Explain Working Principles of DC Generator

Electrical generators are self-reliant pieces of machinery that provide electricity when there is no local grid power accessible. These generators provide companies and households with emergency power in the event of a power failure. 

Generators do not generate electrical energy but transform mechanical or chemical energy into electrical energy. Plenty of devices can be mechanically operated to produce electricity; often, they make sufficient manual generators.

The original electric generator, the Faraday disk, was built by British scientist Michael Faraday in 1831. The principle, called Faraday’s law, says that an electromotive force is produced in an electrical conductor surrounding a varying magnetic flux.

The output generators are categorised into two types, AC generators and DC generators. In this article, we will talk about Direct Current Generator in depth.

What Is a DC Generator?

A DC generator is an electrical machine whose fundamental purpose is to transform mechanical energy into electricity. When the conductor tears magnetic flux, an EMF will be produced based on the electromagnetic induction principle of Faraday’s Laws. This electromotive force can result in a wave of current when the conductor circuit is shut down.

 

Parts of a DC Generator

A DC generator can also be put into use as a DC motor without altering its structure. Thus, a DC motor, differently from a DC generator, can be commonly called a DC machine. The essential parts of a DC Generator are:

  • Stator

The primary purpose of the stator is to deliver magnetic fields where the coil curls. A stator contains two magnets with opposing polarities facing each other. These magnets are placed to adjust in the region of the rotor.

  • Rotor

A rotor in a DC machine contains slotted iron laminations with slots piled up to form a cylindrical armature core. The role of the nation is to reduce the loss inflicted.

  • Armature Windings

Armature windings are in a sealed circuit form and are attached in series to parallel to improve the generated current sum.

  • Yoke

Yoke is the outer structure of the DC generator. It is created of either cast iron or steel. It delivers the needed mechanical power for maintaining the magnetic flux provided through the poles.

  • Poles

The purpose of a pole is to keep up the field windings. These windings are wrapped on poles and are either attached in series or parallel by the armature windings.

  • Pole Shoe

Pole shoe is primarily used for stretching out the magnetic flux to prevent the field coil from collapsing.

  • Commutator

A commutator functions like a rectifier that alters AC voltage to DC voltage within the armature winding. It is constructed with a copper component, and each copper component is safeguarded from others with the support of mica sheets. It is placed on the shaft of the device.

  • Brushes

The electrical connections can be secured between the commutator and the external weight circuit with the aid of brushes.

How Does a DC Generator Work?

Following Faraday’s law of electromagnetic induction, we understand that when a current-carrying conductor is positioned in a varying magnetic space, an EMF is prompted in the conductor. According to Fleming’s right-hand rule, the path of the induced current shifts whenever the path of movement of the conductor shifts. 

Let us suppose an armature alternating clockwise and a conductor on the left is moving upwards. When the armature finishes off a half rotation, the path of movement of the conductor will be switched downward. Thus, the direction of the current in every armature will be rotating. But with a split ring commutator, connections of the armature conductors get switched when a current reversal takes place. Hence, we get an indirect current at the terminals.

E.M.F Equation For DC Generator 

The EMF equation for the DC generator is conveyed as:

E.g. = ϕZN /60  x P/A Volts  

Where,

E.g. – Produced EMF across any parallel route

P- Entire quantity of poles in the field

N- Rotational pace of armature(rpm)

Z- Total number of armature conductors in the field.

Ø- Magnetic flux produced per pole.

A- number of parallel paths in the armature.

E.g. = (PØNZ)/60A

Losses In a DC Generator

In a DC generator, the intake power is not entirely converted into the output power. Some portion of input power gets spent in distinct fashions. In a DC generator, the losses are largely classified into three types:

  • Copper Loss

Copper loss occurs when the current flows via the winding. These losses happen because of the opposition in the winding. The copper loss is classified into three phases: armature loss, field winding loss, and brush contact resistance loss.

  • Core Losses or Iron Losses

Few losses in the iron core take place when the armature rotates in the magnetic field. These losses are perceived as core losses. These losses are classified into two losses as Hysteresis loss and Eddy current loss.

  • Mechanical Losses-

Losses that transpire due to resistance between the components of the generator are named mechanical losses.

Types of DC Generators

The DC Generator can be divided into two different categories, i.e. Self-Excited and Separately-Excited.

Self Excited

In a Self-Excited sort, the field coils are stimulated from the produced current inside the generator. These kinds of generators can again be categorised into a sequence of wounds, shunt-wound, and compound wounds. Self-excited DC generators are arranged based on their field coils and their location:

  1. Shunt Wound Generators
  2. Compound Wound Generators
  3. Series Wound Generators

Separately Excited

In the case of a Separately-Excited type of generator, the field coils are driven by an external direct current source without restriction.

Applications of DC Generators

  • Field controllers use a Separately excited DC generator for power and lighting purposes. 
  • Arc lamps use the series DC Generator for reliable power generation, lighting and amplifier. 
  • Level Compound DC Generators are used to power homes, offices and accommodations. 
  • Compound DC generators are used to provide power to DC welding machines. 
  • A DC generator is used to compensate for the voltage drop on the feeders.

Conclusion

To conclude, we can certainly tell that the prime benefit of a DC generator is its simple formation and composition and also the fact that the parallel system is simple, and system strength issues are scarcer, unlike the alternators.


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