Cooling arrangement for cooling transformers

Abstract

This disclosure relates to a cooling arrangement (1) for cooling a transformer (10) in a transformer box (12), the cooling arrangement (1) comprising: a transformer box (12) at least partially filled with an electrically insulating fluid during use; a transformer (10) having windings (16); at least one heat exchanger (18); a fluid discharge device (20) arranged in the transformer box (12) and fluidly connected to the at least one heat exchanger (18); and a pump (22) in fluid communication with the at least one heat exchanger (18) and the fluid discharge device (20). The fluid discharge device (20) includes at least one Coanda effect fluid flow multiplier (21) configured to discharge cooled fluid along a discharge axis (c) toward one or more windings of the windings (16) of the at least one phase arm (14) of the transformer (10).

Description

Technical Field

[0001] This disclosure relates to a cooling arrangement for cooling a transformer. In particular, the invention relates to a cooling arrangement including a fluid discharge device comprising a fluid flow multiplier toward one or more windings of the transformer. Background Technology

[0002] Transformers may involve large currents, which generate heat and thus cause heat loss (as a direct consequence). Normal operation of a transformer requires the release of heat into the surrounding environment.

[0003] Transformers are housed in transformer tanks filled with an electrically insulating fluid (such as oil) into which the transformer is immersed. This insulating fluid also serves as a cooling medium. Most oil cooling is achieved through external devices such as heat exchangers, radiators, and coolers, through which the transformer oil circulates and is cooled. Due to natural convection within the transformer tank, and in the case of forced convection of the oil, a temperature profile is formed for the oil, with the temperature increasing from the bottom to the top of the transformer tank and along the transformer windings. Figure 1 As shown, oil temperature determines the boundary conditions of winding temperature. Therefore, the winding follows a similar curve from bottom to top. However, some local temperature variations also exist. The winding generates radial flux density variations, which cause radial eddy current losses, especially at the ends of the winding. Combined with the relatively hotter fluid at the top of the winding, radial eddy current losses can lead to hot spot problems, i.e., locally higher temperatures in the top portion of the winding.

[0004] Therefore, it is necessary to change the oil temperature profile to reduce winding temperature and hot spot temperature. Summary of the Invention

[0005] Therefore, the object of this disclosure is to provide improved fluid circulation in transformer tanks. Specifically, the object of this disclosure is to provide an improved cooling arrangement that utilizes the Coanda effect to circulate fluid, thereby improving fluid entrainment and induction in transformer tanks.

[0006] According to a first aspect of this disclosure, this objective is achieved at least in part by the cooling arrangement according to claim 1.

[0007] Therefore, a cooling arrangement for cooling a transformer in a transformer tank is provided. The cooling arrangement includes a transformer tank, which is at least partially filled with an electrically insulating fluid during use. The cooling arrangement further includes a transformer, which includes at least one phase arm having windings coaxially arranged on a coil axis. The transformer is enclosed in the transformer tank and is at least partially immersed in the fluid during use. The cooling arrangement includes at least one heat exchanger outside the transformer tank. The at least one heat exchanger is in fluid communication with the transformer tank and is configured to receive heated fluid from the transformer tank and supply cooled fluid to the transformer tank. A fluid discharge device is arranged in the transformer tank and fluidly connected to the at least one heat exchanger to receive cooled fluid from the at least one heat exchanger and discharge the cooled fluid into the interior of the transformer tank. A pump is in fluid communication with the at least one heat exchanger and the fluid discharge device and is configured to pump cooled fluid from the at least one heat exchanger to the fluid discharge device. The fluid discharge device includes at least one Coanda effect fluid flow multiplier configured to discharge cooled fluid along the discharge axis toward one or more windings of the at least one phase arm of the transformer.

