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.
Influence of electric fields on friction electrification between metals and borosilicate glass
Abstract In a cylindrical geometry, electric fields were applied through the entire contact area between the sliding metal and the glass surface. The maximum electric charges developed on the metal were measured and plotted against the applied voltage producing the field. The metals were high-purity nickel and gold. The borosilicate glass was Pyrex, brand 7740. The experiments with nickel, which has a work function greater than that of the glass, were performed in 10 −7 mm Hg vacuum. The experiments with gold, with a work function smaller than that of glass, were carried out in air at atmospheric pressure. The results show that: 1. 1) There is both asymmetry and a reversed slope portion in the charge vs. voltage plot. 2. 2) For a certain range of reversing fields, the electric charge developed on the nickel is always negative and the charge on gold is always positive.