The document provides an overview of DC machines, focusing on their principles, construction, and operational mechanisms, particularly emphasizing components such as the armature, field windings, and the impact of back electromotive force. It details different types of DC motors, including shunt, series, and compound motors, and outlines their applications in various industrial scenarios. Additionally, it describes the need for starters to limit the starting current in DC motors along with some specifications for a typical DC series motor.

1. BASICS OF MACHINE
Present by- Mrs.Prashant Raghuwanshi
Assistant Professor EE Department

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

9. Fleming’s Right hand rule

10. Electric Machine

12. Image Of DC Machine

14. DC MACHINES

15. DC Motor Principle
A machine that converts dc power into
mechanical energy is known as dc motor.
Its operation is based on the principle that
when a current carrying conductor is placed in
a magnetic field, the conductor experiences a
mechanical force. The direction of the force is
given by Fleming’s left hand rule. its
magnitude is given by F = BIL Newton.

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

21. Yoke:
 It acts as the outer support of a DC motor.
 It provides mechanical support for the poles.

23. 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.
 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.

25. Field winding

26. 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.

29. 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.

31. 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

33. 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 .

37. 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

38. 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

39. Armature torque (Ta)
The power developed in the armature can be given as,
Pa = Ta × ω = Ta × 2πN/60
The mechanical power developed in the armature is
converted from the electrical power,
Therefore, mechanical power = electrical power
That means, Ta × 2πN/60 = Eb.Ia
We know, Eb = PΦNZ / 60A
Therefore, Ta × 2πN/60 = (PΦNZ / 60A) × Ia
Rearranging the above equation,
Ta = (PZ / 2πA) × Φ.Ia

40. 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
∞

41. • What is Back E.M.F. in DC Motor :
When the armature of a d.c. motor rotates, the the
windings or conductors on armature also rotate in the
magnetic field. According to the " Faraday's Laws of
Electro-Magnetic Induction " e.m.f. is induced in the
conductors, whose direction, as found by " Fleming's Rule
", is in opposition to the applied voltage. The emf induced
in the armature winding is in opposite direction, hence it
is referred to as back e.m.f. Eb of the motor. This back emf
tries to oppose applied voltage V ,but it has to drive
armature current Ia against the opposing of back emf Eb.

42. Where Ra = armature resistance

43. Induced e.m.f or Back e.m.f.,
Back e.m.f. depends upon armature speed. If speed is high Eb
is
high and hence Ia
is small. If speed is less, the Eb
is less, hence
more current flows to develop torque.

44. 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.

45. • Armature Winding is the windings, in which
voltage is induced.The Field Winding is the
winding in which the main field flux is
produced when the current through the
winding is passed. Some of the basic
terms related to the Armature Winding are
defined as follows:

46. Turn: A turn consists of two conductors connected to one end
by an end connector.
Coil: A coil is formed by connecting several turns in the series.
Winding:
symbol (S) meaning Start , symbol (F) meaning Finish.
The figure of the turn is shown below.

47. The figure of the coil is shown below.

48. The figure of the winding is shown below.

50. • Lap winding is the winding in which successive coils
overlap each other. It is named “Lap” winding because
it doubles or laps back with its succeeding coils.

51. • In this winding the finishing end of one coil is
connected to one commutator segment and the
starting end of the next coil situated under the
same pole and connected with same
commutator segment.
•
Here we can see in picture, the finishing end of
coil – 1 and starting end of coil – 2 are both
connected to the commutator segment – 2 and
both coils are under the same magnetic pole
that is N pole here.

52. • Wave winding is one type of
armature winding. In this winding, we
connect the end of one coil to the starting of
another coil of the same polarity as that of the
first coil. In this type of winding the coil side
(A – B)

55. 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

56. Types of DC Motors
• Depending on the way of connecting the
armature and field windings of a d.c. motors
are classified as follows:
DC Motor
DC series
motor
Shunt motor Compound
motor
Separately
excited motor
Short shunt
compound
Long shunt
compound

57. 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.

58. IL = Ia + Ish
Ish = V / Rsh
V = Eb + Ia Ra +
BCD
Where
BCD = brush contact drop ( usually 1V
/ brush )
Ra = armature ( winding ) resistance

59. • The resistance of shunt field winding (Rsh) is always much higher
than that of armature winding (Ra).
• This is because the number of turns for the field winding is more
than that of armature winding.
• The field current Ish always remains constant. Since V and Rsh both
are constant. Hence flux produced also remains constant. Because
field current is responsible for generation of flux.
∴ ø I
∝ sh
• This is why the shunt motor is also called as the constant flux
motors.

60. IL = Ise Rse = Ia
V = Eb + Ise Rse + Ia Ra + BCD
= Eb + Ia (Rse + Ra ) + BCD
DC Series Motor
In DC series motor, the armature and field
windings are connected in series with each
other.

61. • The resistance of the series field winding (Rs)
is much smaller as compared to that of the
armature resistance (Ra).
• The flux produced is proportional to the field
current. But in series motor, the field current is
same as armature current.
∴ ø I
∝ a or
∴ ø I
∝ s

62. • The armature current Ia and hence field current
Is will be dependent on the load.
• Hence in DC series motor the flux does not
remains constant.
Fig.(1):DC series motor schematic diagram

63. DC Compound Motor
1. Long Shunt Compound Motor:
• In long shunt dc motor, shunt field winding is connected across
the series combination of the armature and series field winding.
2. Short Shunt Compound Motor:
• In short shunt compound motor, armature and field windings
are connected in parallel with each other and this combination
is connected in series with the series filed winding.
 The long shunt and short shunt compound motors are further
classified as cumulative and differential compound motors

64. Short Shunt Compound Motor :
It is combination of shunt and series. But, shunt winding is
connected across armature only. Hence short shunt motor.

65. Ise = Ia
IL = Ise + Ish = Ia + Ish
Ish = V / Rsh
V = Eb + Ise Rse + Ia Ra + BCD
Long Shunt Compound Motor :
The shunt winding is connected across the combination of armature
and series fields. Hence know as long shunt compound motor.

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

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

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

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

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

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

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

74. • Typical specifications of DC series motor:
Sr.
No.
Specifications/Rating Value
1. Output power in horse power 3HP
2. Rated voltage 230V
3. Type of field winding Series
4. Excitation voltage 230V
5. Insulation B
6. Base speed 1000RPM
7. Current 11Amp
8. Frame size 132 S
9. Rating Continous
10. S.R.Number 840858

75. THANK YOU