(SEM VIII) THEORY EXAMINATION 2023-24 ELECTRIC VEHICLES

SECTION A

(Attempt all | 2 × 10 = 20 Marks)

a. Define rolling resistance.
Rolling resistance is the force that opposes the motion of a vehicle due to deformation of tyres and road surface during rolling.

b. Write the advantage of EV.
Electric vehicles have zero tailpipe emissions, high energy efficiency, low operating cost, and reduced noise pollution.

c. Write the classification of electric vehicle.
Electric vehicles are classified as Battery Electric Vehicle (BEV), Hybrid Electric Vehicle (HEV), Plug-in Hybrid Electric Vehicle (PHEV), and Fuel Cell Electric Vehicle (FCEV).

d. What is SRM in electric vehicle?
SRM stands for Switched Reluctance Motor. It is an electric motor that operates based on reluctance torque and is known for simple construction and high reliability.

e. What is a 2nd life lithium battery?
A second-life lithium battery is a used EV battery that is repurposed for stationary energy storage after its automotive performance degrades.

f. What do you mean by Smart battery pack?
A smart battery pack includes sensors, BMS, communication interfaces, and protection circuits to monitor health, temperature, voltage, and current.

g. Mention the charging methods of battery.
Charging methods include AC charging, DC fast charging, wireless charging, and regenerative charging.

h. What is onboard charger?
An onboard charger is a power electronic unit inside the EV that converts AC grid power into DC to charge the battery.

i. What is the role of aggregator in V2G?
An aggregator coordinates multiple EVs to manage power exchange with the grid in Vehicle-to-Grid (V2G) systems.

j. What is scheduling energy?
Scheduling energy refers to planned allocation and timing of energy usage or supply to optimize grid stability and cost.

SECTION B

(Attempt any THREE | 10 × 3 = 30 Marks)

2(a) Evaluation of Electric Vehicles

Evaluation of EVs includes performance, efficiency, range, cost, emissions, and lifecycle assessment. Key parameters are acceleration, top speed, energy consumption per km, battery efficiency, charging time, maintenance cost, and environmental impact. EVs are evaluated using driving cycles, simulation tools, and real-world testing to ensure reliability and safety.

2(b) Axial Flux Motor and its Working Principle

An axial flux motor has magnetic flux flowing parallel to the axis of rotation. It consists of disc-shaped rotors and stators. When current flows through stator windings, a magnetic field is created that interacts with the rotor, producing torque. These motors offer high power density and compact size, making them suitable for EVs.

2(c) Factors affecting the performance of EV batteries

Battery performance depends on temperature, charge-discharge rate, depth of discharge, battery chemistry, aging, internal resistance, and charging method. Poor thermal management and overcharging reduce battery life and efficiency.

2(d) Modes of charging batteries and comparison

Battery charging modes include slow AC charging, fast DC charging, and ultra-fast charging.

AC charging: Low cost, slow, suitable for home charging

DC fast charging: High power, quick charging, higher infrastructure cost

Wireless charging: Convenient but less efficient

2(e) Energy Management System (EMS) in EHV

EMS controls power flow between battery, motor, regenerative braking, and auxiliary systems. Issues include battery aging, thermal constraints, efficiency optimization, and real-time decision making under varying driving conditions.

SECTION C

3(a) Comparison of IC Engine Vehicle and Electric Vehicle

IC engine vehicles use fossil fuels, produce emissions, and have lower efficiency. EVs use electric motors, offer higher efficiency, zero tailpipe emissions, and lower maintenance cost. However, EVs face challenges like charging infrastructure and battery cost.

3(b) General layout of an EV and transmission characteristics

An EV consists of battery pack, power electronics, electric motor, transmission, controller, and wheels. EVs usually use single-speed transmission due to wide torque-speed characteristics of electric motors.

4(a) Sizing of power electronics in hybrid vehicle

Power electronics sizing depends on motor rating, battery voltage, current requirements, efficiency, thermal limits, and operating conditions. Proper sizing ensures reliability and performance.

4(b) Classification of EV motors & torque-speed characteristics of SRM

EV motors include DC motors, BLDC motors, PMSM, induction motors, and SRM.
SRM torque-speed characteristics show high torque at low speed and wide constant-power region, suitable for EV traction.

5(a) Lithium-based batteries

Lithium-ion batteries use lithium compounds as electrodes. They offer high energy density, long cycle life, low self-discharge, and are widely used in EVs.

5(b) Battery Management System (BMS)

BMS monitors battery voltage, current, temperature, SOC, and SOH. It ensures safe operation, balances cells, protects against overcharge/over-discharge, and improves battery life.

6(a) Charging algorithms and discharging methods

Charging algorithms include Constant Current (CC), Constant Voltage (CV), and CC-CV method. Discharging methods ensure controlled power delivery while maintaining battery safety.

6(b) OCPP protocol and its working

OCPP (Open Charge Point Protocol) enables communication between EV chargers and central management systems. It supports authentication, monitoring, billing, and remote control of charging stations.

7(a) Application of AI in EVs

AI is used in battery health prediction, autonomous driving, energy management, predictive maintenance, and charging optimization. In future EVs, AI will enhance efficiency, safety, and user experience.

7(b) Need of energy management system in HEV & EV

EMS is essential in HEVs to manage multiple energy sources. EVs also require EMS for battery optimization, thermal control, and regenerative braking, though complexity is lower than HEVs.