configuration and location. Where a gas grid connection is available, gas is often used, as the gas grid will remain pressurized during almost all power cuts.
This is implemented by introducing gas with the intake air and using a small amount of diesel fuel for ignition. In more rural situations, or for low load factor plant, diesel fuel derived from crude oil is a common fuel; it is less likely to freeze than heavier oils. Endurance will be limited by tank size. Diesel engines can work with the full spectrum of crude oil distillates, from natural gas, alcohols, gasoline, wood gas to the fuel oils from diesel oil to cheaper residual fuels that are like lard at room temperature, and must be heated to enable them to flow down a fuel line.
Larger engines from about 3 MWe to 30 MWe sometimes use heavy oils, essentially tars, derived from the end of the refining process.
The slight added complexity of keeping the fuel oil heated to enable it to flow, whilst mitigating the fire risks that come from over-heating fuel, make these fuels unpopular for smaller, often unmanned, generating stations. Other possible fuels include: biodiesel , straight vegetable oil , animal fats and tallows , glycerine , and coal-water slurry. These should be used with caution and due to the composistion, normally have a detrimental effect on engine life.
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What is a diesel generator? How does it work?
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A diesel generator DG also known as diesel genset is the combination of a diesel engine with an electric generator often an alternator to generate electrical energy. This is a specific case of engine-generator. A diesel compression-ignition engine is usually designed to run on diesel fuel , but some types are adapted for other liquid fuels or natural gas. Diesel generating sets are used in places without connection to a power grid , or as emergency power-supply if the grid fails, as well as for more complex applications such as peak-lopping, grid support and export to the power grid. Proper sizing of diesel generators is critical to avoid low-load or a shortage of power. Sizing is complicated by the characteristics of modern electronics , specifically non-linear loads.
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What are the main component parts of a diesel generator?
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