[0008] The term "air multiplier" is used in the prior art and is therefore known to those skilled in the art. An air multiplier is typically used as a nozzle in a bladeless fan. Similarly, in this disclosure, the term "fluid flow multiplier" can refer to any type of fluid discharge device / nozzle designed to discharge fluid through an outlet typically in the form of one or more elongated slits, such that fluid around the discharge device is carried away by the fluid discharged from the outlet. Another term that can be used instead of fluid flow multiplier is Coanda effect fluid flow multiplier. The design of such fluid discharge device can vary considerably, but it is typically formed as a hollow profile similar to an extrusion, although any other suitable shape is possible. The profile typically has an elongated cross-sectional shape, and the outlet is typically configured to discharge fluid in a direction extending along a longitudinal axis along the length of the elongated cross-sectional shape. The profile may have an aerodynamic foil shape. The outlet can be located anywhere along the length of the profile's cross-sectional shape, such as at the front end of the profile (facing the incoming ambient fluid), at the rear end of the profile facing the discharge direction of the fluid flow multiplier, or somewhere between the front and rear ends of the profile. The profile can be straight, but is typically curved to form a ring surrounding the inner cross-sectional area of ​​the fluid flow multiplier.

[0009] The fluid flow multiplier may have a convex wall portion, wherein the outlet can be configured such that fluid is discharged adjacent to and along the bend, with the discharged fluid "adhering" to the bend wall portion. This results in a stronger suction effect on the ambient fluid on the opposite side of the discharged fluid flow with respect to the bend wall portion.

[0010] In this disclosure, the fluid is primarily an electrically insulating liquid medium, such as oil. Therefore, terms such as "liquid multiplier" or "oil multiplier" can be used to refer to a fluid flow multiplier or a Coanda effect fluid flow multiplier. The fluid discharge device can be immersed in the fluid within the transformer tank along with the transformer.

[0011] A pump can be fluidly connected upstream or downstream of the at least one heat exchanger. The cooling arrangement may include multiple heat exchangers and multiple pumps. The pump can supply cooled fluid to a fluid discharge device via at least one fluid conduit. The cooled fluid is then discharged along the discharge axis toward one or more windings of the at least one phase arm of the transformer. The fluid cools the transformer windings and is heated in the process. Due to natural and forced convection, the fluid rises to the top of the transformer tank and is supplied from the top to the at least one external heat exchanger. Therefore, the cooling arrangement is a closed system in which a constant volume of fluid circulates.

[0012] Each phase of a transformer has one phase arm. A phase arm may include multiple windings, such as a high-voltage winding, a low-voltage winding, and possibly one or more additional windings, such as a tertiary winding. The windings may be arranged coaxially along the coil axis. When a transformer is assembled in a transformer tank, the coil axes (or multiple coil axes in the case of a multiphase transformer) are typically vertically aligned. However, the coil axes may also be substantially horizontal, such as in the case of a traction transformer. The windings of the phase arm may be arranged along a central core post, which is inductively and mechanically connected at its ends to the core post of any other phase arm via a yoke.

[0013] Optionally, the fluid discharge device is arranged at a certain distance from the transformer. When the fluid discharge device is arranged at a certain distance from the transformer (e.g., from the transformer windings), the Coanda effect is better utilized. Thus, the fluid can be more freely entrained and / or induced by the fluid discharged from the fluid discharge device.

[0014] Optionally, each of the at least one fluid flow multiplier forms a loop around a discharge axis, and wherein the at least one loop includes a fluid outlet configured to discharge fluid along the discharge axis.

[0015] The loop extends around the discharge axis and can have different shapes, such as circular, elliptical, or polygonal. The loop can be a closed loop around the discharge axis. Alternatively, the loop can be understood as extending at least 90% around the discharge axis. The fluid outlet can be directed along the discharge axis and can extend around at least a portion of the loop, such as at least 90% of the loop.

[0016] Optionally, the fluid outlet includes at least one slit extending about the discharge axis. Thus, the slit extends about 90% of the loop. Alternatively, the fluid outlet may include multiple openings distributed along the loop about the discharge axis.

[0017] Optionally, the loop is configured to entrain fluid around the loop during fluid discharge.

[0018] The loop with the fluid outlet is configured to discharge a fluid jet along the discharge axis. The fluid moving in the jet creates a negative pressure near the jet, on the side of the jet, causing fluid around the jet to be drawn in and forced to flow along the discharge axis; this phenomenon is called "entrainment".

