mapua ee153 q1 sir chua
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8/14/2019 MAPUA EE153 Q1 SIR CHUA
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DYNAMO
1. FUNCTIONAL VIEW
GENERATOR – a rotating machine converting mechanical energy
into electrical energy.
MOTOR – a rotating machine for converting electrical energy
into mechanical energy.
2. STRUCTURAL POINT OF VIEW
Dynamo- is a rotating machine which functions by producing a
relative motion between electrical conductors and a magnetic field.
ESSENTIAL PARTS OF A DC MACHINE
1. Magnetic frame or field yoke
Serves as a return path for all the circulating magnetic flux that
passes from the field poles to the armature.
Made of cast iron, cast steel, or rolled steel. Acts as mechanical support for the poles and also for the end
pieces which carry the bearings.
2. Pole cores and pole shoes
The pole core holds the pole windings coils (field coils). It serves
as magnetic path for the magnetic field pole produced by the
field coils.
Pole shoes spread out the flux in the air gap reducing the
reluctance of the magnetic path. It also supports the field coils.
Made of thin lamination of highly magnetic steel alloy.3. Pole coils or field coils
When current is passed through the field coils, they electro
magnetize the poles which produce the necessary flux that is
cut by revolving armature conductors.
4. Armature core
Serves as a support for the winding conductors that pass
through the magnetic field.
Provides as path for the magnetic flux through the armature
from North Pole to South Pole.
5. Armature windings or conductor
The winding wherein the voltage is induced electromagnetically.
Placed in the armature slots, which are lined with tough
insulating material. This slot insulation is folded over above the
armature conductors and is secure in place by special hand
wooden or fiber wedge.
6. Commutator Provide electrical connection between the rotating armature
coils and the stationary eternal circuit.
As the armature rotates, it performs a switching action,
reversing the electrical connections between the outside lines
and each armature coil voltages add together and result in a dc
output viltage.
7. Brushes
Collect the current from the commutator.
Normally made of carbon or carbon graphite or a copper filledcarbon mixture.
MAGNETIC CIRCUIT OF A DC MACHINE
1. Field Poles
2. Field Yoke
3. Air Gap
The space between the armature and the pole shoes (from top
of teeth to pole face).
4. Armature Core
ELECTRICAL CIRCUIT OF A DC MACHINE
1. Field Pole windings
2. Armature windings
3. Commutator
4. Brushes
SLOT PITCH/SLOT SPAN (Sp)
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Distance from center of one slot to center of adjacent slot
measured on the armature.
POLE PITCH
6 slots
The periphery of the armature divided by the number of poles
of the generator between two adjacent poles.
CONDUCTOR
The length of the wire lying in the magnetic field and in which
the emf is induced.
COIL OR WINDING ELEMENT
Two conductors along with their end connections constitute
one coil or winding element.a. SINGLE-TURN COIL
A single turn coil will have two conductors.
b. MULTI-TURN COIL
A multi-turn coil may have many conductors per coil side. The
group of wires or conductors constituting a coil side of a multi-
turn coil is wrapped with a tape as a unit and is placed in the
armature slot.
COIL SPAN OR COIL PITCH (Ys)
4 slots
It is the distance, measured in terms of armature slots (or
armature conductors) between two sides of a coil.
It is the periphery of the armature spanned by the two sides of
a coil.
a. FULL-PITCHED
The coil span or the coil-pitch is equal to the pole pitch. In this
case, the coil sides lie under opposite poles, hence the induced
emf will be maximum.
b. FRACTIONAL-PITCHED
If the coil-span is less than the pole-pitch, then the winding is
fractional-pitched. The total emf round the coil, which is the
vector sum of the two coil sides, is less compared to the full-
pitched.
PITCH OF A WINDING (Y)
It is the distance round the armature between two successive
conductors, which are directly connected together.
It is the distance between the beginnings of two consecutive
turns.
BACK PITCH (Yb)
It is the distance, measured in terms of the armature
conductors, which a coil advances on the back of the armature.
