International Journal of Mechanical Engineering and Technology (IJMET) Volume 9, Issue 5, May 2018, pp. 7–13, Article ID: IJMET_09_05_002 Available online at http://iaeme.com/Home/issue/IJMET?Volume=9&Issue=5 ISSN Print: 0976-6340 and ISSN Online: 0976-6359 © IAEME Publication Scopus Indexed MAGNETIC LEVITATION TRAINS – THE UNFULFILLED PROMISE Sourav Mohanty Research Scholar, School of Management, KIIT University ABSTRACT Magnetic levitation or maglev is a well-established technology. Applications range from advertising displays to the Active Magnetic Bearings used in wind turbines. The technology has however failed to deliver on its promise of high speed trains to revolutionize rail transportation. One maglev line each is operating in Japan, China and Korea, the longest being the 30 km Shanghai line. The ambitious Tokyo Nagoya 286 km line to be completed in 2027 and the feasibility study for a maglev line between Washington DC and Baltimore are the promising new developments. The new Hyperloop transportation concept also uses maglev. The paper outlines the technology used in magnetic levitation trains. The work done in Japan for the Tokyo Nagoya project has established that the basic maglev principles remain valid. New materials have helped make maglev trains lighter and faster. The major drawback for maglev trains has been high costs compared to conventional high speed rail. The ambitious UK Ultraspeed project for an 800 km maglev line connecting London and Glasgow was abandoned in 2007. The Tokyo Nagoya line is under criticism for its cost estimated to be $ 49 billion. Maglev technology needs at least one commercially viable demonstration project such as the Washington DC – Baltimore line to become more widely acceptable. Keywords: Magnetic levitation, Maglev trains, Maglev Cite this Article: Sourav Mohanty, Magnetic Levitation Trains – The Unfulfilled Promise, International Journal of Mechanical Engineering and Technology, 9(5), 2018, pp. 7–13. http://iaeme.com/Home/issue/IJMET?Volume=9&Issue=5 1. INTRODUCTION Magnetic levitation or ‘maglev’ uses magnetic fields to counter gravity to suspend an object in air. Maglev has been widely used in simple applications such as toys and advertising signs. A significant engineering application is in Active Magnetic Bearings which have replaced mechanical bearings, for example in wind turbines to reduce friction. Maglev technology holds the promise of developing magnetic levitation trains that could run at speeds of 500 kmph through elimination of friction between the rails and carriage wheels (Yaghoubi, 2013). This promise has remained unfulfilled in the last 50 years. http://iaeme.com/Home/journal/IJMET 7 [email protected] Sourav Mohanty The world’s first maglev train was a short 600 metre line at the Birmingham airport in UK. This line started in 1984 and was discontinued in 1996. The Berlin M-Bahn was started in 1989 but was discontinued after the unification of the city (Goodall, 2012). Neither country chose to build another maglev line after these first projects. There are only three functional maglev train systems in the world. The 10 km Linimo line in Japan, the 30 km Shanghai Transrapid in China and the 6 km line at the Incheon airport in Korea (Hower, 2016). These operating maglev trains are the demonstration projects that have helped establish the technology. The Tokyo Nagoya 286 km line is under construction indicates a revival of interest in maglev technology. Several proposals have been made for maglev projects in the US. The new Hydroloop transportation system also uses maglev. PROBLEM STATEMENT Maglev technology has not delivered on its promise of transformational change in the field of high speed rail transportation. Maglev projects proposed in several countries have been abandoned in favour of conventional high speed rail projects, primarily due to costs. OBJECTIVES 1. The primary objective of this paper is to review the present status of maglev technology, especially in the context of the new Tokyo Nagoya line. The paper examines the changes in the technology in the 30 years since the first lines were built. 2. The secondary objective is to discuss the problem of high cost that has prevented wider adoption of this technology and to examine if any of the changes in technology promise lower costs. Scope and Relevance In general, in new technologies such as magnetic levitation, continuous research and studies bring about major advancements in functionality and lower costs. This paper examines if maglev technology has seen any substantial advancements in the past 30 years. The Tokyo Nagoya project authorities have done a number of studies to revalidate the technology. A review of the maglev technology being applied to this line will be a good indicator of the progress made in this field. Such a review also helps evaluate if the advances made promise a solution to the problem of high costs that have impeded the growth of maglev train transportation. 