What is a self excited DC generator?
A self-excited DC generator is the one whose field winding is excited by the current from the output of the generator itself. Depending upon the connection of field winding with the armature, the self-excited DC generators are of three types − Series Generator. Shunt Generator.
Which DC generators are self excited generators?
Modern DC generators with field coils are self-excited generators which get started with the initial current in the field coils. When generator is switched off, a small magnetism is developed in rotor iron which induced electromotive force in the armature due to which current is produced in the field windings.
How would you define separately excited DC generator and self excited DC generator?
In a separately excited (S.E.) machine, the field winding is connected to a separate voltage source while, in a self excited generator field winding is connected across the armature terminals (provides its exciting current) . Hence, the field winding has a large number of turns with a thin conductor.
What are self excited compound DC generators used for?
They are used to charge battery because they can be made to give constant output voltage. They are used for giving the excitation to the alternators. They are also used for small power supply (such as a portable generator).
What is DC compound generator?
Compound wound generators have both series field winding and shunt field winding. One winding is placed in series with the armature, and the other is placed in parallel with the armature. This type of DC generators may be of two types- short shunt compound-wound generator and long shunt compound-wound generator.
How does a self-excited DC generator work?
In self-excited DC generators, the field winding is connected across the armature. Since the field winding is connected across the armature, because of this induced emf a small current starts flowing in the field winding. If the field mmf due to this current aids the residual flux, total airgap flux increases.
How are self-excited DC generators classified?
Self-excited DC generators are classified based on the field coils and their position as follows: Shunt Wound Generators. Compound Wound Generators. Series Wound Generators.
How the polarity of a self-excited DC generator can be reversed?
When the armature is driven in either direction, an electrical polarity is established at the generator output terminals and at the brushes. As a result, the brush polarity in a separately-excited generator can be changed by reversing the rotation of the armature or the direction of the field current.
What are the advantages and disadvantages of a separately excited DC generator over a self-excited generator?
Separately excited DC generators have many advantages over self-excited DC generators. It can operate in stable condition with any field excitation and gives wide range of output voltage. The main disadvantage of these kinds of generators is that it is very expensive of providing a separate excitation source.
Where would you use a DC generator?
Applications of DC Generators They are used in DC motors where speed control is necessary. They are used as portable generators where low power supply is required. They are used in motorcycles as dynamos, in toys such as remote control cars and in appliances such as electric shavers.
What are the advantages and disadvantages of separately excited generator over a self-excited generator?
What are the types of self-excited DC machine?
The three types of self-excited DC generators are:
- Series Wound Generators.
- Shunt Wound Generators.
- Compound Wound Generators.
How is a self excited DC generator excited?
A self-excited DC generator is the one whose field winding is excited by the current from the output of the generator itself. Depending upon the connection of field winding with the armature, the self-excited DC generators are of three types −
What are the types of DC compound generators?
The DC compound generators are of two types − In a short shunt generator, only shunt field winding is connected in parallel with the armature. In a long shunt generator, the shunt field winding is connected in parallel with both series field and armature winding.
What is self excitation in case of a DC machine?
What is self excitation in case of a dc machine? Ans. The process of generating a magnetic field by means of an electric current is called excitation. Modern generators with field coils are self-excited, where some of the power output from the rotor is used to power the field coils.
How are field windings connected in a DC compound generator?
In case of a compound generator, there are two field winding on each pole – one is in series and the other is in parallel with the armature. The DC compound generators are of two types − In a short shunt generator, only shunt field winding is connected in parallel with the armature.