Construction and working of dc generator | principle, compound wound

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Construction and Working principle of DC generator:

DC generator construction and working are same as the construction of any DC machines. The two major types of DC machines are DC Generator and DC motor. The difference between the two is that DC generator converts mechanical energy to electrical energy while DC motors convert electrical energy to mechanical energy.

The construction of DC generator can be understood well by dividing it into major parts. I am going to discuss every major part of DC generator one by one along with its construction.

DC Generator Stator: The DC generator has a stationery part, the outside covering of DC generator is known as stator. What is the function of stator?

It provides physical and mechanical support. Along with the mechanical physical strength stator also provides path for the field flux to establish in the DC generator.

Yoke: This stationary part is also called by the name of Yoke. The stator and yoke are similar or we can even say they are same. Yoke is the stationary supporting covering part of the dc generator. It is made up of cast steel.

What are the components that are attached with the stator in dc machine?

Poles: Poles in DC generator construction are attached with the stator. Poles are responsible for the production of field flux. Field flux is necessary to make DC generator work. In simple language we can say that poles are a kind of electromagnet to produce flux. Field windings are present on the poles. When these field windings are energized, the pole produces field flux.
Construction and Working of DC Generator

Pole Shoe: The poles in dc generator construction are extended to make the pole shoe. Why pole shoes are used? To increase the area of flux generation into the machine pole shoes are used.

Field Windings: The field windings are wound over the poles and these are responsible for the production of flux in the DC generators.

Stationary part, Stator of DC generator = Poles + Field windings

The central rotating part of DC generator is known as armature. What is the function of armature?
The voltage gets induced in the armature. The central cylindrical drum like structure which rotates is known as the armature. There are two types of windings in dc machine, one is field winding and other is armature winding. The armature winding housed on armature when rotates it cuts the flux produced by the field windings and poles. When the main flux is cut by the rotating armature winding emf gets induced in it.

Armature Windings: Armature windings are of two types: 

Lap Winding and Wave Windings

Armature Core: It is made of steel laminated sheets. Laminations are used in armature core to reduce eddy current losses.

Other parts are also present in the central part of dc generator construction, these includes shaft, bearings, commutator, brushes etc.

Shaft is the central rod over which all the rotating parts are attached. The external mechanical energy is also transferred to the dc generator with the help of this shaft.

Commutator in dc generator: What is the function of commutator in dc generator construction and working?

Commutator in dc generator working principle is used for the conversion of ac into dc. Inside the generator ac gets induced, this ac is further converted to DC with the help of this commutator. Commutator is like rectifier which converts ac into dc.

Bearings: In dc generators for smooth rotations without frictions are needed, this is achieved by using bearings in the mechanical rotating assembly of dc generator.

What are Brushes in DC generator? Construction and working of DC generator use brushes for taking out induced emf to the outer electrical circuits. Because the central armature part is rotating, it is not possible to attach fixed connections to the armature windings. When armature starts to rotate these fixed connections get broken. Brushes in dc generator solve this problem, and it just touches to the commutator, not permanently fixed. As armature rotates the brushes slide over the commutator to collect the energy.

Due to the movement between armature and brushes, sparks often produces in the dc generator. It results in lower efficiency, more wear and tear. Brushes are made up of carbon and they need to be changed in regular maintenance work.
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