(SEM VIII) THEORY EXAMINATION 2022-23 ELECTRIC VEHICLES

ELECTRIC VEHICLES (KOE-090)

B.Tech Semester VIII – Theory Answers

SECTION A

(a) Importance of electric vehicles

Electric vehicles play a crucial role in reducing environmental pollution and dependence on fossil fuels. They operate with zero tailpipe emissions, which helps in improving air quality and reducing greenhouse gas emissions. Electric vehicles also contribute to energy efficiency, lower operating costs, and reduced noise pollution. With the increasing demand for sustainable transportation, EVs support national energy security and align with global climate goals.

(b) Challenges involved in using electric vehicles

The use of electric vehicles faces several challenges such as limited driving range, long charging time, high initial cost, and inadequate charging infrastructure. Battery degradation, availability of raw materials, and disposal of batteries are additional concerns. These challenges affect consumer acceptance and large-scale adoption of electric vehicles.

(c) Electromechanical batteries

Electromechanical batteries are energy storage systems that store electrical energy in mechanical form and convert it back into electrical energy when required. Examples include flywheel energy storage systems. These batteries offer high power density, long cycle life, and fast response, making them suitable for certain EV applications.

(d) Applications of fuel cells

Fuel cells are used in electric vehicles for clean energy generation. They are also applied in stationary power generation, backup power systems, aerospace applications, and portable power devices. Fuel cells are preferred due to their high efficiency and low environmental impact.

(e) Methods for starting an induction motor

Induction motors can be started using various methods such as direct-on-line starting, star-delta starting, autotransformer starting, and rotor resistance starting. These methods help limit starting current and reduce mechanical stress on the motor and power system.

(f) Use of permanent magnet motor

Permanent magnet motors are widely used in electric vehicles due to their high efficiency, high power density, and compact size. They are commonly used in traction applications, electric power steering, and auxiliary systems in EVs.

(g) Fleming’s left-hand rule

Fleming’s left-hand rule is used to determine the direction of force acting on a current-carrying conductor placed in a magnetic field. According to this rule, if the thumb, forefinger, and middle finger of the left hand are mutually perpendicular, then the forefinger represents the magnetic field, the middle finger indicates current, and the thumb shows the direction of motion.

(h) Hybrid vehicles

Hybrid vehicles use a combination of an internal combustion engine and an electric motor for propulsion. This combination improves fuel efficiency, reduces emissions, and enhances performance. Hybrid vehicles can operate in electric mode, engine mode, or a combination of both.

(i) Components removed from IC engine vehicle when converting to EV

When converting an IC engine vehicle into an electric vehicle, components such as the engine, fuel tank, exhaust system, radiator, gearbox (in some cases), and fuel injection system are removed. These components are replaced by electric motors, batteries, and power electronics.

(j) Function of gearbox in a vehicle

The gearbox transmits power from the motor or engine to the wheels while adjusting torque and speed according to driving conditions. It allows smooth acceleration, efficient power transfer, and optimal vehicle performance.

SECTION B

2(a) Components of electric vehicles

Electric vehicles consist of major components such as battery pack, electric motor, power electronics controller, DC-DC converter, onboard charger, and drivetrain. The battery pack stores electrical energy, while the electric motor converts electrical energy into mechanical motion. Power electronics control the flow of energy, ensuring efficient operation. The drivetrain transfers power to the wheels, and auxiliary systems support vehicle operation.

2(b) Lead-acid battery schematic, structure, advantages and limitations

A lead-acid battery consists of lead dioxide as the positive plate, sponge lead as the negative plate, and sulfuric acid as the electrolyte. During charging and discharging, chemical reactions convert electrical energy to chemical energy and vice versa. Lead-acid batteries are inexpensive, reliable, and easily recyclable. However, they have low energy density, shorter lifespan, and higher weight compared to modern batteries.

2(c) Compound wound DC motor

A compound wound DC motor has both series and shunt field windings. The shunt field provides constant speed characteristics, while the series field improves starting torque. This motor combines the advantages of both types. Voltage and current equations describe the relationship between armature voltage, current, resistance, and induced emf, making it suitable for EV traction applications.

2(d) Design considerations and charging methods of EV charging system

Design considerations of an EV charging system include charging speed, safety, compatibility, efficiency, and grid impact. Charging methods include slow charging, fast charging, and rapid DC charging. Proper design ensures battery longevity, user convenience, and system reliability.

2(e) Identification of EV demand and impact of EV charging on power grid

EV demand is identified based on factors such as fuel prices, environmental awareness, government policies, and infrastructure availability. EV charging impacts the power grid by increasing load demand, affecting peak load conditions, and requiring grid upgrades. Smart charging and load management help mitigate these effects.

SECTION C

3(a) Comparison between petrol vehicle and electric vehicle

Petrol vehicles rely on internal combustion engines and fossil fuels, leading to higher emissions and fuel costs. Electric vehicles use electric motors and batteries, resulting in zero tailpipe emissions and lower operating costs. While petrol vehicles offer longer range and faster refueling, EVs provide higher efficiency, reduced maintenance, and environmental benefits.

3(b) Historical development of automobiles and evolution of electric vehicles

The automobile industry began in the late 19th century with steam and electric vehicles. In the early 1900s, electric vehicles were popular due to their simplicity and quiet operation. However, IC engine vehicles dominated due to fuel availability and technological advancements. In recent decades, interest in EVs has resurged due to environmental concerns, battery improvements, and government support, leading to widespread adoption today.