(SEM VIII) THEORY EXAMINATION 2021-22 ELECTRIC VEHICLES

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SECTION A

(Attempt all – 10 × 2 = 20 marks)

Q1(a) IC Engine

An IC (Internal Combustion) engine is an engine in which fuel combustion takes place inside the engine cylinder to produce mechanical power.

Q1(b) Axial Flux

Axial flux refers to a magnetic flux path that flows parallel to the axis of rotation, commonly used in axial-flux electric motors for compact design.

Q1(c) BESS

BESS (Battery Energy Storage System) is a system that stores electrical energy using batteries and supplies power when required.

Q1(d) OCPP

OCPP (Open Charge Point Protocol) is a communication protocol used between EV charging stations and central management systems.

Q1(e) Power Grid

A power grid is an interconnected network for generation, transmission, and distribution of electrical

energy to consumers.

Q1(f) On-board Charging

On-board charging refers to charging the EV battery using a charger installed inside the vehicle, typically through AC supply.

Q1(g) Cell Balancing

Cell balancing is the process of equalizing voltage levels of individual cells in a battery pack to improve safety and battery life.

Q1(h) DC-DC Converter

A DC-DC converter converts one DC voltage level to another DC voltage level required for EV subsystems.

Q1(i) BLDC

BLDC (Brushless Direct Current) motor is an electric motor that uses electronic commutation instead of mechanical brushes.

Q1(j) Aggregator

An aggregator is an entity that manages and coordinates multiple EVs or charging stations for energy management and grid interaction.

SECTION B

(Attempt ANY THREE – 3 × 10 = 30 marks)

Q2(a) Basic Components and Architecture of an Electric Vehicle

An electric vehicle consists of major components such as battery pack, electric motor, power electronics controller, DC-DC converter, on-board charger, transmission system, thermal management system, and vehicle control unit.

The battery supplies electrical energy to the motor through power electronics. The controller regulates speed and torque. The DC-DC converter powers auxiliary loads, while the charger recharges the battery from external power sources. This architecture ensures efficient and emission-free operation.

Q2(b) EV Motor and Classification

An EV motor converts electrical energy into mechanical energy for propulsion.
EV motors are classified as DC motors, BLDC motors, PMSM, induction motors, and switched reluctance motors.
BLDC and PMSM are commonly used due to high efficiency and power density. Induction motors are robust and cost-effective, while SRM offers high reliability.

Q2(c) Battery and Characteristics

A battery is an electrochemical device that stores and supplies electrical energy.

Lead-Acid Battery:
Low cost, heavy weight, low energy density, shorter life cycle.

Lithium-Ion Battery:
High energy density, lightweight, longer life, fast charging, widely used in EVs.

Q2(d) Design Considerations for Charging System

Important design considerations include charging speed, safety, power rating, grid compatibility, thermal management, communication protocol, efficiency, and user convenience.

Q2(e) Scheduling of Energy Generation

Scheduling of energy generation involves planning power production based on demand, availability, and grid constraints to ensure efficient and reliable energy supply.

SECTION C

Q3(a) Recent Trends and Developments in Electric Vehicles

Recent trends include fast-charging technology, solid-state batteries, wireless charging, vehicle-to-grid (V2G) integration, AI-based energy management, lightweight materials, and increased government support for EV adoption.

Q3(b) Comparison of Electric Vehicles and IC Engine Vehicles

Electric vehicles offer zero emissions, higher efficiency, lower operating cost, and quiet operation, whereas IC engine vehicles rely on fossil fuels, produce emissions, and require higher maintenance.

Q4(a) Power Electronics Converters

Power electronics converters control and convert electrical power in EVs.
They include AC-DC converters, DC-DC converters, and inverters. These converters manage voltage,

current, and frequency for efficient motor operation.

Q4(b) BLDC Motor Driving Scheme

BLDC motors are driven using electronic commutation with inverter circuits. Hall sensors detect rotor position, and switching signals control motor phases to achieve smooth rotation.

Q5(a) UN38 Regulation and Li-Ion Pack Reliability

UN38 regulations ensure safe transportation of lithium batteries.
Mechanical and reliability aspects include thermal stability, vibration resistance, insulation, and protective casing of Li-ion packs.

Q5(b) Energy Storage System

Energy storage systems store electrical energy for later use. In EVs, batteries are primary storage systems, supported by supercapacitors and BESS for enhanced performance.

Q6(a) AC and DC Charging & Computing Requirements

AC charging uses on-board chargers and is slower, while DC charging bypasses on-board chargers and enables fast charging.
Computing systems manage charging control, communication, safety, billing, and monitoring.