MAGNETIC LEVITATION TRAIN Submitted in partial fulfillment of the requirements for the award of degree of
BACHELOR OF TECHNOLOGY IN Mechanical ENGINEERING Submitted By:
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United College of Engineering and Management
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Contents 1. Introduction 1.1 Introduction 1 1.2 Technology of Magnetic Levitation 2 1.3 Types of Magnetic Levitation 3-5 1.3.1 Permanent magnet type 3 1.3.2 Electromagnetic type 4 1.3.3 Electrodynamics type 5
2. Working Principle 2.1 Levitation 6 2.2 Propulsion 7 2.3 Stability 8 2.4 Guidance 9
3. Merits and Demerits
CHAPTER 1:- INTRODUCTION Some forces in this world are almost invisible to the naked eye and most peo ple throughout the world do not even know they exist. On one side you could sa y that some of these forces are abstract feelings inside of a human being that have been given namesfrom man. These forces could be things like emotion, guilt, and even ecstasy. On the other side you have solid concrete principles of how the world works. These too have been given names by man, but these principles are not abstract and have solid ground in science. These different principles are things like gravity, electricity, and magnetism. Magnetism has been a part of the earth since the beginning whether people realize it or not. It is due to the magnetism of the earth that the world spins and thus creates things like gravity. The magnetism is created by the processes within the core of the earth. The earth’s iron-ore core has a natural spinning motion to it inside which creates a natural magnetic force that is held constant over the earth. This creates magnetic forces that turn the earth into a large bar magnet. The creation of North and South poles on the earth are due to this field. From this magnetic field, we see things such as the aurora borealis. This is a small electromagnetic storm in the atmosphere which creates a display for all to see. Not only does magnetism provide us with amazing natural d isplays, but it also provides for us amazing applications to society. One of these applications is magnetic levitation. Magnetic levitation uses the concept of a magnets natural repulsion to poles of the same kind. This repulsion has been harnessed and controlled in an environment to help create a system of transportation that is both economically sound and faster than most methods of transportation at this point. In 1965 the Department of Commerce established the High Speed Ground Transportation Act. Most early work on developing Maglev technology was developed
during this time. The earliest work was carried out by the Brookhaven National Laboratory, Massachusetts Institute of Technology, Ford, Stanford Research Institute, Rohr Industries, Boeing Aerospace Co., and the Garrett Corporation. In the United States, though, the work ended in 1975 with the termination of Federal Funding for highspeed ground transportation and research. It was at that time when the Japanese and German developers continued their research and therefore came out with the first test tracks. In 1990, legislative action directed the U.S . Army Corps of Engineers to implement and prepare a plan for a National Maglev program. The Department of Transportation (DOT), Department of Energy (DOE), and the Arm y Corp developed what is known as the National Maglev Initiative which was a two year 25 million dollar program to assess the engineering, economic, environmental and safety aspects of Maglev.
1.1:- TECHNOLOGY OF MAGLEV TRAIN
The creation of magnetic forces is the basis of all magnetic levitation. The creation of a magnetic field can be caused by a number of things. The first thing that it can be caused by is a permanent magnet. These magnets are a solid material in which there is an induced North and South Pole. These will be described further a little later. The second way that a magnetic field can be created is through an electric field changing linearly with time. The third and final way to create a magnetic field is through the use of direct current. There are two basic principles in dealing with the concept of magnetic levitation. The first law that is applied was created by Michael Faraday. This is commonly known as Faraday’s Law. This will allow the direction of the magnetic field to be predictable and thus a set up can be created for a specific purpose to maximize the force that is created.
1.2:-TYPES OF MAGNETIC LEVITATION
1.2.1) Permanent Magnets:The first type of levitation is the implementation through permanent magne ts. These magnets are made of a material that creates a north and a south pole on them. The formal definition of a permanent magnet is “a material that retains its magnetic i
properties after and external magnetic field is removed.” The whole idea behind permanent magnets is that like ends will repel and opposite ends will attract. Permanent magnets require very little if any maintenance. These magnets do not require cryogens or a large power supply for operation. The magnetic field is measured vertically within the bore of the magnet. The main disadvantages of a permane nt magnet are the cost of the magnet itself when put into large scale systems. Another disadvantage is the varying changes in the magnetic field. The ability to control a constant magnetic force from a permanent magnet is an on-going problem in the application of these types of magnets. . Different applications that use these types of magnets can be found in a number of different areas. Examples of these applications are compasses, DC motor drives, clocks, hearing aids, microphones, speedometers, and many more.
