Changes

You may want to start a new blank project for this part of the tutorial lesson. In [[EM.Ferma]], permanent magnets are used as magnetic sources, but they may also be a permeable magnetic material at the same time. Create a permanent magnet source group in the navigation tree. Right-click on the <b>Permanent Magnets</b> item in the navigation tree and select <b>Insert New Permanent Magnet...</b> from the contextual menu. This opens up the New Permanent Magnet dialog. Accept the default name "PM_1 " and the default relative permeability of &mu;_r = 1. Set the values of the components of the magnetization vector as follows:

! scope="col"| Cone Length Ratio! scope="col"| Cone Radius Ratio

Also open the data manager and plot the data file "Sensor_1_Z_HTotal.DAT" in EM.Grid. This plot shows the variation of the magnetic field at the center of the magnets along the Z-axis. At z = 25mm, the magnetic field intensity is 260A275A/m.

In the first part of this tutorial lesson, you simulated a permanent magnet cylinder of height 50mm. In the second part, you simulated two parallel magnet cylinders of height 20mm separated by a spacing of 10mm. The total height of the whole structure is still 50mm. In this part of the tutorial lesson, we are going to treat the spacing between the two cylinders as an air gap and will parameterize its height as a variable called "gap_h". In other words, we will allow the heights of the two cylinders to vary. But we will require the bottom base of "Cyliner_1 " to be fixed at Z = 0 and the top base of "Cylinder_2 " to be fixed at Z = 50mm.

[[Image:Ferma L5 Fig47Ferma_L5_Fig47add.png|thumb|left|550px|The initial variables list showing only the default system variables.]]

Next, you have to associate this variable with the object properties. This requires a little bit of thinking. The height of the two cylinders must be set equal (50mm - gap_h)/2. This makes the total height of your structure h_tot = (50mm - gap_h)/2 + gap_h + (50mm - gap_h)/2 = 50mm, as you want. In [[EM.Cube]], the local coordinate system (LCS) of a cylinder is always set up at the center of its bottom base. As you vary "gap_h", the bottom of "Cylinder_1 " will always stay fixed at Z = 0, while the bottom of "Cylinder_2 " must be located at 50 - (50mm - gap_h)/2 = 25mm + gap_h/2.

Open the property dialog of "Cylinder_1 " and set its height equal to "(50-gap_h)/2". Then, open the property dialog of "Cylinder_2", set its height equal to "(50-gap_h)/2" and set its Z-coordinate to "25+gap_h/2".

Also open the data manager and plot the data file "Sensor_1_Z_HTotal.DAT" in EM.Grid. The figure below shows that at z = 25mm, the magnetic field intensity has increased to 357A/m.

In the previous parts, you assumed that the relative permeability of the permanent magnets was &mu;_r = 1. Alnico is a permanent magnet material with &mu;_r = 3.6. Open the property dialog of the group groups "PM_1" and "PM_2" in the navigation tree and change its relative permittivity to 3.6.

Open the data manager and plot the data file "Sensor_1_Z_HTotal.DAT" in EM.Grid. You can see that along the Z-axis at the center of the two magnets, the field is very much localized and confined to the air gap region and its intensity has increased to a very high value of 634A/m.

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