WEBVTT

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Electric cars are making big waves
in the automobile world.

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These noise-free, pollution-free
and high-performance vehicles

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are expected to make their IC engine
counterparts obsolete by 2025.

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This video will unveil the hidden 
technologies behind the Tesla model S,

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which recently became the world's
fastest accelerating car.

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We will see how electric cars have
achieved superior performance

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by analyzing the technology 
behind the induction motor,

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inverter,

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lithium-ion battery power source,

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and, above all, the synchronized
vehicle mechanism,

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in a logical step-by-step manner.

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The powerhouse of the Tesla
car is an invention

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made by the great scientist Nikola Tesla
around 100 years back:

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the induction motor.

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The induction motor has two main parts:

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the stator and the rotor.

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You can see the construction
details of the motor here.

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The rotor is simply a collection of conducting
bars short-circuited by end rings.

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A three-phase AC power input
is given to the stator.

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The three-phase alternating current in
the coils produces a rotating magnetic field.

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The Tesla motor produces 
a four-pole magnetic field.

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This rotating magnetic field that induces
current on the rotor bars to make it turn.

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In an induction motor, 
the rotor always lags behind the RMF.

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An induction motor has neither 
brushes nor a permanent magnet.

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At the same time it is robust and powerful.

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The beauty of an induction motor is that

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its speed depends on 
the frequency of the AC power supply.

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So just by varying the frequency
of the power supply,

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we will be able to alter 
the drive wheel speed.

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This simple fact makes electric car 
speed control easy and reliable.

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The motor supply is from 
a variable frequency drive,

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which in turn controls motor speed.

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The motor speed can range
from 0 to 18,000 rpm.

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This is the most sizable
advantage electric cars have

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when compared to internal combustion cars.

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An internal combustion engine
produces usable torque

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and power output only 
within limited speed range.

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Therefore,

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directly connecting the engine rotation
to the drive wheel is not a clever idea.

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A transmission must be introduced
to vary the drive wheel speed.

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On the other hand, an induction motor
will work efficiently in any speed range.

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Thus, no speed varying transmission
is needed for an electric car.

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Moreover, an IC engine does not
produce direct rotational motion.

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The linear motion of the piston has 
to be converted to rotational motion.

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This causes major problems 
for mechanical balancing.

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Not only is the internal combustion engine
not self-started like an induction motor.

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Further, the power output of
an IC engine is always uneven.

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Many accessories are needed
to solve these issues.

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On the other hand, you will
have direct rotational motion

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and uniform power output 
with an induction motor.

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Many components in the IC engine
can be avoided here.

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As a result of these factors,

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a great response rate and
higher power to weight ratio

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comes naturally to an induction motor
resulting in superior vehicle performance.

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But from where does 
the motor receive power?

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It's from a battery pack.

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The battery produces DC power.

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So before supply get to a motor 
it has to be converted to AC.

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An inverter is used for this purpose.

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This power electronic device also
controls the AC power frequency,

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thus controlling the motor speed.

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Moreover, the inverter can even
vary the amplitude of the AC power

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which in turn will control 
the motor power output.

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Thus, the inverter acts as 
the brain of the electric car.

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Now, let's turn our focus 
to the battery pack.

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You will be amazed to find

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that they are just a collection
of common lithium-ion cells

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similar to those used in your daily life.

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The cells are connected in a combination
of series and parallel

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to produce the power required 
to run your electric car.

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Glycol coolant is passed 
through metallic inner tubes

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through the gap between the cells.

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This is one principal innovation of Tesla.

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By using many small cells
instead of a few big cells

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effective cooling is guaranteed.

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This minimizes thermal hot spots and
even temperature distribution is achieved

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leading to higher battery pack life.

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The cells are arranged 
as detachable modules.

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There are 16 such modules in the battery
pack constituting around 7,000 cells.

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The heated Glycol is cooled down
by passing through a radiator,

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which is fitted at
the front of the vehicle.

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Moreover, you can see how
such a low height battery pack,

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when fitted close to the ground level,
will lower the vehicle center of gravity.

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The lower of gravity improves
the stability of the car considerably.

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The large battery pack is
also spread across the floor

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offering structural rigidity 
against side collisions.

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Now let's get back to Tesla's drive-train.

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The power produced by the motor is
transferred to the drive wheels via a gearbox.

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As previously discussed, Tesla Model S
uses a simple single speed transmission

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because the motor is efficient in 
a wide range of operating conditions.

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You can see that output speed from 
the motor is reduced in two steps.

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Even achieving the reverse gear
is quite easy in an electric car.

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Just change the order of
the power phase for this.

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The only purpose of electric
car transmission

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is speed reduction and
associated torque multiplication.

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The second component in 
the gearbox is a differential.

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The reduced speed drive is passed to it.

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You can see this is 
a simple open differential.

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However, open differentials, 
have a problem of traction control.

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But, why does such an advanced
car use an open differential

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rather than a limited slip differential?

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The answer is that the open differential
is more rugged and can carry more torque.

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The traction control problem that
occurs in an open differential

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can effectively be overcome 
with help of two methods:

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selective braking

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and cutting the power supply.

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In an internal combustion engine,

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this power supply cut by cutting
the fuel is not so responsive.

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In an induction motor, however,
the power supply cut is quite responsive

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and an effective means for
obtaining traction control.

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In the Tesla,

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this can all be accomplished using
a state-of-the-art algorithm

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with help from Sensors and controllers.

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In short, Tesla Motors has replaced 
a complex mechanical hardware system

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with smart responsive software.

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Did you know an electric car
could be driven efficiently

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with the help of just one pedal?

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This is due to its powerful 
regenerative braking system.

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That means saving the huge
kinetic energy of the car

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in the form of electricity 
without wasting it as heat.

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In an electric car, as soon as
you release the accelerator pedal,

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the regenerative braking 
comes into action.

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The interesting thing is that,
during the regenerative braking

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the same induction motor 
acts as a generator.

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Here the wheels drive the rotor
of the induction motor.

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We know in an induction motor 
the rotor speed is less than the RMF speed.

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To convert the motor to a generator,

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you just have to make sure that the rotor
speed is greater than the RMF speed.

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The inverter plays a crucial role here
in adjusting the input power frequency

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and keeping the RMF speed
below the rotor speed.

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This will generate electricity
in the stator coils,

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which is way higher than 
the supplied electricity.

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The generated electricity 
can then be stored

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in the battery pack after the conversion.

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An opposing electromagnetic force acts
on the rotor during this process,

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so the drive wheels and 
the car will slow down.

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This way vehicle speed can 
be accurately controlled

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during the drive using a single pedal.

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The brake pedal can be applied 
for a complete stop.

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As you might already be aware,

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electric cars are much safer 
than internal combustion cars.

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The cost of maintaining and
driving an electric car

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is much lower than that 
of an IC engine car.

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With the drawbacks of the electric car evaded

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through the advent of improved technology,

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electric cars promise to 
be the cars of the future.

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We thank Mr. Jehu Garcia,

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an electric car expert and YouTuber
for his technical support for this video.

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Your support at patreon.com 
is highly appreciated.

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It enables us to make additional 
free educational videos for you.

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Thank you.