Principle of Operation of DC Generator in Easy Ways

 

    The first electromagnetic generator was invented in 1831 by British scientist Michael Faraday. The reverse operation of  electric DC generator is DC motor.

Laws contributing in dc generator

    We have to understand the concept of laws contributing in dc generator before understand the operation of dc generator.

    Wherever the change in magnetic flux near the coil, the emf is induced in that coil. This is called as faradays law of electromagnetic induction.

    Just take a piece of bar magnet and the LED circuit with coil. If we move the bar magnet front and back near the coil, the LED will be glowing.

 

Fleming right hand rule

    In general, the Flemings right hand rule in defines the operation of dc generator. The thumb represents the direction of force in conductor.

    The fore finger represents the direction of magnetic field and the middle finger represents the direction of current in the coil.

 

Operation or dc generator

    In dc generator, we should rotate the shaft of armature through Non-conventional sources. The Armature shaft having conductors converts mechanical energy in to electrical energy. 

The armature conductors are going to rotate and magnetic field and at stationary so is known as dynamically induced emf.

    The emf induced in the conductor is minimum when the conductor is parallel to the magnetic field.

    

 e=0

    

The conductor in inclination to the magnetic field.

 

e=-nblvsinƟ

 

    The negative sign is derived from Lenz law. The induced emf produces current in the circuit always opposes the rate of change of flux. Ɵ is an angel between flux and conductor and v is the velocity of the conductor.

    The maximum emf is induced in the conductor when the conductor is perpendicular to the magnetic field.

e=-nblv

 

Consider a simple dc generator with permanent magnet. The coil is placed in between the permanent magnet. The magnetic field lines are from north to south pole. The coil is having two conductor AB and CD. The conductor AB is always connected with S2 and B2 likely the conductor CD is always connected with load.

    consider the generator armature is always rotated in the clockwise direction.

 

Positive cycle

    When the conductor is parallel to the magnetic field there is no magnetic field cut by conductor so, emf is zero in the conductors.

    The conductors are inclined to the magnetic field partially the magnetic field is cut by conductors so, there is induced emf in that conductors according to Fleming right hand rule. The current is flowing from the conductor ABCD to load through B1 B2.

    When the conductor is perpendicular to the magnetic field the maximum emf is induced in the conductors. The current is flowing from ABCD the conductor to load through B1 B2.

 

Negative cycle

    Remember the conductors are always connected to the slip rings S1 and S2. In this case the emf is zero because of no magnetic fields are cut by conductors.

    When the conductors are in inclined angle partially the emf is induced in the conductors but, the current is flowing from the conductors DCBA to load through B2 B1. 

    The emf is maximum when conductor is perpendicular to magnetic field likely the current is flowing from the conductor DCBA to load through B2 B1.

    The number of cycles per second called hertz.

 

Conclusion 

    There is no major difference between the operation of dc generator and dc motor. The mechanical energy is converted in to electrical energy vice versa. 

 

Comments

     Which material is used in brush? Why?

    

 

 

 

    

 

    

 

Basic Construction of DC Generator and it parts

    

    Do you know? There is no major difference between construction of DC generator and DC motor. In general, DC generator is a machine which converts Mechanical energy into Electrical energy. In motor the operation is vise versa.

Lets talk about the Constructional Features of DC generator. The main parts of generator are discussed one by one.

image credit: Gillett&#039, distributed under a CC BY 2.0 licenses.

Yoke

image credit: Toshinori baba, distributed under a CC BY-SA 3.0 licenses.

    The outer body or frame of the dc generator is known as yoke. The inner side of the yoke is fixed with field poles for creating the magnetic flux in the air gap.

    In general, the yoke serves the two main function

    It should give mechanical support for the field poles and protect the dc generator from surroundings. On the other hand, it provides the magnetic flux produced by the electromagnetic poles. The material used for making yoke is cast iron or cast steel

 

Pole shoe and pole core

    The arrangement of magnetic field winding is provided by inner part of yoke is known as pole shoe. By the help of former the field winding is wound in exact number of turns and then fixed with pole shoe. They spread the flux in the air gap and reduce the reluctance. 

    The pole core and pole shoe are made with lamination of steel to reduce the losses. The thickness is varied from 1 to 0.25 mm. 

 

Field coil

    To create the magnetic field between the poles the electromagnetic field coils are implemented. These coils are usually made up of copper to carry the current.

     First of all, the winding is made over the former for correct dimension and number of turns and the former wound is put over the pole cores.

 

Armature core

    The main part of dc generator is armature. the armature consists of number of conductors placed in the slots to produce the electricity when the magnetic fields are cut by armature conductors.

     It is drum shaped with laminated core. The Armature is perforated with air duct which allows the flow of air through the armature for reducing temperature.

     We can see the keyway in the armature for fix the shaft. We can reduce the losses in armature by increasing multiple number of laminations. Because of increasing resistance by decreasing the thickness of laminations.

 

Armature winding

    These are current carrying conductors when the conductors cut magnetic field produces the direction of current by Fleming right hand rule. It could also former wound and then wound on armature by automated coil puller machine. 

    The windings are made with two methods lap and wave windings. In lap winding number of paths is equal to number of conductors in wave winding the parallel path is always two.

     conductors are wound form the front end of commutator through armature. The conductors are placed in the armature slots which are wound with insulating material.

 

 Commutator

image credit: Rs1421, distributed under a CC BY-SA 3.0 licenses.

    The one of the important parts in the dc generator in commutator. The function of commutator is to facilitate collection of current from all the conductors wound on the armature. So, we can realize the number of coils is equal to number of segments.

     it converts the alternating current induced in the armature conductors in to unidirectional current in the external current having load. It is cylindrical shaped and built up with wedge shape of high conductivity.

     The segments are insulated from each other by the layers of higher resistance like mica.

 

Brushes and bearings

    The Brushes are used to collect current from the commutator. They are made with carbon or graphite and it is rectangular structure.

    The roller bearings are frequently employed for higher reliability. The ball and rollers are packed in hard oil for reduced bearing wear.

 

Conclusion

    Construction of dc motor is basic prerequisite for further with operations and winding methodology.

 

Comments

    Why the armature core is laminated in all DC generator?