Laws contributing in dc generator
We have to understand
the concept of laws contributing in dc generator before understand the
operation of dc generator.
Wherever the change in
magnetic flux near the coil, the emf is induced in that coil. This is called as
faradays law of electromagnetic induction.
Just take a piece of
bar magnet and the LED circuit with coil. If we move the bar magnet front and
back near the coil, the LED will be glowing.
Fleming right hand rule
In general, the Flemings
right hand rule in defines the operation of dc generator. The thumb represents
the direction of force in conductor.
The fore finger
represents the direction of magnetic field and the middle finger represents the
direction of current in the coil.
Operation or dc generator
In dc generator, we should rotate the shaft of armature through Non-conventional sources. The Armature shaft having conductors converts mechanical energy in to electrical energy.
The
armature conductors are going to rotate and magnetic field and at stationary so
is known as dynamically induced emf.
The emf induced in the
conductor is minimum when the conductor is parallel to the magnetic field.
e=0
The conductor in inclination to the
magnetic field.
e=-nblvsinƟ
The negative sign
is derived from Lenz law. The induced emf produces current in the circuit
always opposes the rate of change of flux. Ɵ is an angel between flux and
conductor and v is the velocity of the conductor.
The maximum emf is
induced in the conductor when the conductor is perpendicular to the magnetic
field.
e=-nblv
Consider a simple dc generator with
permanent magnet. The coil is placed in between the permanent magnet. The
magnetic field lines are from north to south pole. The coil is having two
conductor AB and CD. The conductor AB is always connected with S2 and B2 likely
the conductor CD is always connected with load.
consider the generator
armature is always rotated in the clockwise direction.
Positive cycle
When the conductor is
parallel to the magnetic field there is no magnetic field cut by conductor so,
emf is zero in the conductors.
The conductors are
inclined to the magnetic field partially the magnetic field is cut by
conductors so, there is induced emf in that conductors according to Fleming
right hand rule. The current is flowing from the conductor ABCD to load through
B1 B2.
When the conductor is
perpendicular to the magnetic field the maximum emf is induced in the
conductors. The current is flowing from ABCD the conductor to load through B1 B2.
Negative cycle
Remember the
conductors are always connected to the slip rings S1 and S2. In this case the
emf is zero because of no magnetic fields are cut by conductors.
When the conductors
are in inclined angle partially the emf is induced in the conductors but, the
current is flowing from the conductors DCBA to load through B2 B1.
The emf is maximum
when conductor is perpendicular to magnetic field likely the current is flowing
from the conductor DCBA to load through B2 B1.
The number of cycles
per second called hertz.
Conclusion
There is no major
difference between the operation of dc generator and dc motor. The mechanical
energy is converted in to electrical energy vice versa.
Comments
Which
material is used in brush? Why?
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