TYPES OF D.C GENERATOR

The power station of modern design generate practically only three phase alternating current.A large part of this power is used in the form of alternating current in industry,for lighting and domestic needs.When industrial needs make it necessary too or when it is of greater advantage to use direct current .It is generally obtained by converting A.C to D.C with help of converters of ionic or machines type.

As primary sources of power,D.C generators are mainly used in self contained plants such as automobiles and airplanes,for electric arc welding,train car lighting,in submarines etc,.

Types of D.C generator :

sending current through the field winding for production of magnetic flux is called Excitation.Depending on the method of excitation D.C generator are classified as

1.separately excited D.C generators

2.self excited D.C generators.

1.Separately excited D.C generators

These generators whose field magnets are energised from independent external source of D.C current.

 In separately excited D.C generators,the exciting field current is supplied by a separate source as shown in above.

2.Self excited D.C generators :

These generators whose field magnets are energised by the current produced by the generators themselves.Due to residual magnetism there is always present some flux in the poles .When the armature is rotated,some emf and hence some induced current produced which is partly or fully passed through the field coils there by strengthening the pole flux.

self excited generators can be divided in to accordance with how field winding is connected into generators as follows,

(i) D.C shunt generators

(ii) D.C series generators

(iii)D.C compound generators

(i)D.C shunt generators:

In shunt generators the field winding is connected in parallel with the armature winding terminals and have the full voltage of the generator across them.

some important relations are

The shunt generator field winding has many turns of fine wire having high resistance.In DC shunt generator the armature current (Ia) will be the sum of load current (I) and the field current(Ish).