Electric generator, also known as dynamos or alternators are machines that convert mechanical energy to electricity for transmission as well as distribution over power lines for domestic, industrial and commercial use.
The mechanical power for an electric generator is often got from a rotating shaft and is equal to the shaft torque multiplied by angular or rotational velocity.
The mechanical power usually comes from different sources like hydraulic turbines at waterfalls and dams, steam turbines, wind turbines, gas turbines as well as diesel and gasoline engines. Therefore, its construction, as well as speed, will tend to vary depending on the features and characteristics of the mechanical prime mover, example a steam turbine.
Parts of an Electric Generator
- Rotating Shaft-This is connected to a motor or propellers in water or wind generators
- Armature-It creates an electromagnetic induction by spinning inside the stator of the opposing magnetism
- Stator-A stationary magnetic field with large copper windings
- Bearings-These reduce friction caused by the rotation
- Field Windings-This is a coil that creates a magnetic field through which the current flows
- Commutator-A conductor through which electricity collects
- Brush Assembly-It rubs against the commutator that sends electrical current out
- Frame-The frame shields all the electrical and moving parts of the generator, keeping all moisture and dirt out
The Working Principle of an Electric Generator
When it comes to an electric generator, we have to rely on Faraday’s law of electromagnetic induction. The law states that when a conductor links with a changing flux, it will have an induced emf across it. The value of the induced emf across the conductor often depends on the rate of change of flux linkage with the conductor.
Therefore, when a conductor moves in a magnetic field, an emf is induced across the conductor. Thus, forming the basis on which every rotating electric generator works.
As for the direction of the induced emf in the conductor, you can use Fleming’s Right-Hand Rule to determine it. This rule states that if you take your right hand, stretch your thumb, first and second finger perpendicular to each, and align your thumb along the direction of motion of the conductor in the magnetic field, and first finger along the direction of the magnetic field then your second finger indicates the direction of emf in the conductor.
How Electric Generators Work?
The chemical energy that is stored in fuel is converted into mechanical energy of the rotating shaft by a prime mover like steam turbines or gas-combustion turbines. After which, electricity is produced from the rotational energy of the generator’s spinning shaft.
Practically, the magnetic field is induced by an electromagnet. It consists of field coils that are mounted on an iron core. It is the flow of the current in the field coils that eventually produces a magnetic field. The current can be acquired from the generators armature or another external source.
If the current is gotten from the generator’s armature, then the initial field is produced by residual magnetism in the electromagnet’s cores.
When the prime mover of the generator starts to spin the armature will operate at very feeble magnetic fields, thus producing very little emf. The emf then creates current inside the field of coils, which then increases the magnetic flux, in turn increasing the emf. This process will continue until the rated output voltage has been reached.
The generated power voltage then creates an electric current, which results in energy being distributed to the load. As a result, the kinetic energy that spins the magnetic field source is converted into electricity.
You should take note of the current that is flowing through the external load as it would create a magnetic field that opposes the change in the flux of the coil, making the coil to oppose the motion. Besides, the higher the load current the larger the force should be. This is to keep the rotor going, preventing any slowdown.
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Types of Electric Generator
The type of generating equipment they employ often classifies these types of generators and the electrical energy produced is always alternating current or direct current.
- Alternating or AC generators are often classified as either single-phase generators or polyphase. A polyphase often produces two or more alternating voltages, mostly 2, 3 or 6 phases.
On the other hand, a single-phase type of generator is limited to 25kW or less. It generates AC power at a specific consumption voltage.
- Direct current or DC generators are often classified as series, shunt, and compound-wound but most are compound-wound. Shunt generators are often of use as battery chargers and exciters for alternating current, AC generators. Series generator types are at times useful for streetlights.
Here is a look at five major types of electric generators classified according to the production of their field flux.
- Shunt Generators-The field flux here is derived by connecting the field circuit directly across the generator terminals.
- Separately Excited Generator-The field flux is derived from a separate power source that is independent of the generator.
- Series Generator-The field flux produced is got from connecting the field circuit in series with the generator¢s armature.
- Differentially Compound Generator-Here the shunt and series field flux is present but both their efforts are subtracted.
- Commutatively Compound Generator-In this type of generator both the series and shunt field flux are present and their efforts are a great additive.
Consequently, you can find electric generators by their different types of operation either for basic domestic use, industrial operation or as a backup generator.
Here are some which you can opt for, be it a propane generator, dual fuel generator or an inverter generator, depending on your needs.
- Mechanical Generators-These often uses mechanical energy to operate. They are most common in industrial sectors due to their superior energy transformation capacity. Besides, they are highly efficient and diversified.
- Chemical Generators-This type of generator is often responsible for converting chemical energy to electrical energy, for powering different kinds of equipment. A good example is a battery. They are often useful and used in equipment with low power consumption like clocks and radios.
- Thermal Generators-This often transforms thermal energy into They directly convert energy from heat and use it to create energy.
Solar Generators-This type is best at capturing solar energy and transforming it into electrical energy we can use. A great example of this type of generator is the solar silicon plates.