[0019] Similarly, the jet exiting the fluid outlet along the discharge axis of the loop creates a negative pressure in the radial interior of the loop, causing the fluid upstream of the loop to be drawn through the loop in an entrainment mechanism (also known as induction) and carried along the flow direction (i.e., along the discharge axis).

[0020] Optionally, the fluid outlet is arranged to discharge fluid along at least one curved surface of the loop to entrain fluid along the discharge axis via the Coanda effect. The curved or convex surface can be arranged on the radially inner or outer surface of the loop. As the fluid flow is discharged along the curved surface, the negative pressure on the side of the jet facing the curved surface causes the jet to "adhere" to the surface and follow its curvature. The curved surface can be configured such that the fluid flows radially away from the discharge axis. This further reduces the pressure inward along the loop path and enhances entrainment / induction.

[0021] Optionally, the at least one fluid flow multiplier is arranged coaxially with the winding, such that the discharge axis is aligned with the coil axis, and the fluid discharge device is arranged to discharge fluid along the coil axis toward the end of the winding. Therefore, fluid flow along the winding is improved.

[0022] Optionally, the adjacent coaxially arranged windings of the at least one phase arm are separated from each other by at least one gap, and wherein the loop of the at least one fluid flow multiplier is aligned with the at least one gap to inject fluid into the gap during fluid discharge.

[0023] Therefore, the gap between the windings extends coaxially with the windings along the coil axis. When at least one loop of the fluid flow multiplier is aligned with the gap between adjacent coaxial windings, fluid flow is directed into the gap. This improves fluid flow between the windings.

[0024] Optionally, the winding of the at least one phase arm includes a plurality of gaps, and wherein the fluid discharge device includes a plurality of fluid flow multipliers, each fluid flow multiplier including a loop around the discharge axis, each fluid flow multiplier being aligned with a corresponding coaxial gap to inject fluid into the gap during fluid discharge.

[0025] Therefore, when multiple coaxial windings include gaps between every two adjacent coaxial windings, the fluid discharge device may include a fluid flow multiplier / loop for each respective gap, thereby discharging fluid flow into each gap.

[0026] Optionally, the transformer box has a bottom during use, wherein the transformer is vertically arranged above the bottom of the box, and wherein the fluid discharge device is arranged to entrain fluid from the bottom of the box during fluid discharge.

[0027] In transformer tanks with conventional cooling arrangements, cold fluid may accumulate at the bottom of the tank due to its higher density compared to hotter fluids. Conventional cooling arrangements may struggle to circulate this cold fluid. However, due to fluid entrainment occurring around the fluid discharge device, including the Coanda effect fluid flow multiplier according to this disclosure, the cold fluid at the bottom of the tank can be entrained by the fluid flow multiplier located near the bottom of the tank. This improves the efficiency of the cooling arrangement because the cold fluid is utilized to a greater extent.

[0028] Optionally, the transformer includes multiple phase arms, and the cooling arrangement includes multiple fluid discharge devices, wherein the discharge axis of each fluid discharge device is aligned with the corresponding coil axis of each phase arm, such that each fluid discharge device is arranged to discharge cooled fluid toward the winding of the corresponding phase arm of the transformer.

[0029] Accordingly, each phase arm may be provided with a fluid discharge device. As described above, each fluid discharge device may include at least one Coanda effect fluid flow multiplier.

[0030] Alternatively, the fluid conduit is arranged to provide a separately predetermined fluid flow rate from the outlet of the loop of the at least one fluid flow multiplier.

[0031] Depending on the arrangement and configuration of the at least one fluid flow multiplier in the fluid discharge device, the fluid flow multiplier may be provided with a fluid conduit, which may be configured to provide a certain fluid flow rate to the fluid flow multiplier, thereby generating a predetermined fluid flow rate from the outlet of the fluid flow multiplier. In the case of multiple fluid flow multipliers, each fluid flow multiplier may have a fluid conduit, which is arranged to provide an individually predetermined fluid flow rate from the outlet of each of the respective fluid flow multipliers. Thus, fluid discharge toward the winding and / or to any gap between the windings can be configured and adapted to optimize temperature reduction along the windings and reduce hot spot temperatures.

