TRANSFORMER ARRANGEMENT

Abstract

The disclosure relates to a transformer arrangement comprising a transformer which comprises at least one phase winding. The phase winding has coil turns around a coil axis. The transformer arrangement further comprises a transformer tank having walls forming an enclosure in which the transformer is arranged. The enclosure contains an incompressible medium in which the transformer is immersed. A screen is arranged in the transformer tank, between the walls of the transformer tank and the at least one phase winding of the transformer. The screen has an inner, transformer-facing, surface and an outer, wall-facing, surface. The screen is further arranged distanced from the at least one phase winding. The transformer has lateral sides parallel with the coil axis. The screen has at least one lateral part aligned with the lateral sides of the transformer, and wherein the at least one lateral part of the screen circumscribes the transformer.

Claims

1. A transformer arrangement comprising: a transformer comprising at least one phase winding, said phase winding having coil turns around a coil axis, the transformer having a first extension along a first axis parallel with the coil axis, a second extension along a second axis and a third extension along a third axis, said first, second and third axes being perpendicular to each other, and wherein the transformer has lateral sides parallel with the coil axis; a transformer tank having walls forming an enclosure in which said transformer is arranged, said enclosure containing an incompressible medium in which the transformer is immersed; and a screen arranged in said transformer tank, between the walls of the transformer tank and the at least one phase winding of the transformer, said screen having an inner, transformer-facing, surface and an outer, wall-facing, surface, wherein the screen is arranged distanced from the at least one phase winding of the transformer, in that the screen has at least one lateral part aligned with the lateral sides of the transformer, the at least one lateral part of the screen comprising a continuous band that circumscribes the transformer.

2. The transformer arrangement according to claim 1, wherein the at least one lateral part of the screen has a height along the first axis being equal to, or less, than a height of the at least one phase winding.

3. The transformer arrangement according to claim 1, wherein the screen is configured to be free from structural resonances at twice a network frequency by being rigid, by comprising a volumetrically compressible lining, or by comprising a granular material.

4. The transformer arrangement according to claim 1, wherein the inner surface of the screen comprises a volumetrically compressible lining.

5. The transformer arrangement according to claim 4, wherein the lining has a bulk modulus 1.7 GPa.

6. The transformer arrangement according to claim 1, wherein the screen comprises a granular material.

7. The transformer arrangement according to claim 6, wherein the granular material has a density of more than 870 kg/m.sup.3, or more preferably a density of more than 1600 kg/m.sup.3.

8. The transformer arrangement according to claim 6, wherein the screen is arranged on the walls of said transformer tank.

9. The transformer arrangement according to claim 1, wherein the screen is arranged distanced from the walls of the transformer tank.

10. The transformer arrangement according to claim 9, wherein, in any point of the screen, a distance between said point of the screen and a closest part of the at least one phase winding of the transformer is less than a distance between said point of the screen and a closest part of the walls of the transformer tank.

11. The transformer arrangement according to claim 1, wherein the transformer has a first end along the first axis and an opposite second end along the first axis, and wherein the transformer tank has a first wall extending transversely to the first axis adjacent to the first end of the transformer and an opposite second wall extending transversely to the first axis, adjacent to the second end of the transformer, and wherein the screen has at least one first part extending transversely to the first axis and wherein the at least one first part is arranged between the first end of the transformer and the first wall of the transformer tank.

12. The transformer arrangement according to claim 11, wherein the screen further comprises at least one second part extending transversely to the first axis and wherein the at least one second part is arranged between the second end of the transformer and the second wall of the transformer tank.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Further objects and advantages of, and features of the disclosure will be apparent from the following description of one or more embodiments, with reference to the appended drawings, where:

[0039] FIG. 1 shows a perspective view of an exemplary embodiment of the present disclosure.

[0040] FIG. 2 shows a perspective view of an exemplary embodiment of the present disclosure.

[0041] FIG. 3 shows a perspective view of an exemplary embodiment of the present disclosure.

[0042] FIG. 4 shows a perspective view of a screen according to an exemplary embodiment of the present disclosure.

[0043] FIG. 5 shows a perspective view of an exemplary embodiment of the present disclosure.

[0044] FIG. 6 shows a top-down view of a screen according to an exemplary embodiment of the present disclosure.

