The document outlines the course content for EECE-259, which covers electrical and electronics technology. The course covers principles and characteristics of DC generators, DC motors, AC generators/alternators, induction motors, synchronous motors, and transformers. It also discusses losses in generators and motor characteristics. Key references on electrical machinery fundamentals and AC/DC machines are provided.
2. Course Outline Sec A
DC Generator
Principles
Types
Performances and characteristics
DC Motor
Principles
Types
Performances and characteristics
Speed control and starters of motors
3. Course Outline Sec A
AC Generator/Alternator
Principles
Performances and characteristics
Induction Motor
Principles
Performances and characteristics
Synchronous Motor
Principles
Performances and characteristics
AC Motor
4. Course Outline Sec A
Transformer
Principles
Single phase transformer
Equivalent circuit and laboratory testing
Losses
Introduction to three phase transformers
5. Book References
A Text Book of Electrical Technology (AC, DC
Machines) – B.L Theraja & A.K. Theraja; S.
Chand & Company Ltd.
Electrical Machinery Fundamental - Stephan
J. Chapman; McGraw-Hill.
Direct and Alternating Current Machhinery-
Rosenblatt; Friedman
6. What is Electricity?
Electricity is energy transported by
the motion of electrons
**We do not make electricity, we
CONVERT other energy sources into
electrical energy**
7. Energy Conversion Options for Electricity
Non-Thermal Paths
• Source to Electrical
Source Converter
Sun Photovoltaic (photon to electron)
Chemical Fuel Cell
• Source to Potential/Kinetic to Mechanical to Electrical
Source Converter Kinetic to Mechanical Mech to Electrical
Dam Penstocks Turbine (water) Generator
Tides Machine Turbine (air or water) Generator
Wind N/A Turbine (air) Generator
8. Energy Conversion Options for Electricity
Thermal Paths
• Heat to Mechanical to Electrical
Source Heat to Mechanical Mech to Electrical
Geothermal Turbine (vapor) Generator
OTEC Turbine (vapor) Generator
• Stored Energy to Heat to Mechanical to Electrical
Source Reactor Heat to Mechanical Mech to Electrical
Fuel Combustor Turbine (gas or vapor) Generator
U, Pu Reactor Turbine (gas or vapor) Generator
Sun Collector* Turbine (gas or vapor) Generator
H, H2, H3Reactor Turbine (gas or vapor) Generator
* More a modifier or concentrator than a reactor
10. Where do we get our
Electricity?
• Fossil – Coal, Natural
Gas, Oil – 550 Gigawatts
(GW)
• Nuclear – 200 GW
• Hydro – 75 GW
• Geothermal – 2.3 GW
• Other Renewable –
Wind, Solar, OTEC – 13.6
GW
11. Electrical Machine
• What is Electrical Machine?
An electrical machine is the apparatus that
converts energy in three categories: Generators
which convert mechanical energy to electrical
energy, Motors which convert electrical energy
to mechanical energy, and Transformers which
changes the voltage level of an alternating
power.
12. Faraday Effect
• Faraday Effect
• Basic Concepts
• Voltage – V – Potential to Move Charge (volts)
• Current – I – Charge Movement (amperes or amps)
• Resistance – R – V = IxR (R in =ohms)
• Power – P = IxV = I2xR (watts)
13.
14. Faradays Law
• The EMF generated is proportional to the rate
of change of the magnetic flux.
aabbbbbbbbbbbbbbb
15. Lenz’s Law
Lenz’s law: If an induced current flows, its direction is
always such that it will oppose the change which
produced it.
Flux decreasing by right move
induces loop flux to the left.
N S
Left motion
I
Induced B
Flux increasing to left induces
loop flux to the right.
N S
Right motionI
Induced B
19. DC Generator Principle
An electrical generator is a machine which converts mechanical energy (or power)
into electrical energy (or power).
20. DC Generator Principle
The energy conversion is based on the principle of the production of dynamically
(or motionally) induced e.m.f. whenever a conductor cuts magnetic flux, dynamically
induced e.m.f. is produced in it according to Faraday’s Laws of Electromagnetic
Induction. This e.m.f. causes a current to flow if the conductor
circuit is closed.
28. N
S
Motion is 45° to flux.
Induced voltage is 0.707 of maximum.
