An electrical device that generates electrical energy is called a DC generator. The primary function of this device is to convert mechanical energy to electrical energy. A generator provides power to each electrical power grid. The electric motor helps in the reverse function of the generator. Motors are similar to generators in function and feature.
We will learn a bit about DC generators and the main difference between AC and DC industrial generators.
DC generator:
A direct current generator (DC) is an electric machine to convert mechanical energy into DC electricity. Induced electromotive force is the process of energy alteration. The DC generator diagram is shown below.
Parts of a DC generator:
A DC generator also called a DC machine, has a 4 pole construction. There are many parts in the DC machine such as armature winding, field winding, an armature core, commutator, yoke, brushes, poles and pole shoes. To critical parts are the stator and rotor.
Stator
The main function of the stator is to provide magnetic fields where the coil spins. This is an essential segment in the DC machine. It includes stables magnets with reverse poles facing—the magnets fit in the location of the rotor.
Rotor
This is the second most important part called the rotor, also known as armature core. It is the rotating part of the DC machine, which includes slotted iron laminations with slots and is stacked in a pattern to construct the shape of a cylindrical armature core. Due to loss because of the eddy current, these laminations help reduce the loss. The armature forms the centre of electromechanical conversion.
Armature windings
The armature core mentioned above helps hold the copper armature windings. These are wound in a closed circuit, and it is connected to enhance the current produced. Each conductor in the winding is insulated, which comes in two types – lap winding and wave winding.
Yoke
The external body of the DC generator is called the yoke made of outcast iron or steel. It helps carry the magnetic flux through the poles. Its two important functional roles are to provide a path for pole flux and provide mechanical power to the whole machine.
Poles
Poles support the field windings. The winding is wound around these poles, which are connected in series and are parallel to armature windings.
Pole shoes
Pole shoe distributes the flux in the air gap uniformly to avoid the field coil from failing.
Commutator
A commutator, alternatively called a mechanical rectifier, helps switch AC voltage to DC voltage with the armature across the brushes. It is designed with hard drawn copper segments protected with a coat of mica sheets forming a ring structure. It is placed at the shaft of the machine. The commutator collects the current generated in the armature winding.
Brushes
Brushes ensure proper electrical connection and are placed over the commutator. Its main function is to collect current from the commutator and supply it to the electrical circuit or electrical load.
DC generator working principle
A DC generator uses the principle of Faraday’s Laws called electromagnetic induction, where energetically induced electromotive force is generated. This electromotive force (EMF) causes the current to flow. The magnitude of induced EMF is directly proportional to the rate of change of flux linkage. The conductor present in the closed lane will flow in the lane. This path of induced current will be provided by Fleming’s right-hand rule.
EMF equation of DC generator is Eg = PØZN/60 A
Where,
Ø is flux or pole with Webber
Z is the total number of armature conduct
P is the number of poles in a generator
A is the number of parallel lanes with the armature
N is the rotation of armature in the revolutions per minute (rpm)
E is induced EMF
Eg is generated EMF
N/60 is the number of turns per second
AC generator
The (Alternating Current) AC motor is generated from the principle of magnetism. In its working, a permanent magnet rotor moves between two electromagnetic stator poles with a fine air gap between them. These electromagnets are directly connected to a source of AC supply which get energised and form magnetic poles.
Difference between AC and DC generators
| AC generator | DC generator |
| 1. AC generator is a mechanical device converting mechanical energy into AC electrical energy. | 1. DC generator is a mechanical device converting mechanical energy into DC electrical energy. |
| 2. The flow of electrical current reverses its direction periodically. | 2. The flow of electrical current is only in one direction. |
| 3. The coil through which the current flows is fixed while the current moves. | 3. The coil through which the current flows rotates in a fixed field. |
| 4. It has a simple construction and is inexpensive. | 4. Though the design is simple, the construction is complex due to commutators and slip rings. |
| 5. It does not have commutators. | 5. It has commutators for the current to flow in one direction. |
| 6. AC generators have slip rings. | 6. DC generators split-ring commutators |
| 7. It is used to power small electrical appliances. | 7. It is used to power large motors. |
| 8. Require less maintenance. | 8. Require frequent maintenance. |
| 9. Safe to travel long distances, like intercity and can provide more power. | 9. It cannot travel long distances because it tends to lose power. |
Conclusion
These were the main parts of a DC generator, along with some general information on them. So, now that you know about DC generators, why not learn more about AC generators?
