however the maglev train the central japan railway company developed is quite unique and superior to the other trains running at more than 600 kilometers per hour it has achieved the status of fastest train this train usessuperconducting magnets which is why it is called sc maglive once charged with an exciting current the superconducting magnets of this train produce a circulating dc current and strong magnetic field forever with zero loss let's understand more about the successfully tested train technology which is projected to overtake other magnetic levitation technologies by the year 2027 the same technology is poised to connect new york city to washington dc in just one by 2030.we have to achieve the following three objectives one propel two levitate and three guidance however before we get into the details of how the sc maglev train achieves these objectives study about the heart of this train the superconducting magnets levitating trains require enormously powerful electromagnets the stronger the magnets the more lift force and propelling force they have resulting in higher train speed a normal electromagnet.
is not able to increase the current
value beyond a certain limit
due to the heating issue
in the superconducting electromagnets
the temperature of the conductor
is lowered below a critical limit after
this
the material suddenly produces a huge
amount of current flow
with zero resistance that result
is exactly what we want the interesting
thing
is that you only need to charge the
superconducting coil
once using an exciting current in order
for the short-circuited coils to produce
a circulating
dc current forever with no energy loss
the current circulated by the
superconducting coils is huge
700 kilo amperes almost 10 000 times the
current value
of the conventional household copper
gauge wires
the superconducting electromagnets are
obviously the most powerful
and efficient electromagnets
the challenge is to keep the coils in a
superconducting stage
for this purpose an onboard liquid
helium refrigeration system is used
the superconductor in the sc maglev
train is a niobium titanium alloy
which has a critical temperature of 9.2
kelvin
to keep the alloy temperature below this
limit liquid helium
at a temperature of 4.5 kelvin is
circulated around it
after passing over the conductor the
liquid helium evaporates
to bring it back to the initial stage a
helium compressor and refrigeration unit
is used
the refrigeration unit works on the
principle of gilford mcmahon
refrigeration cycle
still the cryogenic department's
engineering task is not finished yet
the superconductor can absorb heat from
outside in the form of radiation
to prevent this absorption from
occurring a radiation shield is added
around it
however during the trains operation any
current formation
and heating issues can happen in this
shield
to neutralize this heating the radiation
shield also needs cooling
which is achieved by supplying liquid
nitrogen to the unit
to prevent convective heat transfer a
vacuum
is maintained inside the radiation
shield
four such superconductors with opposing
current polarity
are arranged in a unit although in an sc
maglev
the electromagnets work without any
power supply the cryogenics department
demands a good amount of power
such many units are attached along the
length of the train
on both sides
as mentioned the first task is
propulsion
propelling the train forward is an easy
task for this purpose
we use a series of normal electromagnets
they are called propelling coils
the propelling coils are powered in an
alternative manner as shown
and are placed inside a guideway
next we need to find out the force the
propelling coils are producing on the
train's superconducting magnets
please note that to understand the
direction of force one magnet produces
on the other
you just have to consider the nearest
poles
in this way let's analyze the force
acting on the superconducting coils
due to the propelling coils
if you take the result of all these
forces the net force will be in the
forward direction
so the train moves forward as soon as
the train reaches the next mean position
switch the electromagnets to the
alternate polarity so that the net force
is again
in the forward direction just by
controlling the frequency of this
switching
you can control the train speed now
let's get to the most interesting part
of this technology
the levitation of the sc maglev trains
you may be surprised to learn that the
sc maglev train's levitation
is achieved with the help of these
simple figure eight shaped coils
which are not even powered
many such eight figure shaped coils are
arranged in the guideway
to understand the levitation technology
we should first learn something about
the nature of a pair of superconducting
magnets
the resultant magnetic field produced by
this pair of
sc magnets is very similar to a long
permanent magnet
so for simplification of the analysis
let's replace this pair with a long bar
magnet
if a bar magnet moves parallel to these
figure eight-shaped coils
can you predict what will happen
the varying magnet flux will induce emf
on both the loops according to faraday's
law
are these emfs in the same direction
please note that this is a twisted coil
only when we unwind it will we
understand the right direction
it is clear the induced emfs are
opposite in direction
which means net emf induced on this coil
due to the bar magnet movement is zero
and no current will flow through the
loop
in short a bar magnet moving through the
center of the loop
won't have any effect on the loop
now consider the same case but this time
the magnet is slightly offset to the
loop
as shown here the bottom loop faces
magnetic flux of higher strength
which means the emf induced on the
bottom loop will be higher than on the
top
this higher strength also means that a
net current will flow
through the loop this current flow
produces a south pole
on the top loop and a north pole on the
bottom loop
if you analyze the force interaction
between the magnetic poles
it's clear that a resultant upward force
is imposed on the superconducting magnet
if this force is more than the
gravitational pull
the magnet will move up yes movement of
a superconducting magnet
parallel and offset to a figure eight
shaped coil
produces levitation
as the magnet moves up the difference
between emf values
and the current flow in the loop reduces
which means the force on the loop also
reduces
finally when the upward force becomes
equal to the gravitational pull
the magnet balances or the train has
achieved levitation
japanese engineers achieved a levitation
of 3.9 inches
using this technology
clearly the higher the train speed the
greater the levitation force
which means that when the train is at
rest it cannot levitate
this is why the sc maglev train uses
normal tires for starting
and low speed operation when the train
achieves a critical speed
the tires retract as the electromagnetic
force is strong enough to levitate the
train
next comes the question of train
guidance
guidance means the train should always
be centered it should move without
hitting the sidewalls
in other words it should achieve lateral
stability
japanese engineers achieve this
stability quite easily
by interconnecting the figure
eight-shaped coils we saw earlier
as shown if the train is in the center
the induced emfs on the right and left
coils will be equal
and no current will flow through the
interconnecting coils
however suppose the train has moved
slightly towards the right
this shift will cause an emf difference
between the right and left coils
resulting in the interconnecting coils
having a current flow
the current flow through the
interconnecting coils will drastically
affect the current flow in both the
bottom loops
and thus the pole strength of each loop
let's analyze the forces acting on the
train now
you can see that the vertical components
of the forces remain the same
but a net horizontal component manifests
towards the left
which forces the train to move back to
the center
as the train nears the center the
currents in the interconnecting loops
decrease and finally the horizontal
component of the force
disappears what an easy and brilliant
mechanism to stabilize the train right
from the discussion so far you might
understand that the cryogenic system of
the train
and the other electrical appliances of
the train require a huge amount of
electrical power
how do you transfer electrical power to
such a high-speed train
the central japan railway used a
technique called
inductive power collection for this
purpose
here using the principle of
electromagnetic induction
electric power is transferred from the
ground coils
to the power collection coil in the
train without any material contact
the strong magnetic field the
superconducting magnets produce
can have health hazards on passengers to
avoid this unwanted effect
magnetic shields are used on the rolling
stock and passenger embarkation facility
thus keeping the strength of the
magnetic field below icn
irp guidelines sc maglev train test
rides began
in 1997 on the yamanashi maglev test
line
the test rides were quite successful and
continued for 10 consecutive years
without missing
a single day a world record speed of 603
kilometers per hour
was achieved during this time these
highly positive results encouraged the
japanese authorities
and they granted permission to conduct
commercial sc maglev operations
between tokyo and nagoya by the year
2027
with more sc maglev trains to follow
the sc maglev train technology revolves
around the physics of superconductivity
which is a crazy and amazing phenomenon
to understand what superconductivity is
in a logical way
please check out this interesting video
from arvin ash
also please don't forget to be part of
our team
thank you
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