[0045] FIG. 7 shows a perspective detail of a screen according to an exemplary embodiment of the present disclosure.

[0046] FIG. 8 shows simulated results of an exemplary embodiment of the present disclosure.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

[0047] The present disclosure is developed in more detail below referring to the appended drawings which show examples of embodiments. The disclosure should not be viewed as limited to the described examples of embodiments. Like numbers refer to like elements throughout the description.

[0048] FIG. 1 illustrates a transformer arrangement 100 comprising a transformer 10, which comprises at least one phase winding 12. The illustrated transformer 10 has three phase windings 12. The phase winding 12 has coil turns around a coil axis c. The transformer arrangement 100 further comprises a transformer tank 20 having walls 22 forming an enclosure in which said transformer 10 is arranged. In the illustrated example, the transformer tank 20 is displayed open to the viewer to expose the transformer 10 inside. In practice, the transformer tank is obviously closed on all sides. The enclosure contains an incompressible medium in which the transformer 10 is immersed. A screen 30 is arranged in the transformer tank 20, between the walls 22 of the transformer tank 20 and the at least one phase winding 12 of the transformer 10. The screen 30 has an inner, transformer-facing, surface and an outer, wall-facing, surface. The screen 30 is arranged distanced from the at least one phase winding 12 of the transformer 10. In other words, the screen is not in direct mechanical contact with any phase winding 12 of the transformer 10. Thereby, the screen is separated from direct structural vibrations of the of the at least one phase winding, which vibrations are generated during operation of the transformer. The screen 30 is configured to block inertia-forces of the incompressible medium emanating from the phase winding 12 such that vibrations of the incompressible medium are reduced at the tank walls 22. Consequently, displacement of the tank walls 22, due to movement of the incompressible medium, will also be reduced, which in turn leads to reduced load noise radiated by the tank walls 22.

[0049] The transformer operates at a given network frequency. Usually, the network frequency is 50 Hz or 60 Hz, which leads to structural vibrations of the at least one phase winding 12 at twice the network frequency, i.e., at 100 Hz or 120 Hz, respectively. The screen 30 may be configured to be free from structural resonances at twice the network frequency. In some embodiments, the screen 30 is configured to be free from structural resonances in a range of up to six times the network frequency. Thereby, the screen 30 will not be significantly excited by vibrations transferred from the at least one phase winding 12, through the incompressible medium, to the screen 30.

[0050] Optionally, as shown in FIG. 6, the inner surface of the screen 30 may comprise a volumetrically compressible lining 34. Bulk modulus of the lining should be significantly less than the bulk modulus of the surrounding incompressible medium. As an example, the bulk modulus of an electrically insulating transformer oil is approximately 1.7 GPa. In this example, the bulk modulus of the lining may be less than 1.7 GPa, e.g., 0.1 - 0.2 GPa, or even less.

[0051] As an alternative, instead of being rigid, the screen 30 may comprise a granular material, such as a heavy lump mass without stiffness but with significant intrinsic damping. The screen may be configured as a plurality of pockets 38, as shown in FIG. 7, which pockets 38 comprise the granular material, such as sand. The exemplary embodiment of FIG. 7 only shows a section of the screen 30. As in the other embodiments, the screen 30 is intended to circumscribe the transformer 10. The granular material should be heavy in relation to the incompressible medium. As an example, where an electrically insulating transformer oil has a density of approximately 870 kg/m.sup.3, the granular material may have a density higher than 870 kg/m.sup.3, and may be at least 1600 kg/m.sup.3.

[0052] Such a screen 30, comprising the granular material, may be arranged on the walls 22 of the transformer tank. Accordingly, the screen 30, comprising the granular material, may be arranged on the inside of the walls 22 of the transformer tank. As such, pockets 38 comprising the granular material may be attached to the walls 22 by conventional fixing means, and may be completely covering the walls 22.

[0053] The screen 30 may, in addition to being distanced from the at least one phase winding 12 of the transformer 10, also be arranged distanced from the walls 22 of the transformer tank 20. Any of the rigid screen, the compound screen or the granular screen described above may be arranged in the transformer tank 20 distanced from both the at least one phase winding 12 of the transformer 10 and from the tank walls 22. The screen 30 comprising the granular material may be arranged distanced from the tank walls 22 using a support structure (not shown) for suspending the pockets 38, containing the granular material, in the incompressible medium.

