Introduction to Electric and Hybrid Vehicles

Unit 8

1. Write a note on Electric vehicles. (June 2015)

Solution: - EVs use an electric motor (or traction, and chemical batteries, fuel cells, ultra Capacitors, and/or flywheels for their corresponding energy sources. The EV has many advantages over the conventional internal combustion engine vehicle ICEV, such as absence of emissions, high efficiency, independence from petroleum, and quite and smooth operation. The operational and fundamental principles in Eva and ICEVs are similar, as described in Chapter2. There are. However, some differences between ICEVs and EVs, such as the use of a gasoline tank versus batteries, ICE versus Settle motor, and different transmission requirements. The methodology power train design and will investigate the key components. Including traction motor, energy storage, and soon.

2. Explain the tractive effort and discuss the performance characteristics of electric vehicles. (June 2015)

Solution: - 3. Write a note on hybrid vehicles. (Dec 2014) Solution: - Hybrid technology redirects here. For the company formerly known as Hybrid Technologies, Li-ion Motors. The Toyota Prius is the world's top selling hybrid.

A hybrid vehicle is a vehicle that uses two or more distinct power sources to move the vehicle The term most commonly refers to hybrid electric vehicles (HEVs), which combine an internal combustion engine and one or more electric motors. However, other mechanisms to capture and utilize energy are included.

In a parallel hybrid bicycle human and motor power are mechanically coupled at the pedal drive train or at the rear or the front wheel, e.g. using a hub motor, a roller pressing onto a tire, or a connection to a wheel using a transmission element. Human and motor torques are added together. Almost all manufactured Motorized bicycles, Mopeds are of this type.

In a series hybrid bicycle (SH) the user powers a generator using the pedals. This is converted into electricity and can be fed directly to the motor giving a chainless bicycle but also to charge a battery. The motor draws power from the battery and must be able to deliver the full mechanical torque required because none is available from the pedals. SH bicycles are commercially available, because they are very simple in theory and manufacturing. The first known prototype and publication of an SH bicycle is by Augustus Kinze in 1975. In 1994 Bernie MacDonald’s conceived the Electrolyte SH lightweight vehicle which used power electronics allowing regenerative braking and pedaling while stationary. In 1995 Thomas Muller designed a "Fahrrad mit electro magnetism Antrieb" in his 1995 diploma thesis and built a functional vehicle. In 1996 Jürg Blatter and Andreas Fuchs of Berne University of Applied Sciences built an SH bicycle and in 1998 mounted the system onto a Leitra tricycle (European patent EP 1165188). In 1999 Harald Kutzke described his concept of the "active bicycle": the aim is to approach the ideal bicycle weighing nothing and having no drag by electronic compensation. Until 2005 Fuchs and colleagues built several prototype SH tricycles and quadricycles .

4. Explain the construction and working principle of a linear induction motor.

(June /July 2014)

Solution: - Linear Induction motor abbreviated as LIM, is basically a special purpose motor that is in use to achieve rectilinear motion rather than rotational motion as in the case of conventional motors. This is quite an engineering marvel, to convert a general motor for a special purpose with more or less similar working principle, thus enhancing its versatility of operation.

Let us first look into the construction of a LIM. Construction wise a LIM is similar to three phase induction motor If the stator of the poly phase induction motor shown in the figure is cut along the section aob and laid on a flat surface, then it forms the primary of the LIM housing the field system, and consequently the rotor forms the secondary consisting of flat aluminium conductors with ferromagnetic core for effective flux linkage. There is another variant of LIM also being used for increasing efficiency known as the double sided linear induction motor. 5. What is hybrid vehicle? Explain configuration and performance of hybrid vehicle.

(June /July 2014)

Solution: - Conventional vehicle with IC engines provide good, performance and king operating range by utilizing the 'high-energy density advantages of petroleum fuels. However, conventional IC engine vehicles have the disadvantage of poor fuel economy and environmental pollution. The main reasons for their poor fuel economy are

(I) mismatch of engine fuel efficiency characteristics with the real operation requirement and

(2) Dissipation of vehicle kinetic energy during braking, especially while operating in urban areas;

(3) Low efficiency of hydraulic transmission in current automobiles in stop and-go driving patterns. Battery powered EVs, on the other hand, possess some advantages over & conventional IC engine vehicles, such as high-energy efficiency and zero environmental pollution. However, the performance, especially the operation range per battery charge, is far less competitive than IC engine vehicles, due to much lower energy density of the batteries than that of gasoline. HEVs, which uses two power sources (a primary power source and a secondary power ), have the advantages of both IC engine vehicles Mel EVs and over-come their disadvantages.

