Joke of the day: An object at rest stays at rest and an object
in motion stays in motion with the same speed and in the same
direction unless acted upon by an unbalanced force.
Slide 3
Direct Current Electric Motor An electric motor converts
electrical energy into mechanical energy An electromagnet is the
basis of an electric motor A motor uses magnets to create motion.
Opposites attract and likes repel. Inside an electric motor, these
attracting and repelling forces create rotational motion. Direct
current (DC) means the electrical current is flowing in only one
direction in a circuit. Batteries are a good source of direct
current (DC).
Slide 4
The basics: STATOR ROTOR An electric motor has two basic parts:
The stationary part (external magnets, power source, brushes) The
rotating part of the electric motor is called the rotor.
Slide 5
Parts (and function) of a DC motor: 1. DC power supply 2. Rotor
(armature) 3. Commutator 4. Brushes 5. External magnets
Slide 6
Slide 7
1. DC Power Supply Aka battery To provide the current
Slide 8
2. Rotor (Armature) the revolving structure wound with the
coils that carry the current moves under the influence of a
magnetic field
Slide 9
Diagram: Spinning Armature
Slide 10
3/4. Commutator and brushes Commutator is simply a pair of
plates attached to the end of the rotor These plates provide the
two connections for the coil The brushes are attached to the leads
from the power supply Commutator and brushes work together to let
current flow from the power supply to the electromagnetic coil when
they make contact with each other
Slide 11
Brushes attached to battery Commutator attached to rotor
Slide 12
5. Magnets Provides the external magnetic field Used to create
a net rotational movement
Slide 13
A key component of motors: Torque Torque is a measure of how
much a force acting on an object causes that object to rotate. The
object rotates about an axis or pivot point
Slide 14
Torque Torque is the cross product of radius and force The
units are Nm The direction is positive for ccw and negative for
cw
Slide 15
Torque on a Current Carrying Loop In a motor.
Slide 16
Slide 17
Video clip: http://www.youtube.com/watch?v=Ue6S8L4On-Y
Slide 18
Build some simple motors!
Slide 19
While both A.C. and D.C. motors serve the same function of
converting electrical energy into mechanical energy, they are
powered, constructed and controlled differently. 1 The most basic
difference is the power source. A.C. motors are powered from
alternating current (A.C.) while D.C. motors are powered from
direct current (D.C.), such as batteries, D.C. power supplies or an
AC-to-DC power converter. D.C wound field motors are constructed
with brushes and a commutator, which add to the maintenance, limit
the speed and usually reduce the life expectancy of brushed D.C.
motors. A.C. induction motors do not use brushes; they are very
rugged and have long life expectancies. The final basic difference
is speed control. The speed of a D.C. motor is controlled by
varying the armature windings current while the speed of an A.C.
motor is controlled by varying the frequency, which is commonly
done with an adjustable frequency drive control. 2 Published by
Ohio Electric Motors:
http://www.ohioelectricmotors.com/what-is-the-
difference-between-an-ac-motor-and-a-dc-motor-673#ixzz2PFxVRFMG 1
2http://www.ohioelectricmotors.com/what-is-the-
difference-between-an-ac-motor-and-a-dc-motor-673#ixzz2PFxVRFMG