“Energy can be converted from one form to other form” – A generator does the same – it converts mechanical energy to electrical energy. Mechanical energy can be created by using water turbines, steam turbines, internal combustion engines etc. And a generator converts this mechanical energy to electrical energy. Generators can be broadly classified as AC generators and DC generators. Here lets take a look the the types of DC generators.
DC generators are classified based on their method of excitation. So on this basis there are two types of DC generators:-
1. Separately excited DC generator
2. Self excited DC generator
Self excited DC generator can again be classified as
1) DC Series generator 2) DC Shunt generator and 3) DC Compound generator.
1) DC Series generator 2) DC Shunt generator and 3) DC Compound generator.
Let’s take a brief look at how all these differ.
1. Separately excited DC generator
As you can guess from the name itself , this dc generator has a field magnet winding which is excited using a separate voltage source (like battery). You can see the representation in the below image. The output voltage depends on the speed of rotation of armature and field current. The higher the speed of rotation and current – the higher the output e.m.f
2. Self Excited DC Generator
These are generators in which the field winding is excited by the output of the generator itself. As described before – there are three types of self excited dc generators – they are 1) Series 2) Shunt and 3) Compound.
A series DC generator is shown below in fig (a) – in which the armature winding is connected in series with the field winding so that the field current flows through the load as well as the field winding.Field winding is a low resistance,thick wire of few turns. Series generators are also rarely used!
A shunt DC generator is shown in figure (b), in which the field winding is wired parallel to armature winding so that the voltage across both are same. The field winding has high resistance and more number of turns so that only a part of armature current passes through field winding and the rest passes through load.
Long shunt:- Here the shunt field winding is parallel to both armature and series field winding (Rse is wired in series to the armature).
So you have got a basic idea about the types of DC generators! Now you may know that these generators are used only for special industrial purposes where there is huge demand for DC production. Otherwise electrical energy is produced by AC generators and is transmitted from one place to other as AC itself. When a DC power is required, we usually convert AC to DC using rectifiers.
You can refer this good blog on Electrical Circuits – to learn more about basic electrical engineering concepts.
