Whether the magev have superconductors which repel the guide base magnetic field or the train have electromagnets opposite to guide way to repel it from the guide way?it is obvious that the guide way have electromagnets but i am confused about the train. Which one is correct?if the train have superconductors then how the propulsion system actually works in that train? How it gets the thrust?
There can be (a) train-borne superconductors for large-gap (10cm) designs (Japanese) or, alternatively, (b) train-borne electromagnets for small gap (1cm) designs (Germans, Chinese). In either case, the magnets can be used for levitation, guidance and propulsion. The thrust comes from an active track, that is coils in the guideway are sequentially excited (like a linear motor) to pull and push on the train superconductors or electromagnets. There are many possible magnetic configurations.
Both configurations can be used, but the closer you get the train to the "rail" the better because you can increase velocity. Recently a new configuration has emerged, creating a vacuum between the entire system, between the surface of the train and its environment, the tunnel. This eliminates the air resistance and allows for extreme speeds, thousands of miles per hour. The downsides of this are: tiny bits of debris can rip through the train leading to explosive decompression; additionally, if the tunnel breeches to the open environment around it allowing air molecules to penetrate the system there would be an extreme acceleration towards 0, and this would act much like an object hitting the atmosphere burning up. Potentially acting similar to an asteroid hitting a thicker layer of atmosphere resulting in a massive explosion. This would happen because the velocity the penetrating air would fill the vacuum tunnel would be just as great as the velocity of the train and this would lead to increased psi, 2-4 atmospheres.
I have a thought of using a plasma shield to burn up air in front of the train and around the front that could form a bubble of lower pressure around the train allowing for the mag-lev train to travel faster than it can now.
David Cope is correct in his answer; here is additional information:
The Magnaplane--the first and arguably the best Maglev concept--was invented by Prof. Henry Kolm at MIT and Princeton in the 1970's. A scale model was built and tested to demonstrate the concept. The Magnaplane uses superconductors (SC) aboard the train to create an intense magnetic field (~10 teslas). The train runs in a high-conductivity aluminum tube. Below 5 to 20 mph, the train travels on rubber tires. Above 5-20 mph. the SC magnets aboard the train induce sufficient (repulsive) eddy currents in the aluminum beneath the train to levitate the train ~10 cm above the track. Propulsion (acceleration and braking) is accomplished as described by David Cope. The vertical position of the Magnaplane is inherently stable. One preferred option is to operate the Magnaplane in a fully- or partially-evacuated tube. (The concept of using an evacuated tube in a subway system was used in the very first mile of the New York City subway system in the ~1880 or ~1890. See an article in the Smithsonian Magazine.) In the 1980's, I designed and analyzed lateral, vertical, and longitudinal stabilization systems for the Magnaplane system.
The German design uses vertical attraction magnets between lower-field, resistive, electromagnets aboard the train, and an iron rail ~0.5 to 1.0 cm located above the electromagnets. Such a system is inherently unstable, so rapid, powerful feedback circuits aboard the train are required to maintain stability. Furthermore, the iron "rails" must be meticulously positioned so that the train never contacts the rails. This system is used in a high-speed rail system between Hamburg and Berlin, I believe.
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