What is a generator?
The generator is basically a very common machine that we all
know more or less. Generators basically generate power.
Turning on the generator will generate a certain amount of
electrical energy. Generators basically convert mechanical power into
electrical power. The generator is a type of machine.
Types of DC generators
There are 2 types of generators based on excitement
- Separately excited generator: This type of generator is mainly powered by a magnetic field or energized by an external source DC current.
- Self Excited Generator: The magnetic field is energized by the current generated by the generator. It does not require any external source.
Self Excited Generator
There are three types of Self Excited generators.
- Shunt generator
- Series generator
- Compound generator
Compound generator
There are two types of compound generators
- Short shunt compound generator
- Long shunt compound generator
What is induction or induced current?
The word Induction comes from Induce. This means depositing
something. This means that power is being stored here.
If a conductor or a conductive position is changed or moved
within a certain place or region around an electromagnet, electricity will be
generated at both ends of that conductor.
This is called electromagnetic induction or electromagnetic
induction. The electricity we get at the output is called induced current.
Some of the major differences between electrical and electronics.
Discussion on the structure of DC generator
Yoke or frame:
The outer covering of a machine is called a yoke or frame.
For small generators, this yoke uses cast iron and for large generators steel is
used.
Starter magnet/field magnet
It includes pole show and pole core. The pole show spreads
the magnetic field all around in its interior space.
Field winding and pole coil
It is made of copper wire which is beautifully arranged in
each pole.
Armature core
The part inside the generator that is able to rotate is
called an armature. It looks like a cylinder with a copper conductor twisted.
Armature Winding:
This part is the rest of the armature slot that is twisted.
Armature:
It is a rotating part of a generator with a protruding shaft
attached.
Commuter:
It looks like a round bearing through which current comes
and accumulates here to go to the next step.
Brush:
It looks a lot like a rectangle. The brush is used for
contacts that supply the output. It is made of carbon graphite.
Slip ring
It is connected to the commuter.
Brush drop:
This causes a slight voltage drop due to the internal
resistance of the generator. It is usually not more than 1-2 volts.
The names of different parts may be different or additional
parts may be added depending on the generator design.
Fleming's right-handed rule
DC Generator voltage is generated by electromagnetic
induction. According to Lenges's formula, the direction of voltage is such that
it causes a change in the current flux caused by it. According to Lenz's
formula, it is very difficult to determine the direction of the voltage
generated by the generator. So we can use the right-hand rule to determine the
direction of the voltage.
If the thumb, forefinger, and middle finger of the right hand
extend at right angles to each other, then if the index finger points in the
direction of the magnetic force line and the thumb points in the direction of
rotation of the conductive wire, then the middle finger will point in the
direction of output voltage.
How the DC generator works
We know that when a conductive magnet intersects a flux, E,
M, F is generated in that conductor according to Faraday's electromagnetic
induction formula. We will discuss a single loop with a single rotation that
rotates at a certain speed in a uniform clockwise direction. When it continues
to rotate, it will constantly cut the flux at both ends, creating E, M, F at
both ends.
Adding E, M, F to these two ends will create a total E, M, F
in the circuit and create voltage difference or voltage at both ends of the
load. And the magnetic flux always goes from the north pole of the magnet to
the south pole. Now below is how the generator will work in different
positions.
Position A: No E, M, F is formed when the loop is
located at A i.e. E, M, F = 0. This is because the loop at position A does not
cut any flux. The two ends of the loop are parallel to the flux.
Position B: When the loop is at B, the two ends of the
loop rotate 90 degrees. When the North Pole and the South Pole come together,
the maximum flux is cut off and the maximum A, M, F is formed.
Position C: In this position the two ends of the flux
move forward 90 degrees opposite half of the flux i.e. a total of 180 degrees
forward and E, M, F is again 0. It will now be towards the N pole and the edge
which was the N pole will now be towards the S pole. As a result, opposite E, M, F will
be created i.e. maximum E, M, F will be created on the negative side.
Position A: At this position, the loop will return to
its original position. This process will happen again and will continue.
Difference between AC Generator and DC Generator
We know that the armature winding of any generator first
generates a variable voltage or AC. In the case of DC generators, this AC is
converted to DC by a commuter and it is supplied with the load. The main difference
between a DC and an AC generator is a commuter.
What does the emf generated by the DC generator depend on?
The E, M, Fs produced by DC generators depend on a number of
factors
- On the magnetic field
- On the conductor
- On the relative speed within them
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