The document discusses the principles and components of DC motors. It begins by explaining that a DC motor converts electrical energy to mechanical energy using electromagnetic forces generated when a current-carrying conductor is placed in a magnetic field. It then describes the Lorentz force equation and how it relates to the operation of DC motors. The document goes on to define the back EMF produced in a DC motor and its significance. It provides histories of early electric motors and inventors. It also classifies DC motors, describes the functions of their main components like the yoke and field coils, and gives examples of applications for different DC motor types.

2. PRINCIPLE of D.C MOTOR
An Electric motor is a machine which converts
electric energy into mechanical energy
Its action is based on the principle that when
a current carrying conductor is place in magnetic
field , it experiences a mechanical force whose
direction is given by FLEMING’s left hand rule
(F=Bil sinØ) & LORENTZ force

4. Lorentz force
The force which is exerted by a magnetic field on a
moving electric charge is called lorentz force
dF = dq(E+vB)
for the operation of
D.C motor ,consider E=0
dF=dq*v*B
w.k.t v=dL / dt
Where dL is length of
Conductor carrying charge ‘q’ i.e., dF=dq*dL/dt*B
dF=I*dL*B F=BIL sinØ

5. Significance of back EMF
What is Back EMF ?
When the armature of a d.c. motor rotates under the
influence of the driving torque, the armature conductors
move through the magnetic field and hence e.m.f. is
induced in them as in a generator. The induced e.m.f. acts
in opposite direction to the applied voltage V (Lenz’s law)
and in known as back or counter e.m.f. Eb.
The back emf Eb(= PΦZN/60 A) is always less than the
applied voltage V, although this difference is small when
the motor is running under normal conditions.

6. INTERNAL WORKING

7. HISTORY of MOTORS
With the invention of the battery (Allessandro Volta,
1800; produces a continuous electrical power as
opposed to a spark or static electricity, from a stack of
silver and zinc plates ).
The generation of a magnetic field from
electric current (Hans Christian
Oersted, 1820 finds the generation of a
magnetic field by electric currents by
observation of the deflection of a
compass needle. This was the first time a
time a mechanical movement was
caused by an electric current.)
ALLESSANDRO VOLTA
ORESTED

8. HISTORY of MOTORS
In 1821,
Michael Faraday (British) creates two
experiments for the
demonstration of electromagnetic
rotation. A vertically suspended wire
moves in a circular orbit around
a magnet.
Later in 1825, William Sturgeon (British)
invents the electromagnet, a coil of wires
with an iron core to enhance the magnetic
field. This foundation for building electric
motors was laid.
FARADAY
STURGEON

9. HISTORY of MOTORS
The first rotating device driven by
electromagnetism was built by
the Englishman Peter Barlow in 1822
(Barlow's Wheel).
1834 - Thomas Davenport of Vermont
developed the first real electric motor
('real' meaning powerful enough to do a task)
although Joseph Henry and Michael Faraday
created early motion devices using
electromagnetic fields.
ELECTRIC MOTOR

10. CONTRUCTION OF D.C MOTOR

11. Main classification of D.C Motors
Brushless D.C motors
A DC Brushless Motor uses a
permanent magnet external rotor, three
phases of driving coils, one or more Hall
effect devices to sense the position of
the rotor, and the associated drive
electronics
HALL EFFECT: the production of a
potential difference across an electrical
conductor when a magnetic field is
applied in a direction perpendicular to
that of the flow of current.
Brushed D.C motors
A Brushed Motor has a rotating set of
wound wire coils called an armature
which acts as an electromagnet with
two poles.

12. Pros & cons of Brushless D.C motor
BLDC Motor Pros
 Electronic commutation based on Hall position sensors
 Less required maintenance due to absence of brushes
 Speed/Torque- flat, enables operation at all speeds with rated load
 High efficiency, no voltage drop across brushes
 High output power/frame size.
Reduced size due to superior thermal characteristics. Because BLDC has the windings on the
stator, which is connected to the case, the heat disipation is better
 Higher speed range - no mechanical limitation imposed by brushes/commutator
 Low electric noise generation
BLDC Motor Cons
 Higher cost of construction
 Control is complex and expensive
 Electric Controller is required to keep the motor running.
It offers double the price of the motor
BRUSHLESS MOTOR

13. Pros & cons of Brushed D.C motor
Brushed Motor Pros
 Two wire control
 Replaceable brushes for extended life
 Low cost of construction
 Simple and inexpensive control
 No controller is required for fixed speeds
 Operates in extreme environments due to lack of electronics
Brushed Motor Cons
 Periodic maintenance is required
 Speed/torque is moderately flat. At higher speeds, brush fric
increases, thus reducing useful torque
 Poor heat dissipation due to internal rotor construction
 Higher rotor inertia which limits the dynamic characteristics
 Lower speed range due to mechanical limitations on the
brushes
 Brush Arcing will generate noise causing EMI

14. Function of each part of DC Motor
Yoke:
 It is outer cover of dc motor also called as frame.
 It provides protection to the rotating and other part of
the machine from moisture, dust etc.
 Yoke is an iron body which provides the path for the
flux to complete the magnetic circuit.
 It provides the mechanical support for the poles.
 Material Used: low reluctance material such as cast
iron, silicon steel, rolled steel, cast steel etc

15. Function of each part of DC Motor
field coil wound on pole
Field winding :
 The coil wound on the pole core are called field coils.
 Field coils are connected in series to form field
winding.
 Current is passed through the field winding in a
specific direction, to magnetize the poles and pole
shoes. Thus magnetic flux is produce in the air gap
between the pole shoe and armature.
 Field winding is also called as Exciting winding.
 Material Used for copper conductor is copper.
 Due to the current flowing through the field winding
alternate N and S poles are produced.

16. Classification of electric motors

17. Classification of electric motors

18. Types of Brushed D.C Motor

19. Applications of separately excited
motors
 Electric traction( in train)
 servomotor
 load carrying vehicles like e-rickshaw

20. Application of D.C series Motor
 Traction system
 Cranes
 Air compressors.

21. Applications of DC Shunt Motor
 Lathe Machines (used to rotate work piece)
 Centrifugal Pumps
 Fans
 Blowers
 Conveyors
 Lifts
 Weaving Machine
 Spinning machines, etc.
Lathe machine
conveyors
Spinning machine

22. Applications of DC Compound
Motors
 Presses
 Shears
 Conveyors
 Elevators
 Rolling Mills
 Heavy Planners, etc.
presses
elevators
Rolling mills

23. Any queries???