[0054] The transformer 10 may have a first extension along a first axis z parallel with the coil axis c, a second extension along a second axis x and a third extension along a third axis y. The first, second and third axes are perpendicular to each other. The transformer 10 has lateral sides parallel with the coil axis c.

[0055] The screen 30 may have at least one lateral part 32 aligned in the lateral sides of the transformer 10. The at least one lateral part 32 of the screen 30 circumscribes the transformer 10. The at least one lateral part may have a height h along the first axis z. The height h of the at least one lateral part 32 may be equal to a height H of the at least one phase winding 12. In case of multiple lateral parts 32, the sum of the individual heights h may be equal to, or less, than the height H of the at least one phase winding 12. For the purpose of cooling of the at least one phase winding 12, the sum of the heights h of the individual lateral parts may be less than the height H of the at least one phase winding 12.

[0056] The transformer 10 may have a first end along the first axis z and an opposite second end along the first axis z. The transformer tank 20 further has a first wall 22 extending transversely to the first axis z and an opposite second wall 22 extending transversely to the first axis z.

[0057] As stated in the Summary of the present disclosure, the transformer 10 is defined to have a height equal to a height H of the at least one phase winding 12, which height of the phase winding 12 also includes thicknesses of pressplates 14, 14 arranged at the ends of the phase windings 12. Thus, the first end of the transformer 10 is herein defined as comprising at least one first pressplate 14 of the at least one phase winding 12 and the second end of the transformer 10 is defined as comprising at least one second pressplate 14 of the at least one phase winding 12.

[0058] As shown in FIG. 2, the at least one lateral part 32 of the screen 30 may comprise two lateral parts 32. One lateral part 32 is arranged at the first end of the transformer 10 and one lateral part 32 is arranged at the second end of the transformer. Such a configuration may be preferable because it is envisaged that acoustic pressure in the incompressible medium is higher at the ends of the at least one phase winding 12, i.e., in the vicinity of the first pressplate 14 and the second pressplate 14. Therefore, arranging the lateral parts 32 around the first and second ends of the transformer 10 may be an efficient manner of blocking inertia-forces of the incompressible medium while leaving a major part of the at least one phase winding 12 without a screen in order to improve cooling efficiency of the incompressible medium around the at least one phase winding 12.

[0059] FIG. 3 and FIG. 4 show another configuration, where the screen 30 has a close-fitting contour in relation to the at least one phase winding 12. In the depicted example, the screen 30 comprises two lateral parts 32, each comprising three connected tubular parts 32a, 32b, 32c conforming to cylindrical shapes of three phase windings 12. In this manner, the screen 30 is equidistantly, but closely spaced from the at least one phase winding 12 around the circumference of the coil turns, resulting in efficient blocking of inertia-forces of the incompressible medium.

[0060] FIG. 5 shows a further configuration of the screen 30, where the screen 30 has at least one first part 32 and at least one second part 32, each extending transversely to the first axis z and wherein the at least one first part 32 is arranged between the first end of the transformer 10 and the first wall 22 of the transformer tank 20 and the at least one second part 32 is arranged between the second end of the transformer 10 and the second wall 22 of the transformer tank 20. Thereby, the screen 30 is configured to cover a larger portion of the transmission path of inertia-forces arising from vibration of the ends of the at least one phase winding 12. If the at least one lateral part 32 and the first part 32 and the second part 32 are applied in combination, the first part 32 and the second part 32 may be mechanically connected, such as welded to lateral parts 32.

[0061] The rigid screen, the screen comprising the volumetrically compressible lining 34 and the screen comprising the granular material may all be configured according to the embodiments shown in FIGS. 1-5. However, only the screen comprising the granular material may advantageously be arranged directly on the transformer tank walls 22.

[0062] FIG. 8 shows simulated results of how acoustic power of a transformer tank varies with frequency. Curve B shows a transformer arrangement 100 according to the present disclosure, having a screen 30 comprising a volumetrically compressible lining 34. Curve A shows a transformer arrangement without a screen, i.e., a conventional transformer arrangement. It can be seen that the screen 30 contributes significantly to load noise reduction.