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Impact of Materials on Reducing Stray Losses (T.E.A.M. Problem 21b)

Transformers with MagNet for SOLIDWORKS

The following benchmark involves two exciting coils directed in opposite directions and shielded by non-magnetic and magnetic steel plates.

Problem 21b involves three different configurations of plates: one magnetic and one non-magnetic plate (referred to in this example as P21b-MN), two magnetic plates (referred to as P21b-2M), and two non-magnetic plates (referred to as P21b-2N). The flux density is measured along contours on the plates' surface and compared with measured results.

The purpose is to investigate the effects of shielding on flux densities outside of transformers. Shielding can be used to substantially reduce magnetic field strengths outside of a transformer, but the electric properties of the material can have a great impact on how the shielding affects the field strengths. Considerations must be taken to determine the type of shielding required for each individual application.

Presented here is an example based on the Testing Electromagnetic Analysis Methods (T.E.A.M.) problem #21b: 3-D Stray Field Loss. The benchmark can be found on the International Compumag Society's website.

Transformer magnetic shielding plates

METHODS and RESULTS

MAGNETIC FLUX DENSITY in the SHIELDING PLATES

To simulate TEAM Problem 21b, an AC Time Harmonic study was created in MagNet for SOLIDWORKS. The source current was modeled with sinusoidal input. Displayed here are the magnetic flux density plots for all three configurations of the steel plates. The two images on the left-hand side are for the case of one magnetic and one non-magnetic steel plate (P21b-MN).

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MAGNETIC FIELD DIRECTION

MagNet for SOLIDWORKS' can be used to produce plots that show both the magnitude and direction of magnetic fields. Shown here is a plot of the magnetic (B field) for the configuration P21b-MN. The plate on the left is the magnetic plate, and the plate on the right is the non-magnetic plate.

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OHMIC LOSS in the SHIELDING PLATES

Displayed here is a plot of the ohmic loss in the steel plates for each of the three configurations. The two images on the left-hand side are both for P21-MN.

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INDUCED CURRENT DENSITY and DIRECTION

Current density (J field) inside the plates for each of the three configurations. The eddy currents induced by the changing magnetic field can be seen clearly with this view. The two images on the left-hand side are both for P21-MN.

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COMPARING MAGNET for SOLIDWORKS & MEASURED RESULTS

The description of TEAM Problem 21b presents experimental data measuring the magnetic flux densities along contours off of the surface of the magnetic and non-magnetic steel plate in configuration P21b-MN. Shown here is a graphical comparison between the results that were generated by MagNet for SOLIDWORKS simulation and the experimental data.

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