The bearings developed at Livermore employed cylindrical magnet arrays to sta INDUCTRACK MAGLEV SYSTEM could allow trains to glide across the country. Apr 3, High reliability and lower maintenance and operating costs make magnetic levitation (maglev) technology integral to advancing the nation’s. May 9, By contrast, maglev requires complex and expensive infrastructure Called the Inductrack, the new system is passive in that it uses no.

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FOR the past two decades, prototype magnetically levitated maglev trains cruising at up to kilometers per hour have pointed the way to the ijductrack in rail transport. Their compelling advantages include high speeds, little friction except aerodynamic drag, low energy consumption, and negligible air and noise pollution. However, maglev trains also pose significant drawbacks in maintenance costs, mechanical and electronic complexity, and operational stability.

Some maglev train cars, for example, employ superconducting coils to generate their magnetic field. These coils require expensive, cryogenic cooling systems.

These maglev systems also require complicated feedback circuits to prevent disastrous instabilities in their high-speed operation. Lawrence Livermore scientists have recently developed a new approach to magnetically levitating high-speed trains that is fundamentally much simpler in design and operation requiring no superconducting coils or stability control circuitspotentially much less expensive, and more widely adaptable than other maglev systems.

The new technology, called Inductrack, employs special arrays of permanent magnets that induce strong repulsive currents in a “track” made inductrsck of coils, pushing up on the cars and levitating them. Totally Passive Technology During the past two years, a Livermore team, indutcrack by physicist Richard Post, has successfully demonstrated the Inductrack concept in test trials. The test runs demonstrated the system’s totally passive nature, meaning that achieving levitation requires no control currents to maintain stability, and no externally supplied currents inducctrack in the tracks.

The Inductrack: A Home-Grown Maglev System for our Nation

Instead, only the motion of train inductack above the track is needed to achieve stable levitation. The results have been so promising that NASA has awarded a three-year contract to the team to explore the concept as a way to more efficiently launch satellites into orbit.

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Inductrack involves two main components: The permanent magnets are arranged in configurations called Halbach arrays, mgalev after Klaus Halbach, retired Lawrence Berkeley National Laboratory physicist.

Originally conceived for particle accelerators, Halbach arrays concentrate the magnetic field on one side, while canceling it on the opposite side.

When mounted on the bottom of a rail car, the arrays generate a magnetic field that induces currents in the track coils below the moving car, lifting the car by several centimeters and stably centering it. When the train car is at rest in a stationno levitation occurs, and the car is supported by auxiliary wheels. However, as soon as the train exceeds a transitional speed of 1 to 2 kilometers an hour a slow walking speedwhich is achieved by means of a low-energy auxiliary power source, the arrays induce sufficient currents in the track’s inductive coils to levitate the train.

To test the Inductrack concept, Post, project engineer J. Ray Smith, and mechanical technician Bill Kent assembled a one-twentieth-scale model of linear track 20 meters long Figure 1. The track contained some 1, rectangular inductive wire coils, each about 15 centimeters wide.

Each coil was shorted at its ends to form a closed circuit but not otherwise connected to any electrical source.

Along the sides of the track, they attached aluminum rails on which a kilogram test cart could ride until the levitation transition velocity was exceeded Figure 2. Finally, the team secured Halbach arrays of permanent magnet bars to the test cart’s underside for levitation and on the cart’s sides for lateral stability. The cart was then launched mechanically at the beginning of the track at speeds exceeding 10 meters per second.

High-speed still and video cameras revealed that the cart was consistently stable while levitated, flying over nearly the entire track length before settling to rest on its wheels near the end of the track. Post says the test results are maglfv with a complete theoretical analysis of the Inductrakc concept he performed with Livermore physicist Dmitri Ryutov.

The theory predicts levitation forces of up to 50 metric tons per square meter of magnet array using modern permanent magnet materials such as neodymium-iron-boron. The theory also shows levitation of loads approaching 50 times the weight of the magnets, important for reducing the cost relative to maglev vehicles. External Power Needed Post notes that a power source is needed to accelerate the cart to its operating speed of 10 to 12 meters per second.


The first section of the test track uses a set of electrically energized track coils–aided by a stretched bungee cord–to reach this speed.

A full-scale train might use an electronic drive system, as found on experimental German trains, or even a jet turbine, as proposed by Inductrack engineer Smith. Even though the electromagnetic drag associated with Inductrack becomes small at high speeds, indductrack auxiliary power source would also be needed to maintain the train’s high speed against aerodynamic drag.

The amount of power needed depends on the weight of the vehicle and its maximum speed. If the external drive power ever fails, or when the train arrives at a station, the train cars would simply coast to a stop, easing down on their auxiliary wheels. In this sense, Inductrack is a true fail-safe system.

Livermore is one of the few institutions to explore the uses of the Halbach array. The Livermore battery uses inductraco Halbach arrays both to generate power and to achieve nearly frictionless magnetic bearings that minimize the loss of stored energy. The Halbach array offers other benefits besides levitation.

S&TR | November Maglev on the Development Track for Urban Transportation

Because its magnetic fields cancel out above the magnets, there is no worry about magnetic fields affecting passengers’ iinductrack pacemakers. In contrast, passengers must be magnetically shielded on maglev trains employing superconducting coils.

The study found that while an Inductrack system would cost more to build than conventional rail systems, it should be less expensive than maglev trains using superconducting coils. The study also found that Inductrack should be able to achieve speeds of kilometers per hour and up and demonstrate lower energy costs, wheel and rail wear, propulsion maintenance, and noise levels.