why maglev essay
MagLev technology is completely different from any form of transport in operation today, but the basic principles that lay at the basis are not over and above the comprehension of the beginning electrical power and magnetism student. It really is in the using these rules to design and optimize a real train that things obtain hairy. The standard idea has become researched because the mid-sixties, but it really is only now that economically feasible prototypes will be being created and government authorities are seriously looking towards magnets to propel us in the next 100 years. Leading the race is definitely Germany. All their design, the Transrapid 07, is looking forward to commercial production. It utilizes conventional electromagnets and causes of appeal to levitate the train. A good web site to find out more about German ideas for their style is http://transrapid.simplenet.com/index-e.htm
Japan are examining an entirely totally in accordance with numerous structure involving superconducting magnets to generate huge repulsive forces which in turn levitate the train. However , their MLU002N is still in experimental stages. For more information, take a look at http://www.rtri.or.jp/rd/maglev_E.html
With a little stretching, the average physics student will be able to comprehend the guidelines of magnet levitation and propulsion through synchronous geradlinig motors. To facilitate the process of understanding this kind of complex materials, we suggest that the student proceed through this website in order. Be sure to understand the simple physics before moving on towards the page which usually applies these principles to magnetically levitated vehicles.
We know by experiment that the moving fee exerts a force on other going charges, we call this effect magnetism. The magnet force is a field push, meaning that a moving fee sets up a field which in turn applies a power on various other moving charges. The discipline set up with a given moving charge is deemed perpendicular to its velocity, and to corrosion with distance from the charge:
1st, we can examine just how magnetic domains are created, then we will calculate their very own magnitude and direction.
A few materials can be said to be normal magnets. These kinds of magnets don’t appear to have any shifting charge, just how can they create magnetic areas? The answer is available at the atomic scale:
Bad particals circling a great atom build small permanent magnetic fields. For most materials, these kinds of fields are aligned within a fairly random manner, in order that all of these tiny fields terminate each other. In a magnet, yet , these areas line up to create a net magnet dipole, in order that the object creates a magnet field inside the surrounding space.
A current is actually a moving charge. Moving fees set up magnetic fields. Hence, a current appears the rational way to make a magnetic discipline. There are two basic setups which can be employed for this goal:
The Biot-Savart Law: to find the magnet field (denoted by the sign B) created by a given current distribution, we have to integrate the field by a given test point, G, due to individual current displacements, ids:
The equation intended for the discipline integral turns out to be a rather difficult one, known as the Biot-Savart Legislation:
Ampres Law: in cetain conditions, this essential can be basic by symmetry. In these situatins, we can use a more fundamental law, called Ampres Rules. This regulation allows the calculation in the field from the amount of current encapsulated by a great arbitrary round trip:
The formula for the magnetic discipline in such a case turns out to be:
One of the two most commonly used permanent magnet field equations is that for the long, direct wire. This equation can be determined from Ampres Law through the following create:
The formula is then extracted as follows:
A solenoid is a tightly wound coil of wire carrying a homogeneous current i: The field inside a solenoid is approximately while shown inside the following picture:
We can determine the field inside a solenoid with in turns every unit duration using Ampres Law:
We now have examined just how magnetic areas are created, and the way to calculate all their magnitude. Next, we will examine the force believed on shifting charges and currents due to magnetic domains.
We can say that a moving charge creates a Permanent magnet Field. We also realize that this field sets up a force in other going charges. This kind of force is definitely perpendicular equally to the permanent magnet field and the velocity with the charge:
Next we will determine how to determine this pressure, and then take a look at an example of particular significance to magnetic levitation: repulsion between parallel wire connections.
For the moving level charge, the magnetic push is proportionate to the magnetic discipline strength and the velocity with the charge. Furthermore, the way of this power is perpendicular to both the velocity as well as the field (direction given by right hand rule). Hence, the magnet force has by:
For the current within a wire, the magnetic force is proportionate to the current, the length of the cable, and the permanent magnet field power. Direction is perpendicular to current direction and permanent magnet field.
