DC motors convert electrical energy into mechanical motion using either AC or DC power sources, producing rotational or translational movement of the output shaft based on specified load limits. Their selection depends on application characteristics such as speed, weight, size, cost, and control accuracy, with performance described through parameters like rated speed, torque, and horsepower. The principle of operation involves electrical currents generating magnetic fields that induce torque, causing rotation as the armature interacts with fixed magnetic fields.

1. DC MOTORS

2.  Motors convert electric energy to
mechanical motion.
Either an AC or DC electrical energy source
serves as the input to the motor.
The result is mechanical motion of the output
shaft, that is a rotation about or a translation
along the shaft, provided the load carried by
the shaft does not exceed the maximum load
the motor is designed to carry.

3. There are numerous ways to design a motor, thus
there are many different types of motors.
The type of motor chosen for an application
depends on the characteristics needed in that
application.
These include:
◦How fast you want the object to move,
◦The weight, size of the object to be moved,
◦The cost and size of the motor,
◦The accuracy of position or speed control
needed.

4. The level of performance a motor can provide is
described by its parameters. These include:
Rated Speed
◦Speed measured in shaft revolutions per minute
(RPM)
Torque
◦Rotational force produced around a given point,
due to a force applied at a radius from that point,
measured in lb-ft (or, oz-in).
HorsePower = Speed x Torque / 5252.11...
◦A measure of work expended: 1 HP = 33,000 foot-
pounds per minute.
Torque-Speed performance of a motor

5.  Electric Motors or Motors convert electrical energy to mechanical
motion
 Motors are powered by a source of electricity – either AC or DC.
 DC Electric Motors use Direct Current (DC) sources of electricity:
◦ Batteries
◦ DC Power supply
 Principle of How Motors Work:
 Electrical current flowing in a loop of wire will produce a magnetic
field across the loop.
When this loop is surrounded by the field of another magnet, the loop
will turn, producing a force (called torque) that results in mechanical
motion.
• Inside a motor we find:
Permanent magnets,
Electro-magnets,
Or a combination of the two.

6. When current moves through a conductor a circular
magnetic field is induced around the conductor
Magnetic Field Lines
Negative Battery
Terminal
Positive Battery
Terminal

7. The Right Hand Rule
The direction of the magnetic field
surrounding the conductor can
be found using your
right hand
Position the thumb of your right hand
pointing in the direction of
conventional current (Positive to
Negative) and your fingers will wrap
around the conductor in the direction
of the induced magnetic field.

8. When current moves through a coiled conductor a
circular magnetic field is induced about the coil and
becomes an electromagnet.
Current and Magnetism in a Coil

9. Motor (armature) rotation is caused by the simultaneous
attraction and repulsion between the electromagnetic
field in the armature and a fixed magnetic field
Fixed Magnets
Armature

10. Induced Magnetic Field
(Due to current)
Fixed Magnetic Field
Force
A Conductor in a Fixed
Magnetic Field
A Current Carrying Conductor
in a Fixed Magnetic Field

11. N
S
A Motor Armature in a Fixed
Magnetic Field
The magnetic field surrounding a current
carrying conductor interacts with an
existing magnetic field.
Direction of Force (Torque) acting
to turn the Armature (Conductor)

12. Fleming's Left Hand (Motor) Rule
Determines the direction of DC current
carrying conductor in a fixed magnetic field
Thumb = Direction of
Conductor Motion Fore Finger = Direction of
Fixed Magnetic Field (N to S)
Middle Finger =
Conventional
Current Direction

13. Fleming's Left Hand (Motor) Rule
N
S
Direction of Rotation
Fixed Magnetic Field Direction
Conventional
Current Direction

14. N
S
N
S Use the Left Hand Rule to
Determine the Rotation
Direction of the Armatures
in A and B
Notice that when the
current through the
armature is reversed,
it moves (Rotates) in
the opposite direction
A
B
Hint: You will have to turn
your left hand upside down
for example A

15. Magnetic Forces Acting on Parallel
Current Carrying Conductors
X
Two parallel
conductors
carrying currents
in opposite
directions will
repel each other,
and they will set
up a polarized
magnetic field
between
themselves.
North
South

16. Magnetic Forces Acting on Parallel
Current Carrying Conductors
X
South
North
South
North
Wrapping current carrying conductors around
an iron core creates an electro magnet

17. The Armature of a Brush Commutated DC
Motor is made up of Current Carrying
Conductors Wrapped Around an Iron Core
The Motor Armature is an electro Magnet and
Operates according to the Principles Described in
this Slide Show

18. The End