s setup uses attractiion for levitation and a LIM for propulsion.(Image source: page 27, Linear Motion Electromagnetic Systems.)The setup for the attraction system is very similar to to the setup for the repulsion system, except that the direction of current in one of the coils is reversed, resulting in an attractive force between the coils. Also, the coils are located on an extension of the train that wraps under the track.It is important to notice that as the distance between the two coils decreases, the attractive force increases. Under certain conditions the two coils could get pulled into direct contact, eliminating the air gap between them. This would be very undesirable. Therefore engineers who design attractive levitation system must make use of a secondary system that monitors the air gap distance and can adjust the magnetic field strength appropriately. This secondary system also would make the ride more comfortable for passengers.The magnetic field strength at segment AB due the magnetic field created by segment A'B' isThe force on the lower wire segment AB due the field created by the upper wire segment A'B':The picture below illustrates the direction of FAB, which is the green vector on the drawing labeled FB. FB is perpendicular to ray AB, and the vector B. FB is opposite in direction to Fg , and can balance out the force of gravity.Since there are four straight wires comprising each loop, there are four forces acting on the upper loop.This attractive force provides the lift, or levitating force for the vehicle.Note that the equations are exactly the same, provided that the setups are different. (That is, in the repulsive case, the vehicle coil was above the track coil. In the attractive case presented on this page, the vehicle coil is below the track coil.)Linear Induction MotorsLinear motors are analogous to conventional (rotary) motors. A Linear Induction Motor, or LIM, can be visualized by 'unrolling' a conventional in...