[0032] Optionally, the size of the fluid conduit is determined to provide a predetermined fluid flow rate from the loop, and the fluid conduit is fluidly connected to the loop.

[0033] Therefore, a predetermined fluid flow rate can be set individually by the size of the fluid conduit. In the case of multiple fluid flow multipliers, the size of the fluid conduit leading to the respective fluid flow multiplier can be determined to provide a predetermined fluid flow rate from the fluid flow multiplier in question. Each fluid flow rate can be determined for the specific location and purpose of the respective fluid flow multiplier.

[0034] Optionally, the cooling arrangement further includes a control unit connected to the valve, wherein the control unit is configured to control the controllable valve to provide a predetermined fluid flow rate from the outlet of the loop of the at least one fluid flow multiplier.

[0035] The control unit and controllable valves provide the possibility of regulating the fluid flow rate from each of the at least one loop / fluid flow multiplier during transformer operation. The controllable valves can be connected to fluid conduits outside the transformer tank to avoid interfering with the electromagnetic field inside the tank during transformer operation.

[0036] Optionally, the at least one phase arm is provided with at least one temperature sensor communicatively connected to the control unit, and wherein a predetermined fluid flow rate is set based on the temperature measurement value of the at least one temperature sensor.

[0037] At least one temperature sensor, and preferably multiple temperature sensors, may be disposed on the at least one phase arm. Any temperature sensor may be arranged on the winding of the phase arm. Multiple temperature sensors may be distributed along the axial length and / or along the circumference of each winding of the phase arm. Thus, the temperature profile of each winding can be monitored, and the fluid flow rate from each fluid flow multiplier can be adjusted via a controllable valve to optimize fluid flow according to the corresponding temperature profile.

[0038] The foregoing aspects, the appended claims, and / or the examples disclosed above and below herein may be appropriately combined with each other, as will be apparent to those skilled in the art.

[0039] Additional features and advantages are disclosed in the following description, claims and drawings, and some of these features and advantages will be apparent to those skilled in the art or to those who will recognize them by practice of the disclosure herein. Attached Figure Description

[0040] Further objects, advantages, and features of this disclosure will become apparent from the following description of one or more embodiments with reference to the accompanying drawings, in which:

[0041] Figure 1 An example of temperature in a prior art transformer arrangement is shown.

[0042] Figure 2 An example of temperature in a transformer arrangement including a cooling arrangement according to the first aspect of this disclosure is shown.

[0043] Figure 3 A schematic example of a cooling arrangement configuration according to the first aspect of this disclosure is shown.

[0044] Figure 4 Another schematic example of a cooling arrangement configuration according to the first aspect of this disclosure is shown.

[0045] Figure 5 A top-down view of the fluid discharge device of the first aspect of this disclosure is shown.

[0046] Figure 6 It shows Figure 5 A cross-sectional side view of the fluid discharge device.

[0047] Figure 7 It shows Figure 5 A cross-sectional side view of the fluid discharge device.

[0048] Figure 8 An exemplary arrangement of a fluid discharge device with a transformer phase arm is shown.

[0049] Figure 9 An exemplary arrangement of a fluid discharge device including two fluid flow multipliers is shown.

[0050] Figure 10 An exemplary arrangement of multiple phase arms is shown, each phase arm being provided with a fluid discharge device.

[0051] Figure 11 An exemplary arrangement of a fluid flow multiplier connected via a fluid conduit is shown.

[0052] Figure 12 An exemplary arrangement of a fluid flow multiplier connected via a fluid conduit is shown. Detailed Implementation

[0053] This disclosure will now be expanded in more detail with reference to the accompanying drawings, which illustrate exemplary embodiments. This disclosure should not be construed as limiting oneself to the described exemplary embodiments. Throughout the specification, similar reference numerals refer to similar elements.

[0054] The terminology used herein is for the purpose of describing specific aspects of this disclosure only and is not intended to limit the invention. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains.