SINGLE LOOP GENERATOR
29. Motion is parallel to flux.
N
S
No voltage is induced.
Ready to produce another cycle.
SINGLE LOOP GENERATOR
30. COMMUTATION
For making the flow of current unidirectional in the external circuit, the slip-
rings are replaced by split-rings .The split-rings or commutator are made out of
a conducting cylinder which is cut into two halves or segments insulated from
each other by a thin sheet of mica or some other insulating material. the coil
ends are joined to these segments on which rest the carbon or copper brushes.
31. COMMUTATION
It is seen (a) that in the first half revolution current flows along (ABMLCD) i.e. the
brush No. 1 in contact with segment ‘a’ acts as the positive end of the supply and ‘b’ as
the negative end. In the next half revolution (b), the direction of the induced current in
the coil has reversed. But at the same time, the positions of segments ‘a’ and ‘b’ have
also reversed with the Fig. result that brush No. 1 comes in touch with the segment
which is positive i.e. segment ‘b’ in this case. Hence, current in the load resistance
again flows from M to L. The waveform of the current through the external circuit is as
shown in Fig. This current is unidirectional but not continuous like pure direct current.
32. Practical Generator
1. Magnetic Frame or
Yoke
2. Pole-Cores and Pole-
Shoes
3. Pole Coils or Field
Coils
4. Armature Core
5. Armature Windings
or Conductors
6. Commutator
7. Brushes and Bearings
37. Armature Windings
Lap and Wave Windings
Two types of windings mostly employed for drum-type armatures are known as
Lap Winding and Wave Winding. The difference between the two is merely due to
the different arrangement of the end connections at the front or commutator end of
armature. Each winding can be arranged progressively or retrogressively and
connected in simplex, duplex and triplex.
38. Armature Windings
Uses of Lap and Wave Windings
The advantage of the wave winding is that, for a given number of poles and
armature conductors, it gives more e.m.f. than the lap winding.
Conversely, for the same e.m.f., lap winding would require large number of
conductors which will result in higher winding cost and less efficient utilization of
space in the armature slots.
Hence, wave winding is suitable for small generators especially those meant for 500-
600 V circuits.
Another advantage is that in wave winding, equalizing connections are not
necessary whereas in a lap winding they definitely are.
However, when large currents are required, it is necessary to use lap winding,
because it gives more parallel paths.
Hence, lap winding is suitable for comparatively low-voltage but high-current
generators whereas wave-winding is used for high-voltage, low-current machines.
42. Iron / Core Loss in Armature
(i) Hysteresis Loss (Wh)
If the magnetic field applied to a
magnetic material is increased
and then decreased back to its
original value, the magnetic field
inside the material does not return
to its original value. The internal
field 'lags' behind the external
field. This behaviour results in a
loss of energy, called the
hysteresis loss, when a sample is
repeatedly magnetized and
demagnetized.
43. Iron / Core Loss in Armature
(ii) Eddy Current Loss (We)
When the armature core rotates, it
also cuts the magnetic flux. Hence,
an e.m.f. is induced in the body of
the core according to the laws of
electromagnetic induction. This
e.m.f. though small, sets up large
current in the body of the core
due to its small resistance. This
current is known as eddy current.
The power loss due to the flow of
this current is known as eddy
current loss. This loss would be
considerable if solid iron core
were used.
44. Losses in a Generator
Usually, magnetic and mechanical losses are collectively known as Stray
Losses. These are also known as rotational losses for obvious reasons.
47. DC Generator Characteristics
In general, three characteristics specify the steady-state
performance of a DC generators:
1. Open-circuit characteristics: generated voltage versus field
current at constant speed.
2. External characteristic: terminal voltage versus load current
at constant speed.
3. Load characteristic: terminal voltage versus field current at
constant armature current and speed.
48. DC Generator Characteristics
Open-Circuit and Load Characteristics
The terminal voltage of a dc
generator is given by
aa
mf
aaat
RI
dropreactionArmatureIf
RIEV
,
49. DC Generator Characteristics
It can be seen from the external
characteristics that the terminal
voltage falls slightly as the load
current increases. Voltage regulation
is defined as the percentage change
in terminal voltage when full load is
removed, so that from the external
characteristics,
External characteristics
100
V
VE
regulationVoltage
t
ta
