Magnetic levitation (maglev) is a highly advanced technology which provides, through magnetic forces, contactless movement with no wear and friction and, hence, improved efficiency, followed by reduced operational costs. It can be used in many fields, from wind turbines to nuclear energy and elevators, among others. Maglev trains, which use magnetic levitation, guidance and propulsion systems, with no wheels, axles and transmission, are one of the most important application of the maglev concept, and represents the first fundamental innovation of rail technology since the launch of the railroad era. Due to its functional features, which replaces mechanical components by a wear free concept, maglev is able to overcome some of the technical restrictions of steel-wheel on rail (SWR) technology, running smoother and somewhat quieter than wheeled systems, with the potential for higher speeds, acceleration & braking rates and unaffected by weather, which ultimately makes it attractive for both high speed intercity and low speed urban transport applications. From a technical perspective, maglev transport might rely on basically 3 technological concepts: i) electromanetic suspension (EMS), based on the attraction effect of electromagnets on the vehicle body, that are attracted to the iron reactive rails (with small gaps and an unstable process that requires a refined control system); ii) Electrodynamic Levitation (EDL), which levitates the train with repulsive forces generated from the induced currents, resulted from the temporal variation of a magnetic field in the conductive guide ways and iii) Superconducting Levitation (SML), based on the so called Meissner Effect of superconductor materials. Each of these technologies present distinct maturity and specific technical features, in terms of complexity, performance and costs, and the one that best fits will depend on the required operational features of a maglev system (mainly speed). A short distance maglev shuttle first operated commercially for 11 years (1984 to 1995) connecting Birmingham (UK) airport to the the city train station. Then, high-speed full size prototype maglev systems have been demonstrated in Japan (EDL) (552 kph - 343 mph), and Germany (EMS) (450 kph - 280 mph). In 2004, China has launched a commercial high speed service (based on the German EMS technology), connecting the Pudong International Airport to the outskirts of the city of Shanghai. Japan has launched a low speed (up to 100 kph - 62.5 mph) commercial urban EMS maglev service (LIMINO, in 2005), followed by Korea (Incheon, in 2016) and China (Changsha, in 2016). Moreover, Japan is working on the high speed Maglev concept, with the so called Chuo Shinkansen Project, to connect Tokio to Nagoya, in 2027, with top speeds of 500 kph (310 mph). China is also working on a high speed maglev concept (600 kph - 375 mph), supported on EMS Maglev technology. Urban Maglev concept seeks to link large cities, with their satellite towns and suburbs, to downtown areas, as a substitute for subways, due to its low cost potential, compared to metros and light rail (basically due to their lower turning radius, grade ability and energy efficiency). High Speed Maglev is also seen as a promising technology, with the potential do provide high quality passenger transport service between cities in the 240–1,000 km (150–625 mi) distance range into a sustainable and reliable way. This work is supposed to present, based on a compilation of a multitude of accredited and acknowledged technical sources, a review of the maglev transport technology, emphasizing its potential and risks of the low and high speed (urban and intercity) market, followed by a brief summary of some case studies.
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