Electric cars are making big waves in the automobile world.
These noise-free, pollution-free and high-performance vehicles
are expected to make their IC engine counterparts obsolete by 2025.
This video will unveil the hidden technologies behind the Tesla model S,
which recently became the world's fastest accelerating car.
We will see how electric cars have achieved superior performance
by analyzing the technology behind the induction motor,
inverter,
lithium-ion battery power source,
and, above all, the synchronized vehicle mechanism,
in a logical step-by-step manner.
The powerhouse of the Tesla car is an invention
made by the great scientist Nikola Tesla around 100 years back:
the induction motor.
The induction motor has two main parts:
the stator and the rotor.
You can see the construction details of the motor here.
The rotor is simply a collection of conducting bars short-circuited by end rings.
A three-phase AC power input is given to the stator.
The three-phase alternating current in the coils produces a rotating magnetic field.
The Tesla motor produces a four-pole magnetic field.
This rotating magnetic field that induces current on the rotor bars to make it turn.
In an induction motor, the rotor always lags behind the RMF.
An induction motor has neither brushes nor a permanent magnet.
At the same time it is robust and powerful.
The beauty of an induction motor is that
its speed depends on the frequency of the AC power supply.
So just by varying the frequency of the power supply,
we will be able to alter the drive wheel speed.
This simple fact makes electric car speed control easy and reliable.
The motor supply is from a variable frequency drive,
which in turn controls motor speed.
The motor speed can range from 0 to 18,000 rpm.
This is the most sizable advantage electric cars have
when compared to internal combustion cars.
An internal combustion engine produces usable torque
and power output only within limited speed range.
Therefore,
directly connecting the engine rotation to the drive wheel is not a clever idea.
A transmission must be introduced to vary the drive wheel speed.
On the other hand, an induction motor will work efficiently in any speed range.
Thus, no speed varying transmission is needed for an electric car.
Moreover, an IC engine does not produce direct rotational motion.
The linear motion of the piston has to be converted to rotational motion.
This causes major problems for mechanical balancing.
Not only is the internal combustion engine not self-started like an induction motor.
Further, the power output of an IC engine is always uneven.
Many accessories are needed to solve these issues.
On the other hand, you will have direct rotational motion
and uniform power output with an induction motor.
Many components in the IC engine can be avoided here.
As a result of these factors,
a great response rate and higher power to weight ratio
comes naturally to an induction motor resulting in superior vehicle performance.
But from where does the motor receive power?
It's from a battery pack.
The battery produces DC power.
So before supply get to a motor it has to be converted to AC.
An inverter is used for this purpose.
This power electronic device also controls the AC power frequency,
thus controlling the motor speed.
Moreover, the inverter can even vary the amplitude of the AC power
which in turn will control the motor power output.
Thus, the inverter acts as the brain of the electric car.
Now, let's turn our focus to the battery pack.
You will be amazed to find
that they are just a collection of common lithium-ion cells
similar to those used in your daily life.
The cells are connected in a combination of series and parallel
to produce the power required to run your electric car.
Glycol coolant is passed through metallic inner tubes
through the gap between the cells.
This is one principal innovation of Tesla.
By using many small cells instead of a few big cells
effective cooling is guaranteed.
This minimizes thermal hot spots and even temperature distribution is achieved
leading to higher battery pack life.
The cells are arranged as detachable modules.
There are 16 such modules in the battery pack constituting around 7,000 cells.
The heated Glycol is cooled down by passing through a radiator,
which is fitted at the front of the vehicle.
Moreover, you can see how such a low height battery pack,
when fitted close to the ground level, will lower the vehicle center of gravity.
The lower of gravity improves the stability of the car considerably.
The large battery pack is also spread across the floor
offering structural rigidity against side collisions.
Now let's get back to Tesla's drive-train.
The power produced by the motor is transferred to the drive wheels via a gearbox.
As previously discussed, Tesla Model S uses a simple single speed transmission
because the motor is efficient in a wide range of operating conditions.
You can see that output speed from the motor is reduced in two steps.
Even achieving the reverse gear is quite easy in an electric car.
Just change the order of the power phase for this.
The only purpose of electric car transmission
is speed reduction and associated torque multiplication.
The second component in the gearbox is a differential.
The reduced speed drive is passed to it.
You can see this is a simple open differential.
However, open differentials, have a problem of traction control.
But, why does such an advanced car use an open differential
rather than a limited slip differential?
The answer is that the open differential is more rugged and can carry more torque.
The traction control problem that occurs in an open differential
can effectively be overcome with help of two methods:
selective braking
and cutting the power supply.
In an internal combustion engine,
this power supply cut by cutting the fuel is not so responsive.
In an induction motor, however, the power supply cut is quite responsive
and an effective means for obtaining traction control.
In the Tesla,
this can all be accomplished using a state-of-the-art algorithm
with help from Sensors and controllers.
In short, Tesla Motors has replaced a complex mechanical hardware system
with smart responsive software.
Did you know an electric car could be driven efficiently
with the help of just one pedal?
This is due to its powerful regenerative braking system.
That means saving the huge kinetic energy of the car
in the form of electricity without wasting it as heat.
In an electric car, as soon as you release the accelerator pedal,
the regenerative braking comes into action.
The interesting thing is that, during the regenerative braking
the same induction motor acts as a generator.
Here the wheels drive the rotor of the induction motor.
We know in an induction motor the rotor speed is less than the RMF speed.
To convert the motor to a generator,
you just have to make sure that the rotor speed is greater than the RMF speed.
The inverter plays a crucial role here in adjusting the input power frequency
and keeping the RMF speed below the rotor speed.
This will generate electricity in the stator coils,
which is way higher than the supplied electricity.
The generated electricity can then be stored
in the battery pack after the conversion.
An opposing electromagnetic force acts on the rotor during this process,
so the drive wheels and the car will slow down.
This way vehicle speed can be accurately controlled
during the drive using a single pedal.
The brake pedal can be applied for a complete stop.
As you might already be aware,
electric cars are much safer than internal combustion cars.
The cost of maintaining and driving an electric car
is much lower than that of an IC engine car.
With the drawbacks of the electric car evaded
through the advent of improved technology,
electric cars promise to be the cars of the future.
We thank Mr. Jehu Garcia,
an electric car expert and YouTuber for his technical support for this video.
Your support at patreon.com is highly appreciated.
It enables us to make additional free educational videos for you.
Thank you.