This document provides an overview of DC machines including their history, evolution, basic construction, and how they work. It discusses the key components of a DC machine such as the yoke, poles, armature, field and armature windings, commutator, and brushes. It also covers Fleming's rule, the two types of armature windings, how a DC motor works by creating a magnetic field to rotate the rotor, different types of DC motors including brushed and brushless, and their applications. Losses in DC motors and generators are also briefly discussed.

1. Overview of DC Machines

2. Contents
• History
• Evolution of Motors
• What is a DC Machine?
• Basic Construction
• How DC Motor works?
• Fleming’s Rule

3. History
• A DC motor is any class of rotary electrical motors that converts direct current
electrical energy into mechanical energy. The history of DC motors goes as far
back as the 19th century. In 1832, a British scientist, William Sturgeon, created
the first DC motor that had the ability to power machinery.
• Very advanced mechanisms are developed in the middle ages.
• Development of the steam engine leads to the industrial revolution in the mid
1700’s.
• Michael Faraday runs the first electric motor experiments in 1821.

4. Evolution of Motors

5. What is a DC Machine?
• A DC machine is an electromechanical device that is used to convert electrical energy into
mechanical energy or vice versa.
• The DC machine used to convert electrical energy into mechanical energy, which is known as
DC motor and the DC machine used to convert mechanical energy into electrical energy, which
is known as DC generator. The same machine can be used either as a motor or generator. The
construction is same for DC motor and DC generator.
• It works on the principle of Lorentz Law, which states that the current carrying conductor
placed in a magnetic and electric field experience a force.

6. Basic Construction
Steel Yoke - the yoke is also known as the
frame. It covers the internal parts of the
machine. The yoke is made up of low
reluctance magnetic material like iron and
silicon steel.
Poles - the field winding is placed on a pole.
When current passes through the field
winding, it will create an electric magnetic
field and behaves as an electromagnet. The
pole shoes expand flux in the entire
machine. To reduce the eddy current
losses, the pole and pole shoes are
laminated. The pole shoes are used to
provide support to the field winding and
not to slip from the pole.
Armature - the armature core is cylindrical
in shape and connected by a key with the
shaft. So, it is a rotating part of the DC
machine. The armature core consists of a
number of slots on its outer periphery. It is
made up of low reluctance and high
permeability material like cast iron or cast
steel.
Field Winding - it is winding wounded on
the pole is known as the field winding.
External DC source or the output of the
machine is used to excite the field winding.
When DC current passes through the coil, it
will generate the electromagnetic field
(EMF). And it will magnetize the pole and
produce the magnetic flux. The flux
produced by the pole is directly
proportional to the field current. And flux
is more enough to cross the air gap
between armature and pole shoes.
Armature Winding - the armature winding
is placed on the slots of the armature core.
It is made up of copper. The armature
winding links with the magnetic flux and
induce a rotating magnetic flux.
Carbon Brush - the commutator connected
the external circuit via brushes. The
brushes are used to carry current from the
armature conductors.
Commutator- the commutator or also
known as mechanical rectifier is used to
connects the rotating armature conductor
with a stationary external circuit.

7. Two Types of Armature Windings
• Lap winding
In lap winding, the armature conductors are divided into groups of a number of poles
P. All conductor groups are connected in parallel and in one group, all conductors are
connected in series.
For lap winding, the number of a parallel path (A) is the same as the number of poles (P).
Therefore, in lap winding, the number of parallel paths is more. And due to this, it is capable
of supplying larger load current.
So, lap winding is used for low voltage high current applications.
• Commutator
The commutator is mounted on the shaft of a machine. The armature conductors
are rotating. The commutator is used to connects the rotating armature conductor with a
stationary external circuit.
It converts alternating torque produced in the armature into unidirectional torque. In
other words, it converts AC torque into DC torque. So, it works similar to the rectifier.

8. How DC Motor works?
• The rotor is normally located on the
inside of the motor, while the stator
is located on the outside. The rotor
contains coil windings that are
powered by the DC current and the
stator contains either permanent
magnets or electromagnetic
windings. When the motor is
powered by DC current, a magnetic
field is created within the stator,
attracting and repelling the magnets
on the rotor. This causes the rotor to
start rotating. To keep the rotor
rotating, the motor has a
commutator. When the rotor aligns
with the magnetic field, it would stop
spinning, but in this case the
commutator would reverse the
current through the stator and this
way reverse the magnetic field. This
way the rotor can keep spinning.

9. Force = Magnetic flux density x
current x length of wire
F = B x I x L
Where:
F = Magnitude of the
generated force, N (Newton)
B = Flux density, T (Tesla)
I = Current, A (Ampere)
L = Length of the conductor, m
(meter)

10. Is DC motor same as DC generator?
• A dc motor is a machine powered by electricity to produce mechanical energy. A
dc generator is a machine powered by mechanical energy to produce
electricity. A dc motor and a dc generator are the two sides of the same coin.
Do power tools use DC motors?
• There are two main types of motors used in most applications: DC (or universal)
motors and induction motors. DC motors are much easier to understand, so I will
start with those. Universal motors are used in most hand held power tools, such
as drills, routers, jigsaws and sanders.

11. Types of DC Motors
• DC motors fall into different categories, depending on their construction. The
most common types include brushed or brushless, permanent magnet, series,
and parallel.
Brushed Motors Brushless Motors
• The brushed DC electric
motor generates torque directly from
DC power supplied to the motor by
using internal commutation, stationary
magnets(permanent or electromagnet
s), and rotating electromagnets.
Brushes are usually made of graphite or
carbon, sometimes with added
dispersed copper to improve
conductivity.
• Typical brushless DC motors use one or
more permanent magnets in the rotor
and electromagnets on the motor
housing for the stator. A motor
controller converts DC to AC. The
motor controller can sense the rotor's
position via Hall effect sensors or
similar devices and can precisely
control the timing, phase, etc., of the
current in the rotor coils to optimize
torque, conserve power, regulate
speed, and even apply some braking.

12. Applications of Brushed DC Motors
• These motors still use for industrial purposes for both low and high power, fixed
and variable speed electric drives. They still use for paper machines, cranes,
electrical propulsion, sewing machines, power tools, and steel rolling mills.

13. Applications of Brushless DC Motors
• Brushless motors are a great way to keep drones airborne. But where else can
brushless motors be used? From underwater mapping for marine applications to
PAP respirators for medical uses.

14. Add a Slide Title - 2
Dc motor LOSES
• What are the losses in motor?
• Intrinsic losses are of two
types: fixed losses - independent of
motor load, and variable losses -
dependent on load. Fixed losses
consist of magnetic core losses and
friction and windage losses.
Magnetic core losses (sometimes
called iron losses) consist of eddy
current and hysteresis losses in the
stator.
Dc generator loses

15. Different types of DC MOTORS

17. Add a Slide
Title - 4

18. Add a Slide
Title - 5