Figure 1:Permanent magnet
1.2.2 Electromagnetic type:- The basic idea behind an current through a wire, you can electromagnet is extremely simple. By running electric create a magnetic field. When this wire is coiled around a magnetic material (i.e. metal), a current is passed through this wire. In doing this, the electric current will magnetize the metallic core. By using this simple principle, you can create all sorts of things including motors, solenoids, heads for hard disks, speakers, and so on. An electromagnet is one that uses the same type of principles as the permanent magnet but only on a temporary scale. This means that only when the current is flowing is there going to be an indu ced magnet. This type of magnet is an improvement to the permanent magnet because it allows somebody to select when and for how long the magnetic field lasts. It also gives a person control over how strong the magnet will be depending on the amount of current that is passed through the wire.
Figure 2 Electromagnetic magnets
1.2.3 Electrodynamics type:The ideas presented behind superconductive m agnets are the same principles that are at work in an MRI. Superconductive magnets are the most common of all the magnets, and are sometimes called cry magnets. The idea behind the superconducting magnets is that there is a material which presents no electrical resistivity to electrical current. Once a current has been fed into the coils of this material, it will indefinitely flow without requiring the input of any additional current. The way that a material is able to have such a low resistivity to current is that it is brought to very low temperatures. The temperatures that are commonly found in superconducting o
magnets are around -258 C. This is done by immersing the coils that are holding the current into
liquid Helium; this also helps in maintaining a homogenous magnetic field over time. The advantage to the superconducting magnet is that they don’t require constant power from a source to keep up the value of the current in the coils. Although a disadvantage is that they require an expensive cryogen such as helium to operate correctly. The magnetic field is in the direction of the long axis of the cylinder or bore of the magnet. Since the resistance in the coils can cause the current to decay, cryogens reduce the resistance to almost zero, which will help maintain a homogenous magnetic field over time.
Figure 3 Electrodynamics magnet
CHAPTER2:- WORKING PRINCIPLE
2.1 Levitation:Support electromagnets built into the undercarriage and along the entire length of the train pull it up to the guide way electromagnets, which are called ferromagnetic reaction rails. The guidance magnets placed on each side of the train keep it centred along the track and guide the train along. All the electromagnets are controlled electronically in a precise manner. It ensures the train is always levitated at a distance of 8 to 10 mm from the guide way even when it isn't moving. This levitation system is powered by on-board batteries, which are charged up by the linear generator when the train travels. The generator consists of additional cable windings integrated in the levitation electromagnets. The induced current of the generator during driving uses the Propulsion magnetic field's harmonic waves, which are due to the side e ffects of the grooves of the long stator so the charging up process does not consume the useful propulsion magnetic field. The train can rely on this battery power for up to one hour without an external power source. The levitation system is independent from the propulsion system.
Figure 4: Levitation
2.2 Propulsion:The synchronous long stator linear motor of the Maglev system is used both for propulsion and braking. It is functioning like a rotating electric motor whose stator is cut open and stretched along under the guide way. Inside the motor windings, alternating current is generating a magnetic traveling field which moves the vehicle without contact. The support magnets in the vehicle function as the excitation portion (rotor). Propulsion system in the guide way is activated only in the se ction where the vehicle actually runs. The speed can be continuously regulated by varying the frequency of the alternating current. If the direction of the traveling field is reversed, the motor becomes a gen erator which breaks the vehicle without any contact. The braking energy can be re-used and fed back into the electrical network. The three-phase winded stator generates an electromagnetic travelling field and moves the train when it is supplied with an alternating current. The electromagnetic field from the support electromagnets (rotor) pulls it along. The magnetic field direction and speed of the stator and the rotor are synchronized. The Maglev's speed can vary from standstill to full operating speed by simply adjusting the frequency of the alternating current. To bring the train to a full stop, the direction of the travelling field is reversed. Even during braking, there isn't any mechanical contact between the stator and the rotor. Instead of consuming energy, the Maglev system acts as a generator, converting the breaking energy into electricity, which can be used elsewhere.
