with a hole (TEAM 7)

The model consists of a thick aluminum plate with an eccentric hole and an exciting coil. The entire structure will be modeled since it is asymmetrical. The model is shown below.

Skin Depth Calculation

The first step is always to calculate the skin depth (d) or the depth of penetration of the field for the conducting regions. For the current problem, the skin depth must be calculated in the Aluminum plate at a frequency f = 50 Hz, m = mo = 4p X10-7 H/m and s = 3.526 X 107 S/m. Using the following equation,

we obtain d = 11.98 mm. Since the height of the Aluminum plate H = 19mm, thus H/d = 19/11.98 = 1.58. Hence the current problem indeed requires the AC Magnetic analysis. Furthermore, as mentioned earlier, for the AC magnetic analysis, the mesh must have at least two elements per skin depth in the conducting regions where an eddy current is expected to be induced. Given a ratio of H/d = 1.58, 3 to 4 mesh elements along the height of the Aluminum plate are sufficient.

Since the coil is stranded, it does not support eddy currents. Thus, the calculation of the skin depth in the coil is not needed.

EMS Results

• Real Part of the Magnetic Flux Density in the Plate at wt=0

  

• 
  Real Part of the Magnetic Flux Density in the Plate at wt=90

  

• Real Part of the Eddy Current Density in the Plate at wt = 0

  

• The Dissipated Power Results