TEAM Benchmark Family: Problem 21b Field Loss in Power Transformer

Shielding can be used to substantially reduce magnetic field strengths outside of a transformer. Considerations are needed to determine the type of shielding required; its electric properties and geometry.

The International Compumag Society has put forth a set of problems designed for Testing Electromagnetic Analysis Methods (T.E.A.M.). Within this group is a benchmark problem for calculating loss in a shielding plate, 3-D Stray Field Loss Model: Benchmark Family.

Presented here is MagNet's analysis of the third set of configurations from the family of benchmarks involving two exciting coils directed in opposite directions and shielded by a pair of conducting steel plates. The shield has three configurations; one magnetic and one non-magnetic conducting plate (MN), two magnetic conducting plates (2M) and two non-magnetic conducting plates (2N). The nonlinear eddy current and hysteresis losses are compared in both configurations to measured results. By taking advantage of symmetry present in the geometry, only a quarter model is used in configurations 2M and 2N and a half model for configuration MN. These simplifications decrease the time required to complete the simulation.


Results

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Since the sources powering the transformer are sinusoidal, MagNet's Time Harmonic 3D solver can be used to simulate this model. Shown on the right are snapshots of the magnetic flux density plots on all three steel plate configurations. The first two images are for sub-model MN with different extents on their shaded plot legends, this is done on order to see the field in the magnetic and non-magnetic plates.

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The integral of the ohmic loss and iron loss fields in MagNet are used to compare to the measured eddy current-hysteresis model of TEAM Problem 21b. Shown on the right is a graphical comparison of power losses for the three steel plate configurations.

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In addition to measured power loss values, TEAM Problem 21b also presents measured magnetic flux densities along contours off of the surface of the steel plate for the configuration involving a magnetic and a non-magnetic plate. Shown on the right is a graphical comparison between MagNet and the measured results along a contour just above and just below the plates.