As a result, the permanent magnet force formula looks very similar to that for the moving level charge:
The repulsion or attraction between two seite an seite wires features particular importance to permanent magnetic levitation. The setup can be as follows:
In the event the currents stream in the same direction (as shown), the wires entice. If the currents flow in opposite directions, the wire connections repel.
To calculate the force of repulsion, we first compute the field produced by line 1:
Following, we make use of B1 to find the force on wire 2 due to cable 1:
We now know how to identify the force on a moving charge as a result of a permanent magnet field, and the way to determine the force of attraction or perhaps repulsion between two power. Next, we will examine the trend of induced currents, where a changing permanent magnetic field can make a current.
In 1831, Michael Faraday and Frederick Henry done similar experiments that proven the following tendency:
In the above illustration, motion of a magnetic through a line loop induce a current in that wire. Reversing the direction in which the magnetic travels reverses the current way.
In this trial and error setup, beginning or closing switch S induces a momentary current, i. The direction of i once closing the switch is usually opposite the direction when opening the switch.
We can conclude from your previous experiments that a enhancements made on the permanent magnet field by using a current loop produces a great current for the reason that wire. More scientifically, we say that an alteration in magnetic flux (field through a given area) induces a current informed to oppose the difference in flux. Quantitatively, we find the fact that negative charge of enhancements made on flux is usually equal to the electromotive force (EMF) in the wire:
For the coil of N becomes, the caused EMF is a sum of the voltages from each turn:
The course of these caused currents, in accordance to a theory known as Lenz Law, often opposes the change in permanent magnet flux that produced this.
When a huge peice of conducting material moves by using a magnetic field in such a way that the magnetic flux through the materials changes, power are induced in the material:
These power, known as turn currents, might produce ideal or undesirable effects, depending on the situation. Of particular curiosity to permanent magnetic levitation may be the magnetic force produced, which will opposes motion through the permanent magnetic field:
This induced permanent magnet force can be somewhat analgous to frictional forces: this opposes movement in or out of the permanent magnetic field. Inside our example of permanent magnetic levitation, this kind of effect turns into significant, as we will see afterwards.
Now we have examined almost all of the basic electro-physics involved in magnet levitation. In the next section, we will begin applying these physics to the magnetically levitated train.
A maglev train has a system made to provide the push for levitation. Since the levitation system is distinct from the propulsion system, a designer can consider various propulsion systems. One particular propulsion program uses Linear Synchronous Motor (abbreviated while LSMs). Another propulsion system uses Linear Induction Power generators (abbreviated while LIMs). This page focuses on the levitation program that can be used with either sort of propulsion program..
This is a cross part of the Magneplane vehicle and its guideway. This setup accomplishes levitation through repulsion. The propulstion system is not explicity diagrammed through this picture, yet , other sources disclose that the Magneplane system uses a LIM. (Image source: site 338, Geradlinig Motion Electromagnetic Systems. )
Now we will move on to develop equations to style a simple repugnant levitation system.
We will certainly model the levitation program using two separate coils. One coil is area of the vehicle, and carries a household power in the counter-clockwise direction (as viewed from above the coil). The second coil is section of the track, and carries a direct current in the opposing (clockwise) course. In practice, the currents should be quite significant to produce a pressure strong enough to counteract the weight with the train. The resistance of the coils is an extremely important factor when the cost of featuring the power is considered. Smaller resistances allow for even more current to become generated applying less power, making the magnetic discipline induced better. For this reason, it truly is most efficient for the coils to be superconducting. However , the expense of superconducting shelves and magnets is also extensive.
The magnetic field strength for segment STOMACH due the magnetic discipline created simply by segment STOMACH is
The force for the upper cable segment STOMACH due the field made by the lower wire section AB:
The style below shows the direction of FAB, which is saving money vector for the drawing branded FB. FB is verticle with respect to beam AB, as well as the vector W. FB is opposite in direction to Fg, and may balance out the force of gravity.
As there are several straight wires comprising every loop, you will find four pushes acting on the top loop.
