Power Transformer under Short-circuit condition
The model is a three phase shell type 50kVA 20kV/380V distribution transformer. This transformer is of the Wescor type and includes four core sections and three pairs of windings corresponding to the three phases.
Results
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Due to its symmetrical geometry, one quarter of the full model can be modeled as shown in the right side figure. A field normal boundary condition and a flux tangential boundary condition are set on the appropriate symmetry planes.
The primary voltages for phase A, B and C are (2887 Vrms,0 degrees), (2887 Vrms, 120 degrees), and (2887 Vrms, 240 degrees), respectively. The secondary windings are short-circuited. The number of turns of each primary winding is 1632, and the number of turns of each secondary winding is 54.
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This figure shows the solution mesh generated by MagNet. The mesh contains 470,900 tetrahedra and 83,160 nodes. The Time-Harmonic 3D is used. The polynomial order is set to 3 for coils and 2 for other components; and the maximum element sizes are set to 10 mm for the cores and 7 mm for the windings. MagNet's mesh controls allows these settings to be easily applied and an appropriate mesh generated.
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This figure shows the shaded plot of the flux density (|B| at 0 degrees) on the field normal symmetry plane.
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This figure shows the distribution of |B| at 0 degrees along the line from point A to point A'(shown in the above figure), which is situated in the air gap between the primary and the secondary windings of Phase C.
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This figure shows the arrow plot of B at 0 degrees on the flux tangential symmetry plane.
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This figure shows the shaded plot for the JxB force density (N/m
3) on the windings of Phase C.
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The two figures on the right illustrate the distributions of JxB Lorentz force density of the force along a horizontal cut through the central plane (shown in the above figure) on the filaments of the primary winding of Phase C.
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Global quantities are reported in the post-processing bar. The right side figure shows the current (I) values for each winding. The impedance of each winding can be easily calculated by the equation
Z=V/I.
For example, the impedance Z¡¯ of primary winding #1 (phase A) for this one quarter model is (17.8467 + j92.17836) ohm; the impedance Z of this winding for the whole transformer is 4xZ¡¯, which is (71.3868 + j368.71344) ohm.
The model is a three phase shell type 50kVA 20kV/380V distribution transformer. This transformer is of the Wescor type and includes four core sections and three pairs of windings corresponding to the three phases.
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