They are used to
change voltage by
stepping up theprimary voltage on the
secondary side
or
stepping down the voltage. They are also used to match impedance and as
isolating devices that isolate the ground.
A.C. is required to operate transformers because the
voltage induction
that occurs between the primary and secondary requires a rapidly
expanding
and collapsing electromagnetic field that only alternating current provides.
Because electrical power distributed as
high voltage has a reduced
current, smaller cable sizes can be used.
The cost effectiveness of
smaller cables is the reason for high voltage distribution but it must
be stepped back down for consumer safety.
Tesla
developed AC polyphase distribution systems and devices and kicked
off the
"2nd Industrial Revolution"
AC can be transformed to dangerous but far traveling voltages and
then stepped back down to relatively safe voltages for the consumer Tesla CoilTesla Video ShrineTesla RoadsterBBC Tesla Documentary
Recall the right hand rule :
grab the conductor with right hand
thumb points in direction of current flow
fingers point towards the North pole of the electromagnetic field
remember in AC a reversal is
happening 60 times as second
When a magnetic field cuts through a conductor a
voltage is induced
in the conductor.
If the conductor forms a closed circuit,
current will and create a magnetic field that opposes the field that
induces the voltage
Lenz;s L
the alternating magnetic field of the
primary field induces a voltage in the secondary
The
lower coil (primary) induces a voltage in
the upper coil (secondary) energizing
the lamp
The batteries of an
electric vehicle
are energized by an "inductive
pluggin puck" the puck is the primary
Your electric toothbrush......
or the hypodermal battery of a human pacemaker can be
recharged by inductive means
what type of transformer is this a
step up or step down transformer?
if 100 volts AC are applied at the
primary what is the voltage at the secondary of this transformer
if 10 amp are input what current
flows from the secondary?
if 250 w are input how much power is
output?
Step Up or Step
Down ?
the iron core is permeable to electromagnetic fields so it is
concentrates
the changing field causes the iron atoms to flip flop generating
heat thus wasting some energy
Multi cylinder internal combustion
engines use a
coil and distributor to ignite fuel in the combustion
chambers
Here, although no voltage change would
occur, the load is electrically isolated from the source.
Hence the term isolating
transformer
Remember that the power going into a
transformer is the same as the power coming out
Pin = Pout
StepDownVsdown
Isup
StepUp
Vsup
Isdown
Center tapped transformer
Can be multi tapped to provide multiple voltages
(as in single phase 120/240v systems)
Or to trim final
output
Step down
pole transformer stepping down
8000V to single phase
120/240V
- note the neutral supported triplex cable - lines 1 + 2 twist around the bare
neutral support cable