State the function of a direct current (DC) generator.
A DC generator changes mechanical energy into electrical energy.
Where are generators used?
DC generators are used principally in electrical systems for mobile equipment
They are also used in power plants supplying DC power for factories
In certain rail way systems.
When is DC current most used
DC power is used extensively in communication systems and for battery
charging and electroplating operations.
note :
In a DC generator, the output voltage is a DC voltage, even though alternating current
(AC) is generated in the generator coils.
Important parts of a generator
The rotor - a cylindrical, laminated iron core that is
mechanically coupled to the drive shaft of the generator
The armature - The armature is the component of the generator that has the voltage (EMF) induced
into it.
Motor effect
When the magnetic field that causes an influence on the rotor goes in the opposite direction in which the rotor is driven
Differences between A separately excited generator develop voltage for either direction of rotation and self-excited units
A separately excited generator develops voltage for either direction of rotation where as self excited develop voltages in one direction only
REGULATION
Different types of generators have different voltage regulation characteristics
1) armature reaction
2) Rising
3) where the voltage remains constant with load
4) a generator with very poor regulation in that the output volt
age
Fun FACT
AC voltage is actually induced into the dc generator armature, and then mechanically
rectified by the commutator and brush assembly
Types of DC generators
Compound Wound Dc generator
Self-excited shunt DC generator
Separately excited Dc generator
what is a compound wound generator
A compound wound DC generator is a generator that combines series and shunt field windings.
important details of the compound-wound generator
(1)
the relative direction of the currents through both windings of a particular field pole
(2) the magnetic effects that these currents can produce.
cUmalative and differential
When the series winding is connected to aid the shunt winding, the generator
is called a cumulative compound-wound generator
if the series winding is connected
to oppose the magnetic shunt field, it is called a differential compound-wound
generator.
Why is it called separated excited generator
The current required by the field circuit may be supplied from a separate DC supply.
If this is the case, the generator is said to have a separately excited field.
Why is it called self excited
Self excited the current for the field is supplied by the
generator itself.
