What is a DC Generator? Construction, Working Principle, and Applications

The initial electromagnetic generator (Faraday disk) was invented by British scientist namely Michael Faraday in the year 1831. A DC generator is an electrical device used for generating electrical energy. The main function of this device is to change mechanical energy into electrical energy. There are several types of mechanical energy sources available such as hand cranks, internal combustion engines, water turbines, gas and steam turbines. Generator provides power to all the electrical power grids. The reverse function of the generator can be done by an electric motor. The main function of the motor is to convert electrical energy to mechanical. Motors, as well as generators, have similar features. This article discusses an overview of DC generators.

What is a DC Generator?

A DC generator or direct current generator is one kind of electrical machine, and the main function of this machine is to convert mechanical energy into DC (direct current) electricity. The energy alteration process uses the principle of energetically induced electromotive force. The dc generator diagram is shown below.

DC Generator
DC Generator

When a conductor slashes magnetic flux, then energetically induced electromotive force will be generated in it based on the Electromagnetic Induction principle of Faraday’s Laws. This electromotive force can cause a flow of current when the conductor circuit is not opened.

Construction of a DC Generator

A DC generator is also used as a DC motor by without changing its construction. Therefore, a DC motor otherwise a DC generator can be generally called as a DC machine. The construction of a 4-pole DC generator is shown below. This generator comprises of several parts like yoke, poles & pole shoes, field winding, an armature core, armature winding, commutator & brushes. But the two essential parts of this device are stator as well as the rotor.

Stator

The stator is an essential part of the DC generator, and the main function of this is to provide the magnetic fields where the coils spin. This includes stable magnets, where two of them are with reverse poles facing. These magnets are located to fit in the region of the rotor.

Rotor or Armature Core

Rotor or armature core is the second essential part of the DC generator, and it includes slotted iron laminations with slots that are stacked to shape a cylindrical armature core. Generally, these laminations are offered to decrease the loss because of the eddy current.

Armature Windings

The armature core slots are mainly used for holding the armature windings. These are in a closed circuit winding form, and it is connected in series to parallel for enhancing the sum of produced current.

Yoke

The external structure of the DC generator is Yoke, and it is made with cast iron otherwise steel. It gives the necessary mechanical power for carrying the magnetic-flux given through the poles.

Poles

These are mainly used to hold the field windings. Usually, these windings are wound on the poles, & they are connected in series otherwise parallel by the armature windings. In addition, the poles will give joint toward the yoke with the welding method otherwise by using screws.

Pole Shoe

The pole shoe is mainly utilized for spreading the magnetic flux as well as to avoid the field coil from falling.

Commutator

The working of the commutator is like a rectifier for changing AC voltage to the DC voltage within the armature winding to across the brushes. It is designed with a copper segment, and each copper segment is protected from each other with the help of mica sheets. It is located on the shaft of the machine.

Brushes

The electrical connections can be ensured between the commutator as well as the exterior load circuit with the help of brushes.

Working Principle of DC Generator

The DC generator working principle is based on Faraday’s laws of electromagnetic induction. When a conductor is located in an unstable magnetic field, an electromotive force gets induced within the conductor. The induced e.m.f magnitude can be measured from the equation of the electromotive force of a generator.

If the conductor is present with a closed lane, the current which is induced will flow in the lane. In this generator, field coils will generate an electromagnetic field as well as the armature conductors are turned into the field. Therefore, an electromagnetically induced electromotive force (e.m.f) will be generated within the armature conductors. The path of induced current will be provided by Fleming’s right-hand rule.

DC Generator E.M.F Equation

The emf equation of dc generator according to Faraday’s Laws of Electromagnetic Induction is Eg= PØZN/60 A

Where Φ is a flux or pole within Webber
Z is a total no.of armature conductor
P is a number of poles in a generator
A is a number of parallel lanes within the armature
N is the rotation of armature in r.p.m (revolutions per minute)
E is the induced e.m.f in any parallel lane within the armature
Eg is the generated e.m.f in any one of the parallel lanes
N/60 is the number of turns per second
Time for one turn will be dt = 60/N sec

Types of DC Generator

The classification of DC generators can be done in two most important categories namely separately excited as well as self-excited.

Types of DC Generators
Types of DC Generators

Separately Excited

In separately excited type, the field coils are strengthened from an autonomous exterior DC source.

Self Excited

In self-excited type, the field coils are strengthened from the generated current with the generator. The generation of first electromotive force will occur because of its outstanding magnetism within field poles.

The produced electromotive force will cause a fraction of current to supply in the field coils, therefore which will increase the field flux as well as electromotive force generation. Further, these types of dc generators can be classified into three types namely series wound, shunt wound, and compound wound.

  • In a series wound, both the field winding & armature winding are connected in series with each other.
  • In shunt wound, both the field winding & armature winding are connected in parallel with each other.
  • The compound winding is the blend of series winding & shunt winding.

Applications of DC Generators

The applications of different types of DC generator include the following.

  • The separately excited type DC generator is used for boosting as well as electroplating. It is used in power and lighting purpose using field regulator
  • The self-excited DC generator or shunt DC generator is used for power as well as ordinary lighting using the regulator. It can be used for battery lighting.
  • The series DC generator is used in arc lamps for lighting, stable current generator and booster.
  • Compound DC generator is used to provide the power supply for DC welding machines.
  • Level compound DC generator is used to provide a power supply for hostels, lodges, offices, etc.
  • Over compound, DC generator is used to reimburse the voltage drop within Feeders.

Thus, this is all about the DC generator. From the above information finally we can conclude that the main advantages of DC generator include simple construction & design, parallel operation is easy, and system stability problems are less not like the alternators. Here is a question for you, what are the disadvantages of DC generator?



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