what is DC Generator? More About DC Generator with diagram

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The machine that converts mechanical energy into electrical energy is known as a generator. This generated electrical energy can be used for various purposes and depending on its utility. The generated electrical energy is further transmitted via the power grid and distribution lines.

There are two types of generators (based on output giving capability)…

• AC Generator
• DC Generator

Now after the small summary on generators now we will discuss our topic DC Generator. After going through this post you will be able to all the question that comes under this topic. here we will cover ………

1. What is a DC generator?
2. Construction and parts of DC Generator?
3. Working principle of DC Generator?
4. EMF equation for DC Generator
5. Losses
6. Types of DC generator
7. Applications of DC Generator

So now let’s start the discussion…

What is DC Generator?

DC generator is a device that produces direct current output from Mechanical input. It has several uses in the electrical engineering and electronics industry, particularly in the automotive industry. The electric power used in vehicles is a combination of alternating current (AC) and direct current (DC). DC power is applied directly to electronic components that are part of a vehicle’s electronic system

It is widely used in electrical engineering and electronics applications to provide electric power from the utility grid to portable electronic devices such as laptops, smartphones, or PDAs.

DC generator is used in many fields like Agriculture, Machine building, Metal and Plastic industry, Electronics industry, etc.

 

Constructional details

Stator-
The stator is the arrangement of two magnetic poles on a core material in such a way that two opposite faces of the pole are opposite to each other. The main function of the stator is to provide sufficient magnetic flux to the rotor coil so the voltage can be induced. Depending on the field winding supply in the stator DC Generator can be further classified.

Rotor- 
The rotor is the main part where the induction of magnetic field and generation happen. The rotor is made up of a conducting material and it consists of several conductor coils. core has a slot throughout its peripheral to hold the conductor coil. And the core is laminated to prevent the eddy current loss.

Armature Winding-
Armature windings are nothing but the coils which are placed in the rotor slot. The coils are closed and distributed over the area of the rotor. They are connected in series to parallel for enhancing the sum of produced current. The number of armature winding coils is responsible for the amplitude of current and voltage generated in the generator. Windings are two types …

1. Lap winding.
2. Wave winding.

Yoke-
The outer structure of the Dc generator which provides the path to flow flux and provides mechanical balancing to the overall system is called a yoke. It is made up of either cast iron or steel.

Pole Shoe-
Pole shoes are the arc-shaped structure that is attached to the stator. The Pole shoe spread the magnetic flux to the rotor. To spread more flux we make pole shoes in ark shape.

Commutator-
A commutator is a converter that converts the generated ac voltage into DC. Here inside the rotor due to the faradays law of induction, an AC voltage is getting produced and the commutator makes DC out of it. It is made up of two brushes and a slip ring. It is placed on the shaft and its segments are laminated from each other. The commutator should be a rotating type.

Brushes-
Brushes make the electrical connection between the rotating body (Rotor) and the load. Brushers are made of graphite. brushes are such that the rotor can move easily with the connection of brushes.

Working Principle of DC Generator-

Before starting this first of all we have to understand the two most basic laws of electrical induction.
1) Faraday’s Law of electromagnetic induction- when a current-carrying conductor is placed in a time-varying magnetic field then EMF will be induced in the conductor/coil.
2)Flemings Right Hand Rule- when a moving conductor is placed in a magnetic field then the direction of induced EMF can be found by this rule. If the forefinger of your right hand denotes the direction of flux and the thumb shows the motion of the conductor with respect to the field then the middle finger will denote the direction of induced voltage or current.

Now let’s understand the working of the DC Generator .to better understand the working we have to consider a situation where only one conductor coil is placed in a magnetic pole now it is moving in the clockwise direction and the flux direction is right to the left side. in that situation, according to Fleming’s right-hand rule, the direction of induced emf is as shown as below figure.

so now current is going from b to a for the first half of rotation.

But when the same conductor side comes near the north pole then the direction of the motion of the conductor will be upward and according to the Flemings right-hand rule now the current direction will be exactly opposite to the previous case.

We can observe that current direction and emf direction are not the same for two half-cycle within a complete cycle. It means here AC current is producing now the question is how can we connect this AC supply in a DC load so now commutator comes into the picture. The commutator changes the negative half cycle of the current into the positive cycle with the help of a slip ring and brushes. And after Commutation, it can be connected with a DC load.

EMF Equation for DC Generator

ø = flux per pole(weber)

Z = no of armature conductor

A = number of parallel path

N = speed of rotation in RPM

E_g = Generated emf in armature

P = number of poles.

flux cut by one conductor in a rotation =Pø

Speed in rotation per second = N/60

time is taken to complete a rotation = 60/N

E_g per conductor = dø/dt = Pø/(60/N)

EMF  per parallel path = Eg = PΦNZ / 60A

Losses in DC Generator-

There is no machine that can convert 100% of energy from one form to another. DC generators also have some extent of losses between Input energy and Output energy. In DC generator two types of major loss are there…

Core loss-

Core loss is the pure magnetic properties of magnetic material in a core loss that occurs due to hysteresis and eddy current loss. Here in the DC generator, we laminate the core to prevent core loss.

Copper loss –

Copper loss or winding loss is the loss that occurs due to resistance. In DC machine core loss are there for Armature winding resistance, Field winding resistance, and voltage drop near brush contact. As they are all resistance loss so when current flow through the machine is zero there is no copper loss.

Classification of DC Generator

Separately excited DC Generator

supply for field winding (to create magnetic field) given externally. In this type of machine, we can vary the output voltage by manipulating the field current with the help of a rheostat. Excitation is independent of the terminal voltage.

Self-excited DC Generator

A self-excited DC generator is one whose field winding is excited by the current from the output of the generator itself. Depending upon the connection of field winding with the armature, the self-excited DC generators are of three types − Series Generator. Shunt Generator.

Applications of DC Generator

separately Excited

1. Rarely used for commercial application because it needed an extra excitation system.
2. Used for special power supply in aircraft, ships, etc.
3. Used in ward Leonard speed control method.
4. Used as excitation system in Alternator.

Self-excited

1. shunt generator used in small rating DC power supply.
2. In parallel operation shunt generators are useful.
3. charging a battery.
4. used as an excitation system.
5. DC series Generator has high starting torque for that reason it has very useful application in industry.
6. DC series Generator used as a booster in DC traction.

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It is widely used in electrical engineering and electronics applications to provide electric power from the utility grid to portable electronic devices such as laptops, smartphones, or PDAs.

DC generator is used in many fields like Agriculture, Machine building, Metal and Plastic industry, Electronics industry, etc.

I hope you have found the answers to all your questions through this post. About DC Generator  After that, if you have any questions, you can comment in our comment box.

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