The document covers fundamental concepts of electrical machines, focusing on electromagnetic induction laws, specifically Faraday's laws and Lenz's law. It details the construction and working principles of various DC machines, including generators and motors, highlighting types of windings and their characteristics, as well as the role of back emf. Additionally, it discusses transformers, their types, construction, working principles, and introduces induction motors, noting their advantages in industrial applications.

1. UNIT-4
ELECTRICAL MACHINES

2. Electromagnetic Induction
FARADAY’S LAW
•Michael Faraday formulated two laws
Faraday's First Law
Faraday's Second Law
•Lenz's law

3. Fleming’s Right
Hand Rule
Fleming’s Left Hand
Rule

4. Induced EMF

5. E
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6. DC GENERATOR
DC
GENERATOR
Output
Energy
(Electrical)
Input
Energy
(Mechanical)

7. DC GENERATOR
Working principle
• Faraday’s Electromagnetic Induction
• Dynamically Induced EMF

9. Construction of DC Machine

10. Construction of DC
Machine

11. Construction of DC
Machine

12. Armature (Rotor)

13. Field (Stator)
FIELD COILS

14. Commutator and Brush

15. Construction of DC
Machine

16. Types of Armature Winding
Armature Winding of a DC Machine is
wound by one of the two methods
• Lap Winding
• Wave Winding.
•The difference between these two is
merely due to the end connections and
commutator connections of the conductor.
•It may be simplex, duplex or multiplex.

17. No of parallel paths(A) is equal to the no of poles(P) A=P
High current, low voltage
LAP WINDING
Z=16, P=4, V(per conductor)=10V,
I(per conductor=10A)

18. WAVE WINDING
No of parallel paths(A) is equal to 2 (A=2)
Low current, High voltage
Z=16, P=4, V(per conductor)=10V,
I(per conductor=10A)

19. EMF Equation of DC
Generator

21. TYPES OF DC
GENERATORS
D
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22. SEPARATELY EXCITED DC GENERATORS

23. SERIES WOUND DC GENERATORS

24. SHUNT WOUND DC GENERATORS

25. COMPOUND WOUND DC GENERATORS
SHORT SHUNT LONG SHUNT

26. DC MOTOR
DC MOTOR
Output
Energy
(Mechanical)
Input
Energy
(Electrical)

27. DC MOTOR
Working principle
“whenever a current carrying
conductor is placed in an uniform
magnetic field it experiences a force”.

30. Working principle

31. Working principle

32. Back EMF(Eb)/Counter EMF

33. Back EMF(Eb)/Counter
EMF

34. Significance of back EMF
•Back EMF makes the d.c motor a self-
regulating machine
Let, Nr = running speed of the
motor
load load
N N
Eb
Eb
Ia
Ia

35. Torque Equation of DC
Motor
F= Force acting tangential on the surface
in Newton.
r= Radius of the armature in meters

36. Torque Equation of DC
Motor
The Torque exerted by this force on the
armature is given by
Ta= F r Nm
The work done in the armature by
this force F in one revolution is
W=(Force distance covered in 1
revolution)

37. Torque Equation of DC
Motor
The power developed by the armature = work
done in 1 sec

38. Torque Equation of DC
Motor
WKT electrical power converted into
mechanical power in the armature is EbIa
Watts.

39. TYPES OF DC MOTORS
D
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40. DC SHUNT MOTOR

41. DC SERIES MOTOR

42. L
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43. Power Flow

44. Power Flow

45. TRANSFORMERS
•Static Device
•Transfers energy from one circuit
other circuit.
•Step up Transformer
•Step down Transformer
•Efficiency is 95%-98%

46. Transformer
HV
Bushing
LV Bushing
Lightening
Arrester
conservator
Radiators

47. Construction

48. Windings

49. Core

50. Laminations of Core

52. Working Principle
•The working principle of the single phase
transformer is based on mutual induction
between two magnetically coupled windings

53. Working Principle

54. Types of Transformer
•CORE TYPE

55. Types of Transformer
•SHELL TYPE

60. Emf Equation of
Transformer

61. Emf Equation of
Transformer
The peak value of induced EMF is Em1
is given
by
RMS value of the induced EMF E1
is given by
Similarly RMS value of the induced EMF in secondary
is given by

62. 3Φ INDUCTION MOTOR
•They are the most widely used electric
motors in industry.
•constant speed from no-load to full-load.
•They are simple, rugged, low-priced, easy
to maintain and can be manufactured
with characteristics to suit most
industrial requirements.

63. DIFFERENCE
DC MOTOR
•Power is conducted
directly to the armature
through brushes and
commutator. Hence they
are Conduction Motor.
INDUCTION MOTOR
•Rotor will not get the
electric power by
conduction, instead by
induction. Hence they are
called as Induction
Motor.