Magnetic Drag Force due to Iron Losses in Magnetic Rail of Magnetically Levitated Train.

Abstract

Large eddy current is induced at high speed in a slub type rail of a electromagnetically levitated train. The eddy current causes magnetic drag force and decreases attracting force between the magnet and the rail.In this paper, magnetic drag force in a system, which has magnetic rails made of laminated iron sheets, was studied theoretically and experimentally, and the following results were obtained:(1) Magnetic drag force in a system with a laminated iron rail was measured using a rotary disc type apparatus. Calculated values were simulated with 2-dimensional finite element method. The calculated values of magnetic drag force were approximately equal to the measured values, and the difference between the calculated and the measured values was within 10%. This result shows that the theory is reasonable.(2) The ratio of magnetic drag force to magnetic attracting force of a slub type rail is about a few %. It was confirmed that the ratio of a laminated rail in this paper was less than 0.3% and that adoption of laminated rails is effective.(3) The magnetic flux density in the air gap between the magnet and the laminated iron rail does not decrease at high speed of 170km/h. This indicates that the attracting force is constant even at high speed and therefore stable levitation charcteristics will be obtained.