Analysis of speed characteristics of attracting magnet for magnetic levitation of vehicles

Theoretical analysis was made of the magnetic field in the air gap between the attracting magnet and the rail for the electromagnetic levitation of vehicles. Eddy current induced by the magnetic field in the rail weakens the field, particularly near the leading end of the magnet, and decreases the attracting force as the magnet speed becomes higher. Eddy current also generates drag. Analytical solutions of the field equations were derived and formulas for calculating forces were obtained. Magnetic field distribution within the air gap was calculated to show how the excited field is weakened by the eddy current in the rail. Speed characteristics of the magnet, such as attracting force versus speed curves, drag versus speed curves, lift/drag ratio versus speed curves, were calculated, and are compared with some experimental curves. These curves show that speed-characteristics of the attracting magnet can be very superior in a very wide speed range, if it is designed properly. It is shown how parameters, such as magnet length, rail thickness, etc., affect the speed characteristics of the magnet.