2. LITERATURE REVIEW Fundamentals of Maglev Trains The fundamental concept of a magnetic levitation train is shown in Fig-1. The three essential requirements are to lift or levitate the carriage, maintain its horizontal position through lateral guidance and then to propel it forward. These functions are achieved through three sets of metallic loops of aluminum embedded into the concrete guideway (Khan et al, 2017) http://iaeme.com/Home/journal/IJMET 8 [email protected] Magnetic Levitation Trains – The Unfulfilled Promise The first set of metallic hoops is the electromagnet that repels the magnets mounted on the train car and causes it to hover above the guide way. The second set of metallic hoops creates a repulsion magnetic field that keeps the train horizontally stable. The third set of metallic loops is supplied with alternating current and functions as a linear motor. The position of the train above the guideway is continuously monitored through sensors and the current flow through the three sets of coils is regulated to maintain vertical and horizontal stability of the car and the propulsion energy (Khan et al, 2017). Figure 1 Maglev Train Fundamentals (Khan et al, 2017) The Tokyo and Nagoya maglev line uses the same concept as described above. The coils of the superconducting magnets are made of a Niobium-titanium alloy. The coils are cooled with liquid helium to a temperature of -2690C. The propulsion coil on the guideway behaves as a linear motor. Prototype train cars have been built from composite materials and tested to speeds up to 603 kmph. The prototypes have also been evaluated for vibrations and ride quality and suspension dampeners have been introduced (CJR Review, 2017). 3. THE SUSPENSION SYSTEM Three types of suspension systems are used for the magnetic levitation of train carriages as shown in Fig- 2. The Electrodynamic Suspension (EDS) system uses the repulsion force between electromagnets of the same polarity mounted on the train carriage and the guideway. Rubber wheels are fitted to support the maglev train until it reaches the lift-off speed of around 100 kmph (Propel Steps, 2015) Figure 2 Maglev Train Suspension Systems (Propel Steps, 2015) The electromagnets used for levitation are super conducting and are cooled by a cryogenic system mounted on the train car. Passengers need to be shielded from the high intensity magnetic fields. The EDS suspension system has been used in the Japanese Linimo Maglev line and will also be used in the Tokyo Nagoya line (Cassat & Borquin, 2011). In contrast, http://iaeme.com/Home/journal/IJMET 9 [email protected] Sourav Mohanty the Electromagnetic Suspension (EMS) system uses the attraction force between unlike poles of the electromagnets. The train undercarriage wraps around the guideway as shown in Fig 2. These electromagnets do not require cryogenic cooling and passengers do not need to be shielded. A back-up battery fitted in the train car maintains power supply to the levitation electromagnets if there is a power interruption. The EMS system has been used in the Shanghai maglev line (Cassat & Borquin, 2011). The Inductrack is similar to the EDS except that permanent magnets at room temperature are used for levitation. The permanent magnets are made of neodymium-iron-boron alloy and are arranged in a Halbach array. This arrangement increases the magnetic field on one side and reduces the field on the other side to near zero levels. The track consists of metallic loops and induced current in them creates a repulsion magnetic field for levitation. The Inductrack is still to be applied to a working maglev line (Goodall, 2012). Superconducting Magnets Low temperature superconductive coils are used on the Japanese maglev systems, both Linimo and the new Tokyo –Nagoya line, operating at the liquid helium temperature of 4.2 0 K. These coils provide the DC excitation for the propulsion motor and the flux sources for levitation and guidance (Cassat & Borquin, 2011). The Chinese Transrapid system uses high temperature superconducting magnets that operate at 77 0 K which is the liquid nitrogen temperature. This results in a decrease in the mass of the superconducting magnet and lower energy consumption in the on-board cryo-cooler (Cassat & Borquin, 2011). 4. THE MAGLEV TRAIN CAR The cross-section of a typical maglev train car with EDS suspension is shown in Fig 3. The base frame carries the levitation, the guidance and the propulsion coils. A radiation shield is fitted between the base frame and the passenger compartment (Ramireddy, 2012). Figure 3 Maglev Train Car Construction (Ramireddy, 2012) The electromagnets are cooled by two separate cooling systems mounted in the train car, one with liquid helium and the other with liquid nitrogen (Ramireddy, 2012). http://iaeme.com/Home/journal/IJMET 10 [email protected] Magnetic Levitation Trains – The Unfulfilled Promise The Guideway The cross-section of the guideway for the maglev train is shown in Fig 4.