Lecture on Maglev Technology

Introduction

• Location: Japanese mountain pass
• Feature: 43-kilometer-long magnetic levitation train track
• Aim: Connect Tokyo and Osaka with the world’s first inter-city Maglev train

Functionality of Maglev Trains

• Use superconducting magnets
  • Trains hover 10 cm above the track
  • Speed: 500 km/h
  • No physical contact with the track
  • Can operate in any weather, lower maintenance costs

Current and Future Maglev Usage

• Current: Only one commercial high-speed Maglev line (30 km, Shanghai Airport to city)
  • Short track defeats high-speed advantage
  • Average speed: 225 km/h
• Planned network: 400 km (longer-term goal)
• Comparison: 60,000 km of regular high-speed tracks globally
• Challenges and reasons for limited deployment

Working Principle of Maglev Trains

• Two primary levitation methods
  • Attractive Forces: Combines magnetic iron rail and electromagnet (active system)
    • Example: Shanghai Maglev line (8-12 mm gap)
  • Repulsive Forces: Uses onboard magnets and passive coils on track (Japan’s choice)
    • Gap: 10 cm for stability in earthquake-prone regions
    • Dynamic system: Works only when the train is fast
• Magnet Arrangement
  • North and South poles arranged vertically on sides of the track
  • Figure 8 pattern for magnetic coils

Superconducting Technology

• SCmaglev trains uses superconducting coils for stability
  • Niobium-titanium coils cooled using liquid helium and nitrogen
  • Uses Pulse Tube Refrigerators for cooling, similar to technology in James Webb telescope

Addressing Magnetic Field Concerns

• Magnetic field redirection using electric steel shielding
  • Electric steel contains 3% silicon, post-processed for large crystal grains
  • Additional design trick by flipping magnet poles for low-field bubble in cabin corridors
• Field strength reduced to 0.5 mT
• Construction materials: Low-magnetic steel or fiber-reinforced composites

Propulsion and Braking

• Propulsion using a linear motor (no physical contact)
  • Alternating coils attract and repel train
  • Regenerative braking for slowing
• Low-speed braking: Wheel-based, air brake at high speeds
• Power supply at high speeds via linear induction coil, no third rail

Economic and Operational Challenges

• Cost comparison: High-speed rail vs. Maglev
  • Maglev: 10-50 times more expensive
  • Example: Tokyo-Nagoya Maglev: $77 million/km
• Long-distance economic viability (e.g., Tokyo-Nagoya)
• Tunneling increases costs and operational expenses
• Energy usage: 30% higher than existing lines, but better than flying

Conclusion

• Maglev offers speed and efficiency but faces economic and logistical challenges
• Practical usage likely limited to special projects
• Future possibilities with room temperature superconductors

Further Learning

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