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POWER
Engines
– During the industrial revolution, steam engines were used to run
machines in a factory, to move trains and boats
– In a factory, the flywheel of the steam engine was connected by
canvas belts to a shaft that ran the length of the factory, high
overhead
 Reaction Engines
– Newton’s third law explains why reaction engines work --- jet &
rocket engines
– In a jet engine, the burnt mixture of air and fuel
– Rocket engines carry their own oxygen supply
 Nuclear Reactors
– Large amounts of energy are released when large atomic nuclei
are split
– The reactor can move a ship and fulfill its electricity needs as well
Engines
 Electrical Motors
– They change electrical
energy into rotary motion
– Small motors deliver less
than one horsepower --fractional horse power
motors
– They must carry their power
source with them
Transmission
– They are used to carry force and motion from the engine of a
power system to the object to be moved (the load)
– Transmissions can be mechanical, hydraulic or electrical
 Mechanical Power Transmission
– Mechanical transmissions (sometimes called mechanisms) are
very simple parts
– Gears, pulleys, cams, levers, and linkages
 Hydraulic Power Transmission
– They transmit force through a tubing that carries the fluid
– Pressure = force on a liquid/area
– Pistons of different sizes can be used to obtain larger or smaller
forces
Transmission
 Electrical Power Transmission
– Alternating current, or ac is produced by generators at power
plants
– Electricity changed to heat by the resistance in the wires is lost
– Transformers are used to change the voltage of the current
– Transmission lines from several generating stations are often
joined in a grid
– Superconductivity holds promise for saving the loss of electricity in
terms of heat
– Superconductivity is possible in materials that were cooled nearly
to absolute zero --- a temperature at which molecules stop moving
--- about –459 F
Continuous/Intermittent Power
Systems
– Continuous power systems are nearly always available, e.g. an
internal combustion engine
– Intermittent power systems sometimes store energy
– Solar cells charge a battery when the sun shines
– The battery in a car is recharged by a generator called a alternator