e. Combining the reliability and speed advantages, this looks to be a promising possibility. Low Wear and MaintenanceBecause lift and guidance forces are distributed over a large area, contact stresses are at a minima. The Linear Motor allows noncontact propulsion and braking, in contrast to conventional rail where severe stresses occur from wheel/rail contact and by power transfer. A low cost maintenance program is a certain advantage associated with this technology. Important IssuesDrag Forces: Magnetic and AerodynamicWhen a conductor moves through a magnetic field, the changing flux induces electric currents as reviewed in the induction page of the Basic Physics section.These eddy currents then react with the magnetic field in such a way as to brake motion through the field. Due to of this phenomenon, a part of the propulsion energy is spent counteracting the drag force. As the table from Linear Motion Magnetic Systems shows, the drag force increases as the speed increases, for the most part. As a maglev gains speed, it requires more and more energy just to remain at cruising speed.In addition to the magnetic drag force, conventional aerodynamic drag is present. Although both forms of drag are undesirable in many ways, there are some ways of utlizing them to our advantage. The drag forces can help brake a maglev train quite efficiently. In the introduction, there is a photograph of a Maglev train with aerodynamic brakes extended.The DisadvantagesTechnical Problems - A Study in the Feasibility of the SCM The major technical barrier to the mass adoption of Maglev as a new transportation system lies in problems with the superconducting magnets (hereafter SCM) used to levitate and power the trains.To date most Maglev trains have utilized an SCM made of NbTi. The SCM develops extremely high temperatures during operation, during which it must be cooled down to four degrees Kelvin to maintain its properties. Liquid helium is usually used fo...