Concept of Hybrid Electric Drive Trains: Basically, any vehicle power train is required to (I) develop sufficient power Jaime the demands of vehicle performance, (2) carry sufficient energy on-Egad to support the vehicle driving a sufficient range, (3) demonstrate high efficiency, and (4) emit few environmental pollutants. Broadly. a vehicle may heve more than one power train. Here, the power train is defined as the combination of the energy source and the energy converter or power source, such as gasoline (or diesel heat engine system, the hydrogen-fuel cell. Electric motor system. the chemical battery-electric motor system, and so on. A vehicle that has two or more power trains Is called s hybrid vehicle. A hybrid vehicle electrical power train Is called an HEV. The drive train of a vehicle is defined as the aggregation of all the power trains.

6. Write a note on tramways and trolley buses. (June /July 2014) Solution: - Trackless trolley"redirectshere. For the non-electric buses that resemble historic streetcars, see Tourist trolley

A trolleybus (also known as trolley bus, trolley coach, trackless trolley, trackless tram [in early years] or trolley) is an electric bus that draws its electricity from overhead wires (generally suspended from roadside posts) using spring-loaded trolley poles. Two wires and poles are required to complete the electrical circuit. This differs from a tram or streetcar, which normally uses the track as the return part of the electrical path and therefore needs only one wire and one pole (or pantograph). They also are distinct from other kinds of electric buses, which usually rely on batteries. Currently, around 300 trolleybus systems are in operation, in cities and towns in 43 countries. Altogether, more than 800 trolleybus systems have existed, but not more than about 400 concurrently.

Tramways are lightly laid railways, sometimes worked without locomotives. The term is in common use in the United Kingdom, Australia, New, and elsewhere. In New Zealand, they are commonly known as bush tramways. They generally do not carry passengers, although staff may make use of them, either officially or unofficially.

Tramways can take many forms, sometimes just tracks laid on the ground to move materials around a factory, mine or quarry. At the other extreme they could be complex and lengthy systems, such as the Lee Moor Tramway in Devon. Many are narrow gauge. Motive power can be manual, animal (especially horses), stationary engine, or small locomotives.

7. Compare electric vehicles over conventional internal combustion engine vehicles.

(Dec 2013)

Solution: - The electrical vehicles have the following advantages over internal combustion engine vehicles.

1. It is the cleanest drive as there are no any type of emissions and most suitable for underground railways.

2. It has high efficiency of operation. 3. The vibrations during. motion are less and hence the run is quiet and smooth. 4. The haulage capacity is more and can withstand large temporary loads. 5. An EV has high values of acceleration and braking retardation and hence, can run at high speeds. 6. The maintenance and repairs are less. However, the greatest disadvantage of electric traction is that it involves heavy initial expenditure for the erection of power supply system.

8. With a relevant graph explain traction motor characteristics. (Dec 2013) Solution: -

Variable-speed electric motor drives usually have the characteristics shown in Fig. 7.4. At the low-speed region (less than the base speed as marked in Fig.7.4), the motor has a constant torque. In the high-speed region (higher than the base speed). the motor has a constant power. This characteristic is usually represented by a speed ratio x. defined as the ratio of its maximum speed to its base speed. In low-speed operations, voltage supply to the motor increases with the increase of the speed through the electronic converter Mile the flux is kept constant.

At the point of base speed, the voltage of the motor reaches the source voltage. After the base speed, the motor voltage is kept constant and the flux is 'wakened, dropping hyperbolically with increasing speed. Hence, its torque also drops hyperbolically with increasing speed.

Figure 7.5 shows the torque-speed profiles of a 60 kW motor with different speed ratios x (x = 2, 4, and 6). It is clear that with a long constant power region, the maximum torque of the motor can be significantly increased, and hence vehicle acceleration and grade ability performance can be improved and the transmission can be simplified.

However, each type of motor inherently has its limited maximum speed ratio. For example, a permanent magnet motor has a small x (< 2) because of the difficulty of field weakening due to the presence of the Wet. Switched reluctance motors may achieve x > 6 and induction motors.