Figure 5:Propulsion
2.3 Stability:For successful levitation and control of all 6 axes (degrees of freedom; 3 translational and 3 rotational) a combination of permanent magnets and electromagnets or diamagnets or superconductors as well as attractive and repulsive fields can be used. From Earns haw’s theorem at least one stable axis must be present for the system to levitate successfully, but the other axes can be stabilized using ferromagnetism. Static stability means that any small displacement away from a stable equilibrium causes a net force to push it back to the equilibrium point. Earns haw’s theorem proved conclusively that it is not possible to levitate stably using only static, macroscopic, paramagnetic fields. The forces acting on any paramagnetic object in any combinations of gravitational, electrostatic, and magneto static fields will make the object's position, at best, unstable along at least one axis, and it can be unstable equilibrium along all axes. However, several possibilities exist to make levitation viable, for example, the use of electronic stabilization or diamagnetic materials (since relative magnetic permeability is less than one); it can be shown that diamagnetic materials are stable along at least one axis, and can be stable along all axes. Conductors can have a relative permeability to alternating magnetic fields of below one, so some configurations using simple AC driven electromagnets are self-stable. Dynamic stability occurs when the levitation system is able to damp out any vibration-like motion that may occur.
Magnetic fields are conservative forces and therefore in principle have no built-in damping, and in practice many of the levitation schemes are under-damped and in some cases negatively damped. This can permit vibration modes to exist that can cause the item to leave the stable region.
Figure 6 :Stability
2.4 Guidance:Electronically controlled support magnets located on both sides along the entire length of the vehicle pull the vehicle up to the ferromagnetic stator packs mounted to the underside of the guide way. Guidance magnets located on both sides along the entire length of the vehicle keep the vehicle laterally on the track. Electronic systems guarantee that the clearance remains constant (nominally 10 mm). To hover, the Maglev requires less power than its air conditioning equipment. The levitation system is supplied from on-board batteries and thus independent of the propulsion system. The vehicle is capable of hovering up to one hour without external energy. While travelling, the on-board batteries are recharged by linear generators integrated into the support magnets. The Maglev hovers over a double track guide way. It can be mounted either at grade or elevated on slim columns and consists of individual steel or concrete b eams up to 62 m in length. Guidance or steering refers to the sideward forces that are required to make the vehicle follow the guide wa y. The necessary forces are supplied in an exactly analogous fashion to the suspension forces, either attractive or repulsive. The same magnets on board the vehicle, which supply lift, can be used
concurrently for guidance or separate guidance magnets can be used. They use Null Flux systems, also known as Null Current systems, this use a coil which is wound so that it enters two opposing, alternating fields. When the vehicle is in the straight ahead position, no current flows, but if it moves off-line this creates a changing flux that generates a field that pushes it back into line.
Figure 7: Guidance
CHAPTER3:- MERITS AND DEMERITS With that we come to the core issue, the pros and cons of the Maglev Train System that need to be taken into consideration in order to determine whether it is really feasible when it comes to the United States. Basically, the practice tracks are already in place in different parts of the world; the US in no exception. More importantly, the Maglev Train System has already tasted success in various countries, including Japan and China. On the basis of the performance of existing maglevs, which include the ones that are in service as well as the ones which are being tested, we were able to come up with the following advantages and disadvantages of the system.
MERITS The foremost advantage of maglev trains is the fact that it doesn't have moving parts as conventional trains do, and therefore, the wear and tear of parts is minimal, and that reduces the maintenance cost by a significant extent. More importantly, there is no physical contact between the train and track, so there is no rolling resistance. While electromagnetic drag and air friction do exist, that doesn't hinder their ability to clock a speed in excess of 200 mph. Absence of wheels also comes as a boon, as you don't have to deal with deafening noise that is likely to come with them Maglevs also boast of being environment friendly, as they don't resort to internal co mbustion engines. These trains are weather proof, which means rain, snow, or severe cold don't really hamper their performance. Experts are of the opinion that these trains are a lot safe than their conventional counterparts as they are equipped with state-of-the-art safety systems, which can keep things in control even when the train is cruising at a high speed.
DEMERITS while the advantages of Maglev Train S ystem may seem quite promising in themselves, they are not enough to overshadow the biggest problem with the maglev trains: the high cost incurred on the initial setup. While the fast conventional trains that hav e been introduced of late, work fine on tracks which were meant for slow trains, maglev trains require an all new set up right from the scratch. As the present railway infrastructure is of no use for maglevs, it will either have to be replaced with the Maglev System or an entirely new set up will have to be created―both of which will cost a decent amount in terms of initial investment. Even though inexpensive as compared to EDS, it is still expensive compa red to other modes.
If the advantages and disadvantages of these trains are pitted against each other, it can be a bit difficult to come to a concrete conclusion. While the high cost of initial set up is something that a developed nation like the United States won't have to worry about, the fact that the entire infrastructure has to be replaced with a new one will be something that will have the experts in a catch-22 situation. But obviously, we will have to do away with their disadvantages if we are to invest in maglev trains. If the commercial success of the Shanghai maglev train is to be taken into consideration, these trains can be surely considered the transport system of the future.