Remember that the currents in the two loops happen to be traveling in the same way, which provides a repulsive power. This force provides the lift up, or floating force to get the vehicle.
Out of this simple unit we have explaned how levitating forces are created. We can also point out some further concerns:
? This installation only dealt with the vertical forces working on the educate and assumed that the educate was flat stable. In reality, maglev trains need several means of side to side stabilization to keep the train on the observe, in a method of speaking.
? In many maglev systems, the coil setup isnt quite the same as the model explained. The train carries some coils, and the track includes a flat executing surface. The trains shelves have a present flowing, nevertheless the track executing surface is very passive. The moving educate coils produce a moving magnet field. This changing permanent magnet field, or flux, induces eddy currents in the songs conducting surface area. These activated currents after that act like the track coils in the style we utilized. With this in mind, each of our model remains to be effective pertaining to calculations.
? Our version uses many approximations to help make the mathematics even more concise. A single, in our 1st equation, we all assumed which the segment STOMACH was a great infinitely very long wire. Because of this the computation for B is not really exact.
This page handles the devices involved in a Maglev train that use repulsion as the means for interest.
This is a cross section the Krauss-Maffei experimental car and guideway.
This create uses attractiion for levitation and a LIM intended for propulsion.
(Image source: page 27, Thready Motion Electromagnetic Systems. )
The setup for the attraction strategy is very similar to for the setup intended for the repulsion system, only that the course of current in one of the shelves is corrected, resulting in an attractive force between the coils. Likewise, the coils are located with an extension in the train that wraps within the track.
It is vital to notice that as the space between the two coils lessens, the desirable force raises. Under selected conditions both the coils could get pulled in to direct speak to, eliminating the air gap together. This would be extremely undesirable. As a result engineers who design eye-catching levitation system must make make use of a secondary system that screens the air gap distance and may adjust the magnetic field strength properly. This second system likewise would make the ride more comfortable for people.
The magnetic field power at part AB because of the magnet field produced by portion AB can be
The pressure on the reduce wire part AB because of the field created by the upper line segment ABS:
The picture beneath illustrates the direction of FAB, which can be the green vector on the pulling labeled HUB PAGES. FB can be perpendicular to ray AB, and the vector B. HUB PAGES is reverse in course to Fg, and can balance the power of gravity.
Since you will find four straight wires composed of each trap, there are four forces working on the upper trap.
This appealing force supplies the lift, or perhaps levitating force for the vehicle.
Note that the equations happen to be exactly the same, provided that the setups are different. (That is, in the repulsive case, the vehicle coil was over a track coils. In the appealing case provided on this page, the vehicle coil is under the track coil. )
Geradlinig motors are analogous to conventional (rotary) motors. A Linear Induction Motor, or LIM, may be visualized simply by unrolling an established induction motor unit until it can be flat. This kind of presentation is going to explain the qualitative character of the LIM, without going into the challenging mathematical and physical derivations. We will focus on a three-phase LIM.
A LIM consists of two parts, a stator, and a disc. The stator and brake disc consist of magnetically permeable material such as flat iron. Within the stator, three wires are inlayed. Each wire weaves through the stator within a special periodic pattern. Inside the diagram listed below, the cables are verticle with respect to the plane of the screen.
Each cable is connected to a sinusoidal current supply. The three power are every single 120 deg out of phase with one another. This setup is called a three-phase current source.
The pattern used with a three stage current supply is this: A C B A C B Each letter presents a cable. A and A stand for the wire that holds current Ia. A and A carry the same current, but justification in opposite guidelines. The same conventions apply to B, B and C, C.
This construction is very valuable because it permits the stator to create a shifting magnetic discipline.
This going magnetic field induces power in the brake disc. These induced currents, at any instaneous time, oppose the change in the magnetic field, in accordance with Faradays Law.
These kinds of induced power then connect to the moving magnetic field, resulting in a pressure that moves the disc along with the going magnetic field in the stator.
LIMs have the ability to move the rotor relative to the stator without any physical contact. This kind of drastically decreases wear and tear within the parts involved and gets rid of frictional makes that cause inefficiency.
