Why Do Maglev Trains Need to Float

Magnetic Levitation (Maglev) trains are famous for their high speed, but how can such heavy trains float? And why do they need to float at all?

Operating Principle

A maglev train is a high-speed transport system that uses magnetic forces to suspend the train above the track. It does not rely on wheels touching rails; instead, electromagnetic attraction or repulsion lifts the train and keeps it hovering above the guideway. Propulsion is provided by linear motors, with the track itself acting like a long motor that directly drives the train forward.

Currently, maglev trains are mainly divided into two types: Electromagnetic Suspension (EMS) and Electrodynamic Suspension (EDS), which can be described as attraction-based and repulsion-based systems respectively.

Electromagnetic Suspension (EMS) relies on the attractive force of electromagnets to hold the train just above the track. Powerful electromagnets are mounted beneath the train, while the guideway is lined with ferromagnetic plates. When the magnets are energized, they pull the train toward the track. Although it looks as if the train is sticking to the guideway, precise computer control keeps it hovering at a gap of about 8–10 millimeters.

If the train gets too close, the system reduces current to weaken the pull; if it drifts too far, the current is increased to strengthen it. This constant adjustment allows the train to remain stably suspended without touching the track. Because EMS is inherently unstable, it requires continuous electronic control, but its advantage is that the train can remain levitated even when stationary, without needing wheels for support.

Electrodynamic Suspension (EDS), on the other hand, uses the repulsive effect between magnets and conductors to support the train. Superconducting magnets are installed on the train, and as it moves, they induce currents in coils embedded in the guideway. According to Lenz’s law, these coils generate opposing magnetic fields, creating repulsive forces that lift the train. The levitation gap is much larger than EMS, typically 50–100 millimeters.

EDS is highly stable at high speeds because the repulsive force increases with velocity, allowing the train to remain suspended naturally without constant fine-tuning. However, at low speeds or when stationary, the repulsion is too weak to support the train, so wheels are needed until sufficient speed is reached for full levitation.

Electromagnetic Suspension and Electrodynamic Suspension

Advantages and Limitations

The reason maglev trains must float is to eliminate friction between wheels and rails. In conventional rail systems, steel wheels press against steel tracks, and as speed rises, friction and vibration increase, limiting maximum speed and creating wear and safety risks. By levitating above the track, maglev trains remove this contact entirely, breaking through the limits imposed by wheel-rail friction.

Advantages of levitation include:

• High-speed operation
  • With no friction, resistance is reduced to air drag alone, allowing much higher speeds
  • In theory, maglev can exceed 600 km/h, faster than conventional high-speed rail
• Smooth and comfortable ride
  • The absence of wheel vibration makes travel quieter and more stable
  • Ideal for long-distance journeys.
• Lower track and wheel wear
  • Since there is no physical contact, both track and train components last longer
  • Reducing repair frequency
• Improved safety
  • At high speeds, there is no risk of instability from friction or wear
  • Track design can be more flexible with curves and gradients.

Despite these advantages, maglev trains are extremely expensive to build. They require specially designed guideways with embedded coils and magnetic materials, constructed with very high precision. This means the cost per kilometer is often double or more compared to high-speed rail. Moreover, maglev systems cannot share existing rail infrastructure, so new stations, control centers, and entire networks must be built, further raising investment.

Maintenance is also demanding. While maglev avoids wheel and rail wear, its electromagnetic systems, superconducting magnets, and cooling equipment require constant specialized upkeep. Superconducting technology in particular must be kept at very low temperatures, consuming energy and adding cost. As a result, maintenance shifts from mechanical wear to advanced technological systems, and overall expenses are not lower than high-speed rail.

Global Situation

Maglev trains clearly offer superior speed and comfort, but their high construction and maintenance costs have limited widespread adoption. Today, they remain largely in demonstration use. Shanghai’s maglev line and Japan’s ongoing Chūō Shinkansen project are notable examples, yet large-scale global deployment is still far off.

Current adoption status:

• China: Only the Shanghai line between Pudong Airport and the city center is in commercial operation, running at 430 km/h. A new 600 km/h maglev system is under development but still in testing.
• Japan: JR Central is building the Chūō Shinkansen maglev between Tokyo and Nagoya, planned for 500 km/h, but costs are enormous and construction lengthy.
• Germany: Developed the Transrapid system, but high costs and political factors prevented large-scale rollout.
• Worldwide: Maglev technology has existed for decades, but only a handful of demonstration lines operate today, far less common than high-speed rail.