What is an Electric Vehicle?
An Electric Vehicle (EV) is one which operates on one or more motors, instead of an Internal Combustion (IC) engine. IC engine generates power by burning fuels and gases, whereas an EV uses a large traction battery pack to power up the motor. As they run on electricity, the vehicles emit no exhaust. Therefore, such a vehicle is seen as the possible replacement of the current-generation automobile. Electric vehicles are making big waves in the automobile world. These noise-free, pollution-free, and high-performance cars are expected to make their IC engine counterparts obsolete by 2025. It is so powerful that it is not limited to road and rail vehicles, it includes underwater vessels and aircraft as well.
Basic Components of Electric Vehicles –
⦁ Battery Pack: The main component of an electric car is the DC battery pack to drive the motor. Generally, a battery pack includes 16 modules constituting around 7000 Lithium-ion cells.
⦁ Charging Port: It allows the vehicle to connect to an external power supply to charge the battery pack.
⦁ Inverter: An inverter is used to convert the DC power input to AC to run the motor. It also controls the frequency, thus controlling the motor speed. Moreover, the inverter can vary the amplitude of the AC power which in turn will control the power output. Thus, the inverter acts as the “brain of the electric car”.
⦁ Electric Motor: Using power from the battery pack, this motor drives the wheels. A 3-phase induction motor is preferred over DC motor because of it’s simple and robust designing, self-starting, and higher torque. In some vehicles, the induction generator is also used to perform both the acceleration & regenerative braking.
⦁ Sensors & Controllers: With the help of sensors and power electronics controller, the speed of wheels and torque is controlled.
⦁ Thermal System: This system maintains a proper operating temperature range of the motor & other components with the help of glycol coolant.
⦁ Transmission: This transfers mechanical power from the electric motor to drive the wheels.
⦁ Regenerative Braking System: The electric vehicle has only limited energy available. Hence, to save a bit of energy, this system recovers the energy lost in braking and utilizes it to charge the batteries.
How does Electric Car Works?
⦁ DC power is produced from the battery pack and it is converted into AC with the help of an inverter.
⦁ This power is transferred to the stator of the induction motor. The 3-phase AC current produces a rotating magnetic field. This magnetic field produces current on the rotor to make it rotate.
⦁ By varying the frequency, the speed of the rotor is altered between 0-18000 rpm. This is a form of Variable Frequency Device (VFD) & Direct Torque Control (DTC).
⦁ The power output produced by the motor is then transferred to the drive wheel via a gearbox.
⦁ Output speed & torque from the motor is reduced just by changing the order of the power phase.
⦁ The gearbox & other accessories are controlled by various sensors & controllers.
⦁ When the brakes are pressed or the car is deaccelerating, the motor becomes an alternator and produces power, which is sent back to the battery.
Advantage & Disadvantage of EVs over IC engine cars -
Advantage -
⦁ Wide range of speed (0-18000 rpm) & torque compared to the IC engine (1000-5000 rpm).
⦁ Efficiency is higher (normally up to 90%) compared to the IC engine (30%). The efficiency of the IC engine is further lowered as speed is increased.
⦁ Noise-free, pollution-free, light in weight, highly safe compared to IC engine.
⦁ Less moving parts, because it’s several components required, are less. Thus, the power to weight ratio is very high in EVs.
⦁ Torque is controlled by voltage and speed is controlled by frequency. Thus, one is independent of others.
⦁ Cheaper energy cost than the ICs.
⦁ Moreover, EV provides smooth operation & stronger acceleration than ICEs.
Disadvantage –
⦁ Cost is the foremost disadvantage of EVs. The accessories are generally expensive.
⦁ Charging time is high in EV due to a lack of charging stations.
⦁ These cars are not 100% emission-free. They have to get their energy from somewhere.
Is Electric Vehicle completely safe for the environment?
The answer is, not a single man-made technology is totally safe for our environment. EVs are not out of them. According to the US Environmental Protection Agency EV can emit more CO2 than IC engines. They can produce up to 6.24 Metric Tons of toxic gasses per year. Researcher says that it can affect the environment up to 3X more than the current vehicles. Electric cars rely on electricity, which is mainly generated by fossil energy, which also generates pollution. According to a study, Emission from the tailpipes of EV will be increased from 2% in 2016 to 34% in 2030
Despite all these drawbacks, EVs are preferred over ICEs because of its comparable fewer pollution rates.
Growth of EVs in India –
India’s first electric bus was launched in Bangalore in 2014 by Ashok Leylands. Then by Tata Motors in January 2017. A Motor Vehicles Bill was passed in 2015, which established battery-powered e-rickshaws as a valid form of commercial transport in India. Indian Railways has a long history of electric locomotives, with their first use in 1925. In 2017, Govt. announced that the entire rail network in the country will be electrified by 2022. Electric vehicle sales in India up 20% in 2019-20.
Types of EVs -
Electric vehicles can be further classified into three categories as-
⦁ Battery Electric Vehicles (BEV) (e.g. Nissan LEAF, Ford Focus Electric)
⦁ Plug-in Hybrid Electric Vehicle (PHEV) (e.g. Mercedes C350e, BMW i8)
⦁ Hybrid Electric Vehicles (HEV) (e.g. Toyota Prius Hybrid, Honda Civic Hybrid)
Driving Range –
Today’s EVs generally have a shorter range than conventional cars. Extreme outside temperatures tend to reduce range because more energy must be used to heat or cool the cabin.
Future of EVs –
According to Elon Musk,” We will not stop until every car on the road is electric”. Change has begun on a small scale which will take up to 2040 to reach mass production. By 2023, the Indian Govt has set ambitious targets to run all three-wheelers on batteries. By 2025, the rule will apply to most two-wheelers.
With the drawbacks of the electric car evaded through the advent of improved technology, electric cars promise to be the cars of the future.
Sources –
Subajit Paul
EE, 2nd Year
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