Arbitrary Motion due to rotating magnets

Infolytica's MagNet software allows for arbitrary motion in both its 2-dimensional and 3-dimensional Transient with Motion solvers. Any number of combinations of translational and rotational degrees of freedom is allowed within one simulation.

With such a wide range of definitions of motion possible, the results can be very interesting, as shown in this gallery page. Presented here is a two-pole rotating drum consisting of two pairs of magnets with opposing radial magnetization directions. The drum is free to rotate, as well as move freely in the plane of rotation, influenced only by magnetic and gravitational forces. In the first simulation, the device is placed within a copper pipe, while in the second simulation, the device is placed above a copper ramp. Repelling forces, brought about by induced currents in the copper due to the rotating magnetic field, oppose the gravitational forces, thereby causing the device to levitate. The rotating drum is running at fixed angular velocity but motion in the x and y directions are unconstrained.

The rotational device inside of the copper pipe can be easily modified to represent the modeling of a magnetic bearing inside of its casing.

Results

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On the right is the two-pole rotating drum, shown in its initial position above the copper ramp that is used in the second simulation.

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The magnetic flux density field arrow and shaded plots are presented on the right after running a 2-dimensional static solution of the four magnets. The plot demonstrates the two pairs of radial magnetization directions used in both simulations.

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When the drum begins to rotate, the rotating magnetic fields from the four magnets induce currents inside of the copper. The image here is of a contour plot of the flux function and a shaded plot of the current density field at an intermediate time instant.

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The two graphs on the right are of the position of the center of gravity of the drum inside of the copper pipe and on top of the copper ramp. Both simulations stop when contact is made with copper, which in these 2 cases are the blue lines drawn on the graphs located a half drum diameter away from the copper surface (black line).

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Shown on the right are graphs of force as a function of time of the two simulations. Paired up with the two previous graphs, it can be seen that the induced currents, and hence the forces, greatly increase when the magnets approach the copper causing it to repel the drum.