TEAM Benchmark Family: Problem 21^a 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 second set of configurations from the family of benchmarks involving two exciting coils directed in opposite directions and shielded by a non-magnetic steel plate. The steel plate has four configurations; no slot, one slot, two slots and three slots. The eddy current losses are compared in all configurations to measured results. By taking advantage of symmetry present in the geometry, only a quarter of the model can be modelled which decreases 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 shaded current density plots of the induced eddy currents in the four steel plate configurations.

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Along with shaded current density plots MagNet's post-processor also automatically computes ohmic loss fields. Shown on the right are snapshots of the shaded ohmic loss field plot for the four steel plate configurations.

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The integral of the ohmic loss field in MagNet is used to compare to the measured eddy current model of TEAM Problem 21^a. Shown on the right is a graphical comparison of power losses for the four steel plate configurations.

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In addition to measured power loss values, TEAM Problem 21^a also presents measured magnetic flux densities along contours off of the surface of the steel plate for configuration 21^a-2. Shown on the right is a graphical comparison between MagNet and the measured results along the two contours.

Simulation characteristics for all four models.

Sub-model: P21a-0	Sub-model: P21a-1
CPU: AMD AthlonTM 64 X2 Dual 2.41 GHz.	CPU: AMD AthlonTM 64 X2 Dual 2.41 GHz.
Peak RAM used: 673 MB.	Peak RAM used: 688 MB.
Number of degrees of freedom: 358,401.	Number of degrees of freedom: 365,937.
Number of tetrahedra: 520,797.	Number of tetrahedra: 521,283.
Solve time: 5 minutes 36 seconds.	Solve time: 5 minutes 53 seconds.
Sub-model: P21a-2	Sub-model: P21a-3
CPU: AMD AthlonTM 64 X2 Dual 2.41 GHz.	CPU: AMD AthlonTM 64 X2 Dual 2.41 GHz.
Peak RAM used: 571 MB.	Peak RAM used: 621 MB.
Number of degrees of freedom: 352,277.	Number of degrees of freedom: 366,022.
Number of tetrahedra: 562,748.	Number of tetrahedra: 528,300.
Solve time: 5 minutes 09 seconds.	Solve time: 6 minutes 15 seconds.