maglev trains
... ODU’s maglev train. EDS system: repels the vehicle away from the guideway, using super-conducting magnets. The "8" figured levitation coils are installed on the side-walls of the guideway. When the on-board super-conducting magnets pass at a high speed an electric current is induced within the coils, which then act as electromagnets temporarily. As a result, there are forces, which push the super-conducting magnet upwards, and ones, which pull them upwards simultaneously, thereby levitating the Maglev vehicle. In this system, the levitation takes place only after a certain speed (about 100kph), called the lift-off speed is attained. Therefore for initial rolling, rubber wheels are provided. This offers an advantage in not requiring any electricity backup system. It is a Japanese design and is still in the testing stage. Principle of 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. This results 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. Principle of 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 side walls on both sides of the guideway are energized by a three-phase alternating current from a substation. These propulsion coils are basically stator windings of a linear induction motor. They create a travelling magnetic field on the guideway. The on-board superconducting magnets are attracted and pushed by the shifting field, propelling the Maglev vehicle. General Aspects of Maglev Trains SUPERCONDUCTING MAGNETS: Niobiumtitanium (NbTi) superconductors immersed in liquid helium coolant near its boiling point of 4.2 K. cryogenic refrigerators are used to re-liquefy the helium vapor. SPEED CONTROL: Linear motors can smoothly change the train speed by varying the voltage and frequency of the current supplied to the motors. TILTING: on curved paths the vehicle tilts due to centrifugal force. Tilting enables a vehicle to maintain good comfort ride at higher speeds through turns. Tilting reduces the energy needed to accelerate the vehicle back to cruise speed following the turn. CONSTANT GAP MAINTENANCE: A gap sensor measures the gap (distance between the rail and magnet cores) and an electronic circuit amplifier functions to control the current to the electromagnets or superconducting coils in order to keep the gap at desired level. GUIDEWAY CONSTRUCTION: The guideway consists of a structure corresponding to the conventional track and ground coils. They may be U-shaped or T-shaped depending on the levitation system used. Maglevs require modular construction of these vehicle guideway with prefabricated composite tubular box beams, piers and footings. Advanced materials can extend the lifetime of the system to 100 years with nominal maintenance required. Advantages of Maglev over high speed trains and air travel High speed: Since lift, guidance, and propulsion occur without physical contact, speeds in excess of 220 meters per second (500 miles per hour) are well within the technological limits. Limiting the top speed of Maglev is a cost tradeoff decision, not a physical or engineering limit. By comparison, typical commercial high speed rail reaches only about 83 meters per second (200 miles per hour), a speed that could be slowly increased but only through substantial investment in research and development. Low Wear and Maintenance: By nature, magle...