Transcript BEX – Basic Electricity

BEX – Basic Electricity – Unit 13
Magnetic Motors
REF: Delmar’s Standard Textbook of Electricity, Unit 13
Magnetic Motors
Lesson Objectives:
To understand the principles of magnetism
as it applies to magnetic motors
To identify the different types of motors
To identify the various components of an
electromagnetic motor
Magnetic Motors
Magnetic properties
Unlike poles attract
Like poles repel
The basis for the
operation for a motor
Magnetic Motors
Magnetic properties
Current flow through a
conductor creates a weak
magnetic field
Wrapping a conductor
increases the magnetic field
Magnetic Motors
Magnetic Properties
When a current carrying
conductor is placed inside
of a magnetic field, the
conductor moves towards
the weaker magnetic field
on the outside of the
magnet
Magnetic Motors
Components
Magnetic Motors
A Simple Electromagnetic Motor
Armature windings
Field windings
Pole shoes
Brushes
Commutator
Power source
Magnetic Motors
Field Coils & Pole Shoes:
Heavy copper wire wrapped in a coil
Surrounding an iron core
Forms an electromagnet
Magnetic Motors
The Armature:
Rotates within stationary field coils
Consists of heavy loops of insulated copper wire
Wraps around (and insulated from) a laminated
iron core
Magnetic Motors
The Commutator:
A series of split ring copper segment bars
Forms a sliding contact area for brushes
Magnetic Motors
The Brushes:
Made of a mixture of carbon and copper
Used to conduct high amperage through
armature windings
Magnetic Motors
Conductor/Field Coil Interaction:
Magnetic fields react by moving the
conductor towards the weaker magnetic field
Armature rotates energizing the next contact
on the commutator
Magnetic Motors
Counter Electromotive Force (CEMF):
Produced by electromagnetic induction
in the windings
Tends to act against the supply voltage
Increases with motor speed
Reduces current/torque of motor
Magnetic Motors
Types of motors
Magnetic Motors
Series Wound:
Current flows through
the field windings
Then through the
armature windings
Returns to ground
Maximum torque is
developed during initial
start up
CEMF increases with
motor speed
Magnetic Motors
Parallel Wound:
Current flows in parallel
to the field windings,
positive brushes and
commutator, armature,
and grounding brushes
A low torque motor
Spins at lower speeds
CEMF does not increase
with motor speed
Magnetic Motors
Compound Wound:
Most of the field coils are in
series to the armature
One field coil is connected
to ground
Combines the best
properties of the series and
the parallel wound motors
Motor has good initial
torque and speed
Magnetic Motors
Permanent Magnet Motor:
Electromagnetic field coils
are replaced with permanent
magnets
Reduces the size and weight
of motor
Uses less current
REVIEW…..
HOW DOES A
MOTOR USE
MAGNETISM?
HOW IS
ELECTRICAL
ENERGY
CONVERTED INTO
MECHANICAL
ENERGY?
WHAT IS THE
MOVEABLE,
INTERNAL FIELD
CALLED?
WHAT IS THE
STATIONARY
OUTSIDE FIELD
CALLED?
NAME THREE WAYS
OF CONNECTING
THE 2 FIELDS
ELECTRICALLY.
REVIEW….
WHAT IS COUNTER
ELECTROMOTIVE
FORCE?
HOW DOES THE
INTERNAL FIELD
GETS IT’S POWER
AND GROUND?
HOW IS A TYPICAL
STARTER MOTOR
GROUNDED?
HOW IS A
PERMANENT
MAGNET STARTER
DIFFERENT FROM
ELECTROMAGNET
STARTER?
WHAT EFFECT DO
THE POLE SHOES
HAVE?
Elizabethtown Technical College
Basic Electricity BEXS100/101
Text: Delmar’s Standard Textbook of Electricity
Magnetic Motors