Examination of Levitation of Thin Non-Magnetic Conductor by AC Electoromagnet Type Electro Dynamic Suspension
Because transportation by magnetic levitation has the advantage of not contacting, it has various good points. Conventional studies of electro dynamic suspension (EDS) are aimed on the large-scale applications, and use the non magnetic conductor of 1mm or more in thickness. However, in theoretical, it is possible that the thinner non magnetic conductor of less than 1mm in thickness levitate, using higher frequency or larger magnetomotive force. Therefore, applications to a smaller levitation model can be expected. In this paper, the relation between lift force and the temperature rise in the conductor is examined from the numerical analysis, when we consider a smaller levitation model. Skin effect and electromagnetic force between gaps are taken into account. These results are verified by experiments.
Levitation Characteristics of Magnetically Suspended Vehicles Utilizing Continuous Conductive Sheets
In a magnetically levitated railway system with superconducting vehicular magnetic coil, short-circuiting ground coil, and a loop-type track, the magnetic field produced by ground coils is not uniform and therefore the lift force fluctuates as the train moves and the magnetic flux of the superconducting magnet fluctuates with time. The sheet-type track consists of continuous conductive sheets of aluminum or copper. The levitation characteristics of the sheet-type track have been analyzed so far by directly solving Maxwell's equation or by replacing the sheet current by an image current. In these analyses, it has usually been assumed that the sheet is infinitely or semiinfinitely wide. Until now, the levitation characteristics of a sheet-type track with finite width have been analyzed little. An analysis is given in which a ground sheet with finite width is replaced by a number of conductors with square cross section arranged in the running direction. Self- and mutual inductances of the conductors are taken into account in calculating the levitation characteristics. Calculated levitation characteristics of the sheet-type track are compared with those of the loop-type track.
Forces on Moving Magnets due to Eddy Currents
A magnet or a current‐carrying coil, moving with constant velocity above a conducting plate, will experience magnetic lift and drag forces from the eddy currents induced in the plate. The lift and drag forces are calculated for various coil geometries on the assumption that the conducting plate is thin. For this model, the lift at high speeds approaches the force between the coil and its ``image'' located directly below it, and the drag force falls off as (velocity)−1. The ratio of lift to drag is found to be independent of coil geometry, but the velocity dependence of the lift is greatly affected by the geometry. The ratio of lift to coil weight can be as high as 2000 for a superconducting coil moving at 300 mph at 0.1 m above a conducting plate. The relevance of the calculation to magnetically supported high‐speed vehicles is discussed.