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Maglev Trains And The Technology Behind Them (magnetism)

Extracts from this document...

Introduction

Maglev Trains And The Technology Behind Them

Introduction

Magnets

Magnetism is a phenomenon that occurs when a moving charge exerts a force on other moving charges. The magnetic force caused by these moving charges sets up a field which in turn exerts a force on other moving charges. This magnetic field is found to be perpendicular to the velocity of the current. The force of the field decays with distance from the charge. Most magnets we come across are weak permanent magnets, such as fridge magnets and door catches. A permanent magnet is a material that is naturally magnetic, they set up magnetic fields by electrons circling an atom setting up magnetic fields.  They are based on oxides of barium and iron. They have low field strength and would not be strong enough for use in Maglev trains. Lately, developments in magnet research have found rare earth-permanent magnets that have a much stronger magnetic field. These new magnets have become an important part of our everyday life being used in many everyday applications such as computers, CD players and mobile phones. It is these high performance magnets that are used in Maglev trains. The rare earth elements are scandium 21, yttrium 39 and lanthanide’s 57-71.

The principle of a Maglev (Magnetic Levitation) train is that it floats on a magnetic field and is propelled by a linear induction motor. They follow guidance tracks with magnets and have been seen to have great potential in the transport world.

An example of a maglev train from http://www.newscientist.comimage04.png

Simple Theory

A maglev train will float about 10mm above the guideway on a magnetic field. It is propelled not by an onboard engine, but by the guideway itself by changing the magnetic field of the electromagnets along the length of the guideway.

...read more.

Middle

The EDS or Electrodynamics Suspension is the other system in design and acts on the theory of repulsion rather than attraction. It does not require the constant electric control of the gap like the EMS as the system is inherently stable.

In the EDS-repulsive system, the superconducting magnets levitate of the vehicle, are at the bottom of the vehicle, but above the track. A phenomenon know as the Meisner effect is exploited where superconductors are used to levitate magnets above. The track is either an aluminium guideway or a set of conductive coils. The magnetic field of the superconducting magnets aboard the maglev vehicle induces an eddy current in the guideway. The polarity of the eddy current is same as the polarity of the Superconducting magnets onboard the vehicle. Repulsion results, "pushing" the vehicle away and thus up from the track. The gap between vehicle and guideway in the EDS-system is considerably wider than the EMS at 1 to 7 inches.

When a magnet moves beside a conductor, the magnetic field inside the conductor will change and a current will be induced. The induced current in turn generates a magnetic field which, according to Lenz's Law that an induced electric current always flows in such a direction that it opposes the change producing it, tends to resist the change that caused the induction. Lenz’s law was an advancement from Faraday’s law which stated the magnitude of the e.m.f. induced in a conductor equals the rate of change of flux linkages or the rate at which the conductor cuts a magnetic flux. The method of EDS utilizes the principle of electromagnetic induction.  The train travels in a guideway which has a series of 8 shaped coils on each side.

...read more.

Conclusion

Bibliography

http://www.calpoly.edu/~cm/studpage/clottich/fund.html

Used for Advantages, disadvantages, drift correction, basic motor information. Not used for advanced physics

http://members.aol.com/marctt/Research/chapter1.htm

Very small amount of info about different types of Maglev

http://www.alcyone.com/max/physics/laws/index.html

Used for Lenz Law info

http://www.howstuffworks.com/maglev-train.htm

Very basic information

http://www.amlevtrans.com/diagram3.htm

V=2fLw equation

http://ntl.bts.gov/DOCS/TNM.html

Small amounts of advanced information on the working of maglev Trains

http://www.dom.com/about/companies/vapower/maglev/future.jsp

Very little useful information

http://faculty.washington.edu/~jbs/itrans/maglevq.htm

Links to other sites

www.magnemotion.com/technology/Maglev/pdf/M3UrbanSystem.pdf

Extensive 40 page pdf file, used for some useful information but to much about specific project and its testing.

http://www.rtri.or.jp/rtri/rtri_E.html

Info on Japanese Maglev project and its history

http://www.hfml.kun.nl/levitation-possible.html

Earnshaw theorem information

http://www.hk-phy.org/articles/maglev/maglev_e.html

Good site with very good information and pictures

http://www.superconductors.org/

Basic superconductor information

http://inventors.about.com/library/inventors/blrailroad3.htm

Used for very small amount of info

http://members.tripod.com/~american_almanac/maglev.htm

Used for a lot of useful information about the workings of Maglev. Not much physics in it.

http://www.monorails.org/tMspages/TPMagIntro.html

Useful site giving me the clear definitions between EDS and EMS as well as pictures

http://www.transrapid.de/

Used for info and history on German and Chinese projects.

Advancing Physics A2 book.

Used for equations for magnets and information on electromagnets

www.trymegaessays.com

Used for information of superconductor problems detailed magnet theory and maglev information. Not written well too confusing.

Physics World magazine

Used for initial info Maglev

Encyclopaedia Britannica 11

Used for small amount of advanced info on magnets. Repulsion picture

http://math.ucr.edu/home/baez/physics/General/Levitation/levitation.html

Earnshaw theorem info

The Complete A-Z of Physics handbook

Equations and magnet theory

...read more.

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