LIMs have the ability to increase the speed of the rotor from relax up to the acceleration of the shifting magnetic field.
LSMs happen to be structurally nearly the same as LIMs except for one alter. The behavior from the two types of linear power generators is transformed significantly.
The two LIMs and LSMs contain a stator and brake disc. Both have three phase currents weaving through the stator. How LSMs fluctuate is that their rotor features two closely spaced direct current wires spaced regularly while the diagram below reveals.
The moving magnetic discipline is set up, but the caused currents create are much less space-consuming than in the LIM case. A single reason would be that the composition of the rotor may be different: it might be laminated or perhaps consist of a material an excellent source of electrical amount of resistance. The DC currents are definitely the important factor in LSMs. Glance at the diagram under. (Note the fact that position of the rotor and stator happen to be reversed. Likewise note the pattern of wires inside the stator can be described as C B A C B )
From Applied Electromagnetism, webpage 578.
The force acting on the disc DC power due to the monitor flux has a tendency to to move the rotor for the right. (This can be displayed using the proper hand guideline involving the vertical track débordement lines. The horizonal track flux lines do not contribute to the propulsion. )
The position of the DC brake disc currents is very important. In the picture above, the rotor currents coming out of the paper are aligned with the leftmost stator wire that is also coming out of the web page. This makes the maximum force on the brake disc. Now consider what will happen after the diagrams time period:
1 . the rotor can move (in relation to its acceleration and velocity)
2 . the stators permanent magnetic field can move (in relation to the frequency with the three phase currents)
Now, after a small time interal, lets take a look at the comparative positions with the rotor and stator. In the event the alignment can be not the same as the figure, then this force on the rotor are not the maximum. It ought to be clear that the Linear Synchronous Motor works best in its sychronous speed.
Without a doubt, if the brake disc isnt shifting close to the synchronous speed, then the LSM will never move the stator at all!
If the disc is close enough for the synchronous velocity, then the LSM will be able to accelerate the rotor up to the synchronous speed.
Note: the synchronous speed of a LSM can be altered in two key ways:
1 . by different the frequency of the 3 phase power
2 . by various the number of wiring per unit length inside the stator and rotor.
LSMs, just like LIMs, are able to move the rotor in accordance with the stator without any physical contact. This kind of drastically minimizes mechanical put on.
LSMs don’t have the ability to increase the speed of the rotor from relax up to the rate of a quickly moving permanent magnetic field. Therefore Maglev teaches that use LSM must either make the synchronous speed start very gradually and increase slowly or use a extra propulsion system for acceleration.
from Geradlinig Motion Electromagnetic Systems, webpage 26.
The basic physics of permanent magnet lift and electrical steam are the basics behind Maglevs energy efficiency. For example , Maglev consumes per trip about one seventh of the energy used by a Boeing 737-300 for a 125-620 mile trip. In addition , Maglev operation is definitely not dependent upon petroleum for its energy, the electrical power may be derived from other sources. The energy productivity is due to the mechanical productivity resulting from significantly reduced chaffing and less enegry lost as heat inside the operation in the vehicle.
High speed can be an inherent attribute of maglev. Because the operation of the automobile occurs without physical get in touch with, high rates are within technological limitations. Speeds up to 500 kilometers per hour will be possible, with top rates usually limited not simply by physical constraints, but rather simply by economic things to consider. Commercial rail today generally travels at only 200 mls per hour, when Maglev guarantees at lowest a 300 mile each hour top speed. Intended for short trips, Maglev is definitely competitive with short plane flights up to 500 a long way!
Maglev could be utilized to effect a fully automated transportation system, with goods being released on the within seconds of their scheduled time. Merging the stability and velocity advantages, this looks to be a encouraging possibility.
Because lift up and assistance forces happen to be distributed over a large location, contact tensions are at a minima. The Linear Motor allows noncontact propulsion and braking, unlike conventional rail where severe stresses happen from wheel/rail contact through power transfer. A low cost routine service program is a certain benefit associated with this technology.
