(SEM VI) THEORY EXAMINATION 2022-23 ELECTRIC AND HYBRID VEHICLES

ELECTRIC AND HYBRID VEHICLES – KEE-064

Section-wise Important Questions & Ready Answers

SECTION A

(Attempt all questions in brief – 2 marks each)

(a) Social and Environmental Advantages of Electric and Hybrid Vehicles

Electric and hybrid vehicles significantly reduce air pollution by producing little or no tailpipe emissions. They help in lowering greenhouse gas emissions, reducing dependence on fossil fuels, minimizing noise pollution, and improving public health. Socially, they promote energy security and sustainable transportation.

(b) Brief History of Hybrid and Electric Vehicles

Electric vehicles were developed in the late 19th century but declined due to the rise of internal combustion engines. Interest revived in the late 20th century due to fuel crises and environmental concerns. Hybrid vehicles emerged as a bridge technology combining ICE and electric propulsion for better efficiency.

(c) Electric Components Used in Hybrid and Electric Vehicles

Major electric components include electric motors, power electronic converters, energy storage systems (batteries, ultracapacitors), controllers, onboard chargers, and DC-DC converters. These components enable propulsion, energy conversion, and control.

(d) Drive System Efficiency in Hybrid and Electric Vehicles

Drive system efficiency depends on motor efficiency, inverter performance, transmission losses, and control strategy. Electric drivetrains are generally more efficient than conventional drivetrains due to fewer mechanical losses.

(e) Energy Storage Requirements in Hybrid and Electric Vehicles

Energy storage systems must have high energy density, high power density, long life, fast charging capability, safety, and reliability. They should support regenerative braking and meet vehicle range requirements.

(f) Advantages and Challenges of Battery-Based Energy Storage

Batteries offer high efficiency, zero emissions at use, and flexibility. Challenges include limited energy density, long charging time, degradation over time, thermal management issues, and high cost.

(g) Sizing of Power Electronics Devices

Power electronic devices are sized based on voltage rating, current rating, thermal limits, switching frequency, efficiency, and safety margins. Proper sizing ensures reliability and performance of the propulsion system.

(h) Role of Communications in Hybrid and Electric Vehicles

Communication systems enable data exchange between sensors, controllers, battery management systems, and vehicle control units. They support diagnostics, safety, energy management, and vehicle-to-vehicle or vehicle-to-infrastructure communication.

(i) Implementation Issues in Energy Management Strategies

Key issues include computational complexity, real-time constraints, uncertainty in driving conditions, battery aging, and trade-offs between efficiency and performance.

(j) Key Factors Influencing Energy Management

Driving cycle, battery state of charge, vehicle load, road conditions, driver behavior, and component efficiency influence energy management decisions.

SECTION B

(Attempt any three – 10 marks each)

2(a) Vehicle Performance and Power Source Characterization

Vehicle performance depends on traction force, aerodynamic drag, rolling resistance, and road gradient. Power sources are characterized by torque-speed characteristics, efficiency maps, and dynamic response. Mathematical models relate engine power, transmission ratio, and vehicle speed to evaluate performance.

2(b) Permanent Magnet Motor Drives in EVs and HEVs

Permanent magnet motors offer high efficiency, high power density, and excellent torque characteristics. Their control involves inverter-based voltage and current control using field-oriented control to achieve precise torque and speed regulation.

2(c) Comparison of Battery-Based Energy Storage Systems

Lead-acid batteries are low-cost but heavy. Nickel-metal hydride batteries offer better energy density and durability. Lithium-ion batteries provide high energy density, long life, and fast charging, making them most suitable for modern EVs.

2(d) Selection of Energy Storage Technology

Selection depends on energy density, power density, lifecycle cost, safety, operating temperature, and application requirements. Trade-offs are evaluated to match vehicle performance and cost targets.

2(e) Energy Management Strategies Comparison

Rule-based strategies are simple but less optimal. Optimization-based strategies offer better efficiency but require high computation. Learning-based strategies adapt to driving patterns but need extensive data.

SECTION C

3(a) Electric Traction and Drive-Train Topologies

Electric traction uses electric motors to generate driving force. Drive-train topologies include single-motor, dual-motor, and in-wheel motor configurations. Power flow control manages energy between battery, motor, and regenerative braking to maximize efficiency.

3(b) Hybrid Traction and Drive-Train Topologies

Hybrid traction combines ICE and electric propulsion. Series, parallel, and series-parallel configurations control power sharing between engine and motor to improve fuel efficiency and reduce emissions.