1. UNIT – II
ELECTRICAL MACHINES

2. Types of Electrical Machines There are basic three rotating machines,
1.DC Machines
i. Shunt
ii. Series
iii. Compound
2.Synchronous Machines (A.C)
i. Salient Pole type
ii. Non Salient Pole type
3.Induction Machines (A.C)
i. Squirrel Cage type
ii. Slip Ring type

3. Construction of DC Machines:
Yoke

4. Various parts of DC machines: 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
Change in flux linkages of a coil may occur in two ways:
The coil remains stationary withy respect to flux, but flux through it changes with time. This induced emf is known as statically induced emf. E.g. Transformers.
Flux remains constant and stationary but coil moves relative to it. This induced emf is known as dynamically (or motional) induced emf. E.g. Generators.

5. EMF Equation of DC Machines:

6. MOTOR CHARACTERISTICS
SERIES MOTOR
1.Armature Torque and armature current i.e.,Ta /Ia characteristics. It is known as electrical characteristics.
2. Speed and armature current i.e, N/Ia Characteristics
3. Speed and armature torque i.e, N/Ta Characteristics. It is known as mechanical characteristics.
Voltage Equation, V=Eb+Ia(Ra+Rse)+Vbrush 1 2 3

7. SHUNT MOTOR
1.Armature Torque and armature current i.e.,Ta /Ia characteristics
2.Speed and armature current i.e.,N /Ia characteristics
3. Speed and Armature Torque i.e.,N /Ta characteristics
Voltage Equation, V=Eb+IaRa+Vbrush 2 3 1 2

8. Cummulatively compound Differentially compound
COMPOUND MOTOR
Cummulatively compound
Differentially compound
Long shunt compound motor, V=Eb+Ia(Ra+Rse)+Vbrush
Short Shunt compound motor, V=Eb+IaRa+IseRse+Vbrush

9. COMPOUND MOTOR Speed and Armature current, i.e N/Ia characteristics
Armature torque and Armature current, i.e Ta/Ia characteristics 2 1

10. APPLICATIONS OF DC MOTOR
Shunt Motor:
Its an constant speed motor.
Where the speed is required to remain almost constant from no load to full load.
Industrial use: Lathes, drills, boring mills, shapers, spinning machine, etc.,
Series Motor:
Its an variable speed motor.
Where large starting torque is required.
Where the load is subjected to heavy fluctuations and the speed is automatically required to reduce at high torque and vice versa.
Industrial Use: Electric traction, cranes, elevator, air compressor, vacuum cleaner, hair drier, etc.,
Compound Motor:
Differential Compound motors are rarely used because of their poor torque characteristics. However, cummulative compound motors are used where constant speed is required with irregular loads (or) suddenly applied heavy loads.
Industrial Use: Presses, reciprocating machines, etc.,

11. GENERATOR CHARACTERISTICS
APPLICATIONS OF DC GENERATOR
Shunt generators-Charging of car batteries, supplying fields of synchronous machines.
Series generators used as boosters for adding a voltage to the transmission line and to compensate the voltage drop.
Compound generators to maintain better voltage regulation
GENERATOR CHARACTERISTICS
The three most important characteristics or curves of a d.c generator are
1. No-load saturation characteristic (E0/If) 2. Internal or Total characteristic (E/Ia)
3. External characteristic (V/I)

12. SERIES GENERATOR:
Genereted, Eg=V+Ia(Ra+Rse)+Vbrush

13. SHUNT GENERATOR:
Genereted, Eg=V+IaRa+Vbrush

14. COMPOUND GENERATOR:
Long shunt compound motor, Eg=V+Ia(Ra+Rse)+Vbrush
Short Shunt compound motor, Eg= V+IaRa+IseRse+Vbrush

15. SPEED CONTROL OF DC MOTOR
1.Shunt Motor
Flied (or) Flux control method
Armature control method
Voltage control method
Multiple voltage control method
Ward Leonord method
2. Series Motor
Flux control method
Field divertor
Armature divertor
Tapped field control method
Paralleling field coils
Variable resistance in series with armature

16. TRANSFORMER CONSTRUCTION

17. Transformer is a static piece of apparatus is used to transfer the a
Transformer is a static piece of apparatus is used to transfer the a.c power from one circuit (primary) to another (secondary) circuit without any change in frequency and only desirable change in voltage and current.

18. Classification of Transformer:
Duty they perform
Power transformer – for transmission and distribution purpose
Current transformer – instrument transformer
Potential transformer – instrument transformer
2. Construction
Core type transformer
Shell type transformer
Berry core type transformer
3. Voltage output
Step down transformer
Step up transformer
Auto transformer
4. Application
Welding transformer
Furnace transformer

19. 5. Cooling
Duct type transformer
Oil immersed
Self cooled
Forced air cooled
Water cooled
Forced oil cooled
6. Input supply
Single phase transformer
Three phase transformer
Star-star
Star-Delta
Delta-delta
Delta-star
open delta
scott connection

20. CORE TYPE TRANSFORMER
SHELL TYPE TRANSFORMER
CONSTRUCTION OF TRANSFORMERS:

22. EQUIVALENT CIRCUIT OF TRANSFORMER:‘

23. TYPES OF LOSSES IN TRANSFORMER:
1.Core loss (or) Iron loss
a. Hysteresis loss
b. Eddy current loss
2. Copper loss
3. Stray loss
4. Dielectric loss

25. DOUBLE REVOLVING FIELD THEORY

26. Torque-Speed Characteristics:

27. Single Phase Induction Motor
stator

28. Squirrel cage rotor

29. SINGLE PHASE INDUCTION MOTOR
The single phase induction motor are classified according to the starting methods,
Resistance start (split phase) induction motor
Capacitor start induction motor
Capacitor run induction motor
Capacitor start capacitor run motor
Shaded pole induction motor

30. RESISTANCE START (SPLIT PHASE) INDUCTION MOTOR
Phasor Diagram

31. SPEED-TORQUE CHARACTERISTICS

32. APPLICATIONS
It is mainly used for loads that require low or medium starting torque. The applications are
Fans
Blowers
Centrifugal Pumps
Washing Machines

33. CAPACITOR START INDUCTION MOTOR
PHASOR DIAGRAM

34. SPEED-TORQUE CHARACTERISTICS

35. APPLICATIONS
It is mainly used for high starting loads. The applications are
Compressor
Pumps
Conveyors
Refrigerators
Air Conditioning Equipments
Washing Machines

36. CAPACITOR RUN INDUCTION MOTOR

37. SPEED-TORQUE CHARACTERISTICS

38. ADVANTAGES
High power factor at full load
High full load efficiency
Increased pull out torque
Low full load line current
APPLICATIONS
Fans
Blowers
Centrifugal Pumps

39. CAPACITOR START CAPACITOR RUN MOTOR

40. SPEED-TORQUE CHARACTERISTICS

41. ADVANTAGES
High starting torque
High efficiency
High power factor
APPLICATIONS
It is mainly used for low noise and high starting torque applications, such as
Compressors
Pumps
Conveyors
Refrigerators

42. SHADED POLE INDUCTION MOTOR

44. SPEED-TORQUE CHARACTERISTICS

45. DISADVANTAGES
Low efficiency
Low power factor
Very low starting torque
APPLICATIONS
The main applications of these motors are for load requiring low starting torque such as
Fans
Blowers
Turn tables
Hair driers
Motion picture projectors