Drag Makes: Magnetic and Aerodynamic
If a conductor moves through a magnet field, the changing flux induces electric currents as reviewed inside the induction webpage of the Simple Physics section.
These turn currents then simply react with all the magnetic discipline in such a way about brake movement through the field. Due to of this phenomenon, a part of the steam energy is spent counteracting the move force. As the stand from Thready Motion Permanent magnetic Systems shows, the pull force increases as the velocity increases, typically. As a maglev gains acceleration, it requires increasingly more energy only to remain in cruising acceleration.
In addition to the magnetic drag pressure, conventional aerodynamic drag is present. Although equally forms of drag are undesirable in many ways, there are several ways of utlizing them to each of our advantage. The drag causes can help braking mechanism a maglev train quite efficiently. Inside the introduction, there is also a photograph of your Maglev coach with aerodynamic brakes expanded.
Technical Problems A Study inside the Feasibility with the SCM
The major specialized barrier to the mass re-homing of Maglev as a fresh transportation system lies in problems with the superconducting magnets (hereafter SCM) accustomed to levitate and power the trains.
Thus far most Maglev trains include utilized an SCM made of NbTi. The SCM builds up extremely great heat during operation, during which it must be cooled down to four degrees Kelvin to take care of its homes. Liquid helium is usually intended for this goal. The heat side effects are inevitable, and thus technicians have focused on the efficiency of the cooling rather than developing a chillier SCM.
Extreme difficulties lie in the storage space of the helium vapor, plus the reliquification of the vapor once it has absorbed the great heat of the SCM. At the moment, this has been the slowest entrance for improvement in Maglev technology.
The latest thought is the fact using cryorefrigeration techniques which constantly great the magnet without pulsating the helium prove to be one of the most promising. By winding the coolant through tubes adjacent the magnet, an even, constant cooling process will be effected.
This maglev diagram known as the LM-500-01, as well from Thready Motion Magnet Systems, site 338, displays many of the on-ship systems associated with refrigerating the superconducting magnets.
These types of techniques, available today, is limited only by it is tremendous expenditure, which factors toward a bottom line intended for Maglev technology.
Economical factors have traditionally been a huge hurdle to otherwise incredibly promising scientific advances. This kind of certainly wedding rings true while using SCM and Maglev. The superconducting magnets themselves price millions, plus the cooling system technologies associated with the SCMs cost large numbers more. While in the lab the technologies have been completely very interesting, the standard systems have up to now won away, merely as a result of costs.
Essentially, we have to look at the opportunity costs involved to fully come to a conclusion with regards to the efficiency of this technology. Adopting the Maglev system worldwide might have severe costs, but with a tangible compensation over the subsequent 20 years. We would see a particular reduction in working costs and a great jump in productivity, but just after the first investment inside the new technology. SCMs and air conditioning R&D have cost us millions possibly billions of dollars, yet our company is not as however ready to agree to the Maglev system. Feasibility studies conducted by the US Department of Transportation demonstrate a great requirement for the technology, yet not any group ready to invest because of the shear number of R&D us dollars still needed with no real examples of Maglev success through this country.
Judging from the progress of other countries, it is our recommendation which the United States do something toward a larger use of Maglev to reduce its long term the problems and take advantage of the inexpensive operation, stability, and strength efficiency linked to Maglev.
Weve stood within the shoulders of giants, now its time to enumerate all of them…
Weve stood around the shoulders of giants, and after this its a chance to enumerate them…
1 . D. Halliday, L. Resnik & K. Krane, Physics, volume. 2, next ed. John Wiley & Sons Inc., 1992.
2 . Liang Chi Shen and Jin Au Kong, Applied Electromagnetism, 3rd education. PWS Posting Company, 95.
3. I. Boldea and S i9000. A. Nasar, Linear Action and Electromagnetic Systems. David Wiley & Sons Incorporation., 1995.
? The High Speed / Automated Transportation Home Page
? The Argonne National Laboratories Home Page
? The Railway Technical Research Institute
? Magnetbahn: The Unofficial Transrapid Homepage