DC Generator Animation
DC machine is generally an alternating current machine in which the current vary sinusoidally and is furnished with a special device named commutator.
The commutation is the process by which the AC is converted into DC.
The commutation process also helps in keeping the armature field stationary in space.
The DC generator is the device which helps in converting the mechanical energy into electrical energy.
It is based on the principal that when the conductor is rotated in a magnetic field and amount of induced voltage is generated in the conductor. DC generators are used only for special applications and localised DC power generator.
Construction of DC Generator:
A DC generator mainly consists of four main parts: (a) field windings (b) armature (c) commutator (d) brushes
The magnetic field windings or system is stationary part of the DC generator.
The main prpose of the field system is to produce a uniform magnetic field in the air gap, within which the armature rotates.
Electromagnets are used and preferred in comparison to with permanent magnet due to its greater magnetic effect.
The armature is the rotating part of the DC generator, the generator of the DC generator cosists of a shaft ipon which a laminated cyclindrical core is mounted called armature core.
The armature core has slots in its outer surface. The laminations are insulated from each other and tightly clamped together.
The armature is the one of the very important requirement of DC generator without the whole operation would fail.
The connected arrangement of slots and conductor is better known as armature winding.
The commutator is one of very important part of DC machine which rotates with the armature; the main function of commutator is to convert DC to AC which also keeps the magnetic flux stationary.
As alternating voltage is produced in the coil, which is rotating in a magnetic field but direct is required in the external circuit and for this purpose we need a commutator.
The commutator receives the current from brushes which are placed in the rotating armature as well.
Carbon brushes are used in DC generators and are generally needed to collect from the armature winding.
Two or more brushes are used in commutator for uniform current distribution.
Each brush is supported in metal box called brush box.
The current so produced in the armature is then passed to the external circuit with the help of these brushes.
Excitation of DC Machine:
In DC generator the field coils is excited in order to produce the magnetic flux.
The production of the useful magnetic flux with the application of electric current to the field windings is better termed as excitation.