Download Topic 6 - Generators and Motors

Topic 6 - Generators and Motors
A device that converts mechanical energy
(energy of motion – windmills, turbines,
nuclear power, falling water, or tides) into
electrical energy is called an electric generator.
The operation of a generator depends on the
relationship between electricity and
magnetism.
Electricity to Magnetism
• Oersted found that current creates a magnetic
field around a wire.
• The amount of needle deflection depended on
how much electric current was flowing in the
wire.
• When the current was reversed, the needle
moved in the opposite direction.
• Demo
Electromagnets
• When a soft iron core is inserted into a coil of
wire and a current is passed through the wire,
a very strong “temporary” magnet is
produced, called an electromagnet
• When the current is shut off, the
electromagnet loses its power.
• The strength of an electromagnet is affected
by the …
A. type and size of core
B. strength of current
C. number of coils
http://www.youtube.com/watch?v=emlzh9XXW
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Magnetism to Electricity
• Faraday discovered electromagnetic induction in
1831. He demonstrated that moving a conducting
wire back and forth through a magnetic field
generated a current.
• Faraday created the first electricity-producing
generator, which could generate electrical
current.
• He also found that moving the magnet worked as
well.
• Demo
What’s in a Generator?
• An AC generator – the most common type –
has a coil of wire rotating inside a stationary
field magnet.
• The electricity produced by this type of
generator is called alternating current
because it changes direction (in N. America it
changes direction 120 times per second)
DC Generators
• A DC generator is much the same as a DC
motor, and is often called a dynamo.
• The DC generator’s pulsating electricity is
produced in one direction - referred to as
direct current
The St. Louis Motor.
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Label the parts of the St. Louis Motor.
Armature
Brushes
Split Ring Commutator
Permanent Magnet
Electrodes
How the St. Louis Works!!
• Electrodes are connected to the power source
• Brushes connect the electrodes to the split
ring commutator
• Split ring commutator allows an interruption
in the current and reverses the poles of the
electromagnet.
• Electrodes are connected to the power source
• Brushes connect the electrodes to the split
ring commutator
• Split ring commutator allows an interruption
in the current and reverses the poles of the
electromagnet.
Electric Motors: Electric to Mechanical
Energy
• Generators and Motors are built exactly the
same. They work in reverse of one another.
• Generators move or use mechanical energy to
produce an electric current.
• Motors use the electric current to produce
movement (Mechanical Energy)