Electromagnetic suspension: Difference between revisions
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Revision as of 02:00, 27 September 2010
Electromagnetic Suspension (EMS) is the magnetic levitation of an object achieved by constantly altering the strength of a magnetic field produced by electromagnets. Magnetic levitation technology is important because it reduces energy consumption. It also increases energy efficiency by minimizing the contact points between frictional surfaces. The application of magnetic levitation is most commonly known for its role in Maglev trains.
A charged body cannot rest in stable equilibrium when placed in a pure electrostatic field or magnetostatic field. In these kinds of fields an unstable equilibrium condition exists.
Although static fields cannot give stability, EMS works by continually altering the current sent to electromagnets to change the strength of the magnetic field and allows a stable levitation to occur. Usually, a feedback loop which continuously adjusts one or more electromagnets to correct the object's motion is used to cancel the instability.
Many systems use magnetic attraction pulling upwards against gravity for these kinds of systems as this gives some inherent lateral stability, but some use a combination of magnetic attraction and magnetic repulsion to push upwards.
History
Samuel Earnshaw was the one to discover in 1839 that “a charged body placed in an electrostatic field cannot levitate at stable equilibrium under the influence of electric forces alone”.[1] Likewise, due to limitations on permittivity, stable suspension or levitation cannot be achieved in a static magnetic field with a system of permanent magnets or fixed current electromagnets. Braunbeck’s extension (1939) states that a system of permanent magnets must also contain diamagnetic material or a superconductor in order to obtain stable, static magnetic levitation or suspension.[2]
Emile Bachelet applied Earnshaw’s theorem and the Braunbeck extension and stabilized magnetic force by controlling current intensity and turning on and off power to the electromagnets at desired frequencies. He was awarded a patent in March 1912 for his “levitating transmitting apparatus” (patent no. 1,020,942).[3] His invention was first intended to be applied to smaller mail carrying systems but the potential application to larger train-like vehicles is certainly apparent.
In 1934 Hermann Kemper was the one to apply Bachelet’s concept to the large scale, calling it “monorail vehicle with no wheels attached.” He obtained Reich Patent number 643316 for his invention and is also considered by many to be the inventor of maglev.
Background
Electromagnets
(see main article “Electromagnet”)
When a current is passed through a wire, a magnetic field around that wire is generated. When the current to the wire stops, so does the previously generated magnetic field. The strength of the generated magnetic field is directly proportional to the strength of the current sent to the wire. When a wire is coiled, its generated magnetic field is concentrated through the center of the coil. A current through the center of a coil can be greatly increased in strength by placing ferromagnetic material through the center of the coil.
Although a continuous supply of electric current is required to maintain a magnetic field in an electromagnet, this field is easily manipulated by changing the current in the wire. Therefore, electromagnets are much more practical than permanent magnets for levitation purposes. .[4]
Applications
Maglev
Maglev (Magnetic levitation) is a transportation system in which a vehicle is suspended on a guiding rail by the principle of electromagnetic suspension. Maglev has the advantages of being quieter and smoother than wheeled transportations due to the elimination of much of the physical contact between wheels and track. Since Maglev requires a guiding rail, it is mostly used in railed transport systems like trains.
After the first commercial Maglev train was opened in Birmingham, England in 1984, other Maglev train systems, such as JR-Maglev (Japan), M-Bahn (Germany), Shanghai Maglev Train (China) were developed over the past few decades.
Electromagnetic Suspension Device for wheeled transports
WP:STUB 24.184.234.24 (talk) 02:00, 27 September 2010 (UTC)LeucineZipper
Spaceship Launch Aid
NASA has been developing a launch aid using a magnetic levitation system to propel a spaceship. Maglev launch aid saves on design and launching costs, while providing a safer launching method.[5]
See also
References
- ^ B V Jayawant. In Atsugi Unisia Corporation, Brighton BNl 9QT, UK. School of Engineering and Applied Sciences, University of Sussex. Electromagnetic Suspension and Levitation.
- ^ K.X. Quian, P. Zeng, W.M. Ru, H.Y. Yuan (2005) New Concepts and new design of permanent maglev rotary artificial heart blood pumps, Medical Engineering & Physics 28(2006) 383-388
- ^ Bachelet's 1912 patent 1,020,942
- ^ B V Jayawant. In Atsugi Unisia Corporation, Brighton BNl 9QT, UK. School of Engineering and Applied Sciences, University of Sussex. Electromagnetic Suspension and Levitation.
- ^ 21st century launch VehiclesMagLev tested as launch AIf.(1999/12/13). Aviation Week & Space Technology, 151(24), 78.
External links
BOSE Electromagnetic Suspension: