How Does an Electric Vehicle Work?
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 Post will unveil the hidden technologies behind the Tesla Model S which recently became the world’s the 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 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 induces a 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 Zero 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 the limited speed range, Therefore, directly connecting the engine rotation to the drive wheel is not a clever idea. 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, but the power output of an IC engine is also 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?
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 drivetrain
The power produced by the motor is transferred to the drive wheels via a gearbox As previously discussed, the 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 A problem that occurs in an open differential can effectively be overcome with the 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
Thumbnail Image Source: Autojournalism.com
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