FRONT PITCH (Yf)
It is the number of armature conductors or elements spanned
by a coil on the front (or commutator end of n armature).
It is the distance (in terms of armature conductors between the
second conductor of one coil and the first conductor of the next
coil which are connected together at the front.
COMMUTATOR PITCH (Yc)
It is the distance (measured in commutator bars or segments)
between the segments to which the two ends of a coil are
connected.
SINGLE-LAYER WINDING
It is that winding in which one conductor is placed in each
armature slot.
POLE ARC
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Radial length of pole face
ONE LEADS OR FRONT END CONNECTION
Ends or leads that connect to the commutator bars.
TWO-LAYER WINDING
In this type of winding, there are two conductors or coil sides
per slot arranged in two layers. Usually, one side of every coil
lies on the upper half of one slot and the other side lies in the
lower half of some other slot at a distance of approximately one
pitch away.
LAP AND WAVE WINDINGS
These are the type of winding employed for drum type
armature. The difference between the two is merely due to thearrangement of the end connections at the front or
commutator end of the armature. The lap winding is also known
as multiple winding while for wave winding is also known as the
series winding.
RULES APPLIED TO BOTH TYPES OF WINDINGS:
1. The front pitch and the back pitch are each approximately equal to
the pole pitch i.e. windings should be full pitched. This results in
increased emf round coils.2. Both pitches should be odd otherwise it would be difficult to place
the coils properly on the armature. For example, if Yb and Yf were
both even, then all the coils sides and conductors would lie either in
the upper half of the slots or in the lower half. Hence, it would
become impossible for one side of the coil to lie in the upper half of
one slot and the other side on the lower half of some other slot.
3. The number of commutator segments is equal to the number of
slots or coils (or half the number of conductors) because the front
ends of conductors are joined to the segments in pairs.
4. The winding must close upon itself i.e. if we start from a given point
and more from one coil to another, then all conductors should be
traversed and we should reach a break or discontinuity in between.
TYPES OF GENERATOR:
1. SEPARATELY-EXCITED GENERATOR
Are those whose field magnets are energized from an
independent external source of dc current or it’s a winding also
called shunt field winding is connected to an outside source (a
battery or another dc generator). It is used for laboratory
experiment purpose where voltage, are likely to be varied.
2. SELF-EXCITED GENERATOR
Are those whose field magnets are energized by the current
produced by the generators themselves.
a. SHUNT-WOUND
The field windings are connected across or parallel with the
armature conductors and have the full voltage of the generator
applied across them. It is used for constant voltage application
like in electric welding.
b. SERIES-WOUND
In this case, the field windings are joined in series with the
armature conductors. As they carry full load current, they
consist of relatively few turns of thick wires. It is used for
constant current application like in series lighting.
c. COMPOUND-WOUND
It is the combination of a few series and a few shunt windings
and can either be short-shunt or long-shunt.
TYPES OF COMPOUND GENERATOR ACCORDING TO DIRECTION OF FLUX
1. CUMULATIVELY COMPOUNDED
The series field aiding the shunt field for supplying power and
lighting loads.
a. UNDER COMPOUNDED
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o The full load terminal voltage is less than the no load
voltage. It is used when the load is near from the
generator.
b. FLAT COMPOUNDED
o The full load terminal is the same as the no load
voltage. It is used when the load is at medium distance
from the generator.c. OVER COMPOUNDED
o The full load terminal voltage is greater than the no load
voltage. It is used when the load is far from the
generator.
2. DIFFERENTIALLY COMPOUNDED
The direction of flux of the series field winding opposes the
direction of the flux of the shunt field winding. It is used for
electric welding.
PRIME MOVERS:
1. Hydraulic Turbines
2. Steam Turbine
3. Internal Combustion Engine
COMPENSATING WINDING
Connected in series with the armature.
Used to neutralize armature reaction.
INTERPOLE WINDING
Connected in series with the armature. Used for spark less
commutation.
DIVERTER RESISTANCE
Connected in parallel with the series field.
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