Diesel Generator Working Principle and Functions
A diesel generator is made of the diesel engine and electric generator to produce electrical energy. It is specifically designed to use diesel, but some types of generators use other fuels, gas or both (bi-fuel operation).
In most cases, diesel generators are used in places that are not connected to the power grid and sometimes as power back-up in case of outages.
The combination of the engine, electric generator and other components of the generator are referred to as the generating set or gen set.
Diesel generators exist in different sizes depending on the usage. For instance, for small applications such as homes and offices, they range from 8kW to 30Kw. In the case of large applications such as factories, the size varies from 80kW to 2000Kw.
How does a diesel generator create electricity
The diesel generator converts mechanical energy into electrical power. It is important to note that the generator does not create the electrical energy but instead acts as a channel of electrical charges. It works similarly to the water pump that only allows water to pass through.
i. The engine
The engine part of the generator is similar to the vehicle engine and acts as the source of the mechanical energy. The maximum power output a generator can produce is directly related to the size of the engine.
ii. The alternator
This is the component of the diesel generator that converts the mechanical energy into electrical energy. The working principle of the alternator is similar to the process described by Michael Faraday in the nineteenth century.
The principle holds that an electric current is induced in an electrical conductor when passed through a magnetic field. This process causes electrons to flow through the electrical conductor.
The amount of the current produced is directly proportional to the strength of the magnetic fields. There are two main components of the alternator working together to cause the movements between the conductors and magnetic fields to produce electrical energy;
(a) Stator- It contains coils of electrical conductor wounded on an iron core
(b) Rotor –It produces magnetic fields around the stator inducing voltage difference that generates alternating current (A/C).
There several factors that you should consider while determining the alternator, including:
(a) Housing- Metal casing is more durable than the plastic casing.
Besides, plastic casing gets deformed and may expose the components increasing wear and tear and risk to the user.
(b) Bearings- Ball bearings last longer than needle bearings.
(c) Brushes- Brushless designs produce clean energy and are easier to maintain than those that contain brushes.
iii. The fuel system
The fuel tank should be sufficient enough to hold fuel for between six to eight hours of operation.
For small or portable units, the tank is part of the generator and externally erected for large generators. However, installation of external tanks requires necessary approvals. The fuel system contains the following components;
(a) Supply pipe- This is the pipe that connects the fuel tank to the engine.
(b) Ventilation pipe- The ventilation pipe prevents pressure and vacuum from building up when refilling or draining the tank.
(c) Overflow pipe- this pipe prevents spillage of the fuel on the generator set during refilling.
(d) Pump- It transfer the fuel from the storage tank to operational tank
(e) Fuel filter- The filter separates the fuel from water and other materials that cause corrosion or contamination
(f) Injector- sprays fuel to the cylinder where combustion takes place.
iv. Voltage regulator
The voltage regulator is an essential component of the generator because it controls the output voltage. In fact, the regulation of voltage is a complicated cyclical process that ensures the output voltage is equivalent to the operating capacity.
Nowadays, most electrical devices rely on a steady power supply. Without the regulator, the electrical energy will not be stable due to the varying engine speed.
v. The cooling and exhaust system
(a) Cooling system
Apart from the mechanical energy, the generator also produces a lot of heat. A cooling and ventilation systems are used to withdraw the excessive heat.
There are different types of coolants used for diesel generators depending on the application. For instance, water is sometimes used for small generators or huge generators that exceed 2250kW.
However, hydrogen is commonly used in most generators since it absorbs heat more efficiently than other coolants. Standard radiators and fans are sometimes used as the cooling systems especially in residential applications.
In addition, it is advisable to place the generator in a sufficiently ventilated area to ensure adequate supply of cooling air.
(b) Exhaust system
Similar to the vehicle engine, the diesel generator emits harmful chemicals such as carbon monoxide that should be managed efficiently. The exhaust system ensures that the toxic gases produced are appropriately disposed of.
In most cases, the exhaust pipes are made of steel, cast and wrought iron and are not attached to the engine to minimize vibrations.
vi. Lubricating system
The generator involves moving parts that require lubrication for smooth operations and durability. The oil pump and reservoir attached to the engine automatically applies the oil. It is prudent to check the level of the oil after every eight hours of operations and also for any leakages.
vii. The battery charger
The diesel generator relies on a battery to start running. Stainless steel chargers ensure the battery is adequately charged with float voltage from the generator. The mechanism is fully automated and does not require manual adjustments.
viii. The control panel
This is the user interface where the generator is controlled and operated, and the features vary with the manufacturers. Some of the standard features include;
(a) On/off button- The start button can either be manual, automatic or both. An auto start control automatically starts the running of the generator when there is an outage or shut down operations when not in use
(b) Engine gauges- Display various parameters such as the temperature of the coolant, rotation speed, etc.
(c) Generator gauges- Shows the measurement of the current, voltage and operating frequency
ix. Assembly frame
All generators contain waterproof casing that keeps all the components together provides safety and structural support. To conclude, the diesel generator converts mechanical energy to electrical power by electromagnetic induction rule.