Hydrogen Super Highway

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  • Topic: Electromagnet, Magnetic field, Magnet
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  • Published : September 29, 2012
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Prashant Zanwar

University of Central Florida

I. Introduction To Maglev Technology And Application
1.1 Principle of Maglev System
Maglev is a system in which the vehicle runs levitated from the guideway (corresponding to the rail tracks of conventional railways) by using electromagnetic forces between superconducting magnets on board the vehicle and coils on the ground. The following is a general explanation of the principle of Maglev.

fig. 1.1

1.1.1 Magnetic Levitation
The "8" figured levitation coils are installed on the sidewalls of the guideway. When the on-board superconducting magnets pass at a high speed about several centimeters below the center of these coils, an electric current is induced within the coils, which then act as electromagnets temporarily. As a result, there are forces which push the superconducting magnet upwards and ones which pull them upwards simultaneously, thereby levitating the Maglev vehicle.

fig. 1.2

1.1.2 Lateral Guidance
The levitation coils facing each other are connected under the guideway, constituting a loop. When a running Maglev vehicle, that is a superconducting magnet, displaces laterally, an electric current is induced in the loop, resulting in a repulsive force acting on the levitation coils of the side near the car and an attractive force acting on the levitation coils of the side farther apart from the car. Thus, a running car is always located at the center of the guideway.

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fig. 1.3

1.1.3 Propulsion
A repulsive force and an attractive force induced between the magnets are used to propel the vehicle (superconducting magnet). The propulsion coils located on the sidewalls on both sides of the guideway are energized by a three-phase alternating current from a substation, creating a shifting magnetic field on the guideway. The on-board superconducting magnets are attracted and pushed by the shifting field, propelling the Maglev vehicle.

1.1.4 Floatation
The electrodynamics, repulsion-type maglev system, originally patented by American scientists in the 1960s, is the focus of the development program of the Japan Railway Technical Research Institute. In this approach, levitation magnets on the top of a guideway or as is the case with present Japanese prototype designs, in the guideway sidewalls push away superconducting magnets grouped underneath or at the bottom sides of the vehicles. Linear synchronous propulsion coils in the guideway propel the vehicles. This type of system allows for a large air gap (about 15 cm) between opposing magnets. In the electromagnetic, or attraction-type, Maglev developed by Transrapid International in Germany, conventional iron-core magnets in the vehicle's wraparound arms are pulled up to magnets under the guideway. A relatively small air gap (1 cm) separates the vehicle and guideway magnets. Although not part of the present Transrapid design, superconducting magnets can be incorporated in attraction-type Maglev systems.

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fig. 2.1

1.1.5 Maglev Technology Some Facts
Q. How does low-speed Maglev technology work? A. Maglev technology employs powerful superconducting magnets to levitate or "float" cars about 2 inches above a guideway. Liquid helium in a special encasement cools the magnets to near absolute zero (or about -400 degrees Fahrenheit), enabling relatively small magnets to create very powerful fields. Linear induction motors using magnetic fields propel the cars. Such motors are already adapted to transit, such as in Vancouver’s automated SkyTrain Light Rail system. Electrodynamics involving the interaction of electrical currents and magnetic forces, state-of-art computers and microprocessors maintain guidance (vertical and horizontal spacing) during travel. Low-speed Maglev travels up to 60 mph. In Pittsburgh’s case, top speed will be about 40 mph. Q. Why do the superconducting magnets have to be super-cooled? A. It’s a matter of complex physics. But by bathing superconducting magnetic coils in...
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