The document provides an overview of DC machines, detailing their construction, components such as yoke, poles, field winding, armature, commutator, and brushes, as well as working principles and applications. It explains the types of DC motors including shunt, series, and compound, along with their operational characteristics and starter types. Key concepts include torque, electromotive force (emf), and specific applications for different motor types in industrial settings.

2. DC MACHINES

3. OBJECTIVES
1)BASIC FUNDAMENTAL OF MACHINE
2)APPLICATION OF MACHINE

5. Construction Of A DC Machine:
4-pole DC machine.

6. • Important parts of DC motor:
1. Yoke 4. Armature
2. Field winding 5. Commutator, brushes &
gear
3. poles 6. Brushes
1. Yoke:
 It acts as the outer support of a DC motor.
 It provides mechanical support for the poles.

7. 2. Poles:
pole of a dc motor is an electromagnet.
The field winding is wound over the poles.
Poles produces magnetic flux when the filed
winding is excited.
3. Field winding:
 The coils wound around the pole are called
field coils and they are connected in series with
each other to form field winding.
 When current passing through the field
winding, magnetic flux produced in the air gap
between pole and armature.

8. Field winding

9. 4. Armature:
Armature is a cylindrical drum mounted on shaft
in which number of slots are provided.
Armature conductors are placed in these slots.
Theses armature conductors are interconnected to
form the armature winding.

10. Armature winding
There are 2 types of winding
Lap and Wave winding
Lap winding
A = P
The armature
windings are
divided into
no. of sections
equal to the no
of poles
Wave winding
A = 2
It is used in low
current output
and high voltage.
2 brushes

11. 5. Commutator:
A commutator is a cylindrical drum mounted on
the shaft along with the armature core.
It collects the current from the armature
conductors and passed it to the external load via
brushes.

12. 6. Brushes:
 Commutator is rotating. So it is not possible to connect
the load directly to it.
 Hence current is conducted from the armature to the
external load by the carbon brushes which are held
against the surface of commutator by springs.
Carbon brushes are used in DC machines because they are
soft materials
It does not generate spikes when they contact commutator
Carbon is used for brushes because it has negative
temperature coefficient of resistance

14. Windings in DC Machine
• In any dc machines, there are two windings:
1. Field winding 2. Armature winding
• Out of these, the field winding is stationary
which does not move at all and armature
winding is mounted on a shaft. So it can rotate
freely.
• Connection of windings for operation as motor:
 To operate the dc machine as a motor, the field
winding and armature winding is connected
across a dc power supply.

15. Working principle
A motor works on the principles of Faraday’s law of
electromagnetic induction.
Whenever a conductor is moved in the magnetic field
, an emf is induced and the magnitude of the induced
emf is directly proportional to the rate of change of flux
linkage.
This emf causes a current flow if the conductor
circuit is closed .

17. Fleming’s Right hand rule

19. EMF equation
Let,
Ø= flux per pole in weber
Z = Total number of conductor
P = Number of poles
A = Number of parallel paths
N =armature speed in rpm
Eg = emf generated in any on of the
parallel path

20. EMF equation
Flux cut by 1 conductor
in 1 revolution = P * φ
Flux cut by 1 conductor in
60 sec = P φ N /60
Avg emf generated in 1
conductor = PφN/60
Number of conductors in
each parallel path = Z /A
Eg = PφNZ/60A

21. Torque
The turning or twisting force about an
axis is called torque .
P = T * 2 πN/ 60
Eb Ia = Ta * 2 πN/ 60
T ∞ φ I a
Ta ∞ I2a

22. DC Shunt Motor
• In DC shunt type motor, field and armature
winding are connected in parallel as shown in
fig. and this combination is connected across a
common dc power supply.

23. DC Series Motor
• In DC series motor, the armature and field
windings are connected in series with each
other.
∴ ø ∝ Ia
∴ ø ∝ Is

24. DC Compound Motor
Fig.(1): Long shunt compound dc motor fig.(2):Short shunt compound dc motor

26. Starters for DC motors
Needed to limit the starting current .
1. Two point starter
2. Three point starter
3. Four point starter

27. Applications:
Shunt Motor:
Blowers and fans
Centrifugal and reciprocating pumps
Lathe machines
Machine tools
Milling machines
Drilling machines

28. Series Motor:
Cranes
Hoists , Elevators
Trolleys
Conveyors
Electric locomotives
Applications:

29. Cumulative compound Motor:
Rolling mills
Punches
Shears
Heavy planers
Elevators
Applications:

30. Applications:
Shunt Motor:
Blowers and fans
Centrifugal and reciprocating pumps
Lathe machines
Machine tools
Milling machines
Drilling machines

31. Series Motor:
Cranes
Hoists , Elevators
Trolleys
Conveyors
Electric locomotives
Applications:

32. Cumulative compound Motor:
Rolling mills
Punches
Shears
Heavy planers
Elevators
Applications:

43. APPLICATION
Used for the loads which require a
gradual buildup of torque. Used for
the loads that require speed control.
The wound rotor induction
motors are used in conveyors, cranes,
pumps, elevators and compressors.

44. Synchronous Motor

45. It is used where high power at low speed
is required. Such as rolling mills, chippers,
mixers, pumps, pumps, compressor etc.