Transcript DC Electric Motors

DC MOTORS
Construction & Types
Motors Everywhere!
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The fan over the stove and in the microwave oven
The dispose-all under the sink
The blender
The can opener
The washer
The electric screwdriver
The vacuum cleaner and the Dustbuster mini-vac
The electric toothbrush
The hair dryer
More Motors . . .
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The electric razor
Power windows (a motor in each window)
Power seats (up to seven motors per seat)
Fans for the heater and the radiator
Windshield wipers
Most toys that move have at least one motor (including Tickleme-Elmo for its vibrations)
Electric clocks
The garage door opener
Aquarium pumps
Your TEKBOT
In Short, EVERYTHING THAT MOVES
uses some type of motor!
Important Concepts
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How Motors Work
The Components of a DC Electric Motor
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Motor Control
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What’s inside the motor box?
The parts of the motor and what they do!
How to change directions
Concepts of Speed, Torque, Gear Ratio
Practical considerations
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Noise, slippage, limits of operation: speed, torque
DC Electric Motors
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Electric Motors or Motors convert electrical energy to
mechanical motion
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Motors are powered by a source of electricity – either AC or DC.
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DC Electric Motors use Direct Current (DC) sources of
electricity:
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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.
Motor Basics
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Motors are powered by electricity, but rely on
principles of magnetism to produce mechanical
motion.
Inside a motor we find:
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Permanent magnets,
Electro-magnets,
Or a combination of the two.
Inside a Toy Motor
(Similar to TekBot Motor)
Toy DC Motor, cont.
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End Views of Motor
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Axle
Battery Leads
Axle will turn if connect
battery leads to a 9V
battery
Reverse battery leads and
axle will turn the Opposite
direction!
The white nylon cap on the
motor can be removed to
reveal…
A View of the Brushes
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Inside the Nylon cap
are the Brushes
Brushes can be made of
various types of metal.
Their purpose is to
transfer power to the
commutator as it spins.
Inside the Motor, cont.
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The Axle is the rotating part of the
motor that holds the armature and
commutator.
This armature is comprised of 3
electromagnets. (3-Pole DC
Motor)
Each electromagnet is a set of
stacked metal plates with thin
copper wire wound around each.
The two ends of each coil wire is
terminated and wired to a contact
on the commutator.
Thus, there are 3 commutator
contacts in all.
Inside the Motor, cont.
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The final piece is the
stator, a permanent
field magnet.
It is formed by the
motor enclosure and
two curved permanent
magnets (2 Pole: 1
North, 1 South) shown.
A Two Pole DC Motor
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A Four Pole DC Motor
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Operating Principle of a DC Machine
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Armature of a DC Motor
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Armature Winding in a DC Machine
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Lap Winding of a DC Machine
• Used in high current
low voltage circuits
•Number of parallel
paths
equals number of
brushes
or poles
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Wave Winding of a DC Machine
• Used in high voltage
low current circuits
•Number of parallel
paths
always equals 2
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TYPE
S
Based on the construction the DC brushed motors are classified in to
DC seperately exited Motor
DC self exited Motor
Compound Motor.
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Separately Excited DC Machine
RA
+
Vf
Armature
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Field Coil
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Shunt Excited DC Machine
Shunt Field Coil
Armature
RA
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Series Excited DC Machine
RA
Armature
Series Field Coil
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Compound Excited DC Machine
Series Field Coil
Shunt Field Coil
Armature
RA
•If the shunt and series field aid each other it is called a cumulatively
excited machine
•If the shunt and series field oppose each other it is called a differentially
excited machine
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