[0055] As discussed in the background section above, transformers can be housed in transformer cases filled with an electrically insulating fluid (such as oil) into which the transformer is immersed. The insulating fluid can also serve as a cooling medium. Most cooling is achieved through external devices such as heat exchangers, radiators, and coolers, through which the fluid circulates and is cooled. Due to natural convection within the transformer case, and under forced convection of the fluid, a temperature profile is formed for oil, with the temperature increasing from the bottom to the top of the transformer case and along the transformer windings, such as… Figure 1 The prior art example illustrates the temperatures in a prior art transformer arrangement. The figure shows how the fluid temperature O', winding temperature W', and hot spot temperature S' can vary with the vertical height H of the prior art transformer arrangement.

[0056] Figure 2 The figure illustrates a comparison between a prior art transformer arrangement and a cooling arrangement 1 according to a first aspect of this disclosure. Dashed lines indicate temperatures in the prior art transformer arrangement. The figure shows how the cooling arrangement 1 of this disclosure significantly reduces the fluid temperature O and winding temperature W, particularly in the vertically higher portions of the transformer arrangement. Hot spot temperatures S are also shown to be reduced. This figure assumes vertically aligned windings, but the cooling arrangement 1 of this disclosure is also applicable to traction transformers with substantially horizontally aligned windings.

[0057] Figure 3An example of a cooling arrangement 1 for cooling a transformer 10 within a transformer housing 12 is shown. The cooling arrangement 1 includes a transformer housing 12, which is at least partially filled with an electrically insulating fluid during use. The insulating fluid may be oil, such as mineral oil. The transformer 10 includes at least one phase arm 14 having a winding 16 arranged coaxially along a core post 15 on a coil axis a. Clearly, the transformer 10 is supported on the base plate of the transformer housing 12. However, for simplicity of the drawings, any supporting structure for the transformer 10 has been omitted. The transformer 10 is enclosed within the transformer housing 12 and at least partially immersed in the fluid. The cooling arrangement 1 further includes at least one heat exchanger 18 outside the transformer housing 12. This at least one heat exchanger 18 is in fluid communication with the transformer housing 12 and is configured to receive heated fluid from the transformer housing 12 and supply cooled fluid to the transformer housing 12. A fluid discharge device 20 is arranged in the transformer tank 12 and fluidly connected to the at least one heat exchanger 18 to receive cooled fluid from the at least one heat exchanger 18 and discharge the cooled fluid into the transformer tank 12. A pump 22 is in fluid communication with the at least one heat exchanger 18 and the fluid discharge device 20 and is configured to pump cooled fluid from the at least one heat exchanger 18 to the fluid discharge device 20. The fluid discharge device 20 includes at least one Coanda effect fluid flow multiplier 21, which is configured to discharge the cooled fluid along the discharge axis c toward one or more windings of the windings 16 of the at least one phase arm 14 of the transformer 10.

[0058] To better utilize the Coanda effect, the fluid discharge device 20 can be positioned at a distance d from the transformer 10 (e.g., from the winding 16 of the transformer 10). This allows the fluid to be more freely entrained and / or induced by the fluid discharged from the fluid discharge device. The distance d can be predetermined and can depend on transformer size, space constraints, etc.

[0059] Figure 4 The diagram shows Figure 3 An alternative advantageous configuration of the cooling arrangement 1 shown is in which the fluid flow multiplier 21 of the fluid discharge device 20 is arranged coaxially with the winding 16, such that the discharge axis c is aligned with the coil axis a, and the fluid discharge device 20 is arranged to discharge fluid along the coil axis a toward the end 28 of the winding 16. This improves the fluid flow along the winding.

[0060] Pump 22 can be fluidly connected to at least one heat exchanger 18, either upstream or downstream of the heat exchanger. Figure 3 and Figure 4In the diagram, pump 22 is shown downstream of heat exchanger 18. Cooling arrangement 1 may include multiple heat exchangers 18 and multiple pumps 22. Pump 22 may supply cooled fluid to fluid discharge device 20 via at least one fluid conduit 34. The cooled fluid is then discharged along discharge axis c toward one or more windings of the windings 16 of the at least one phase arm 14 of transformer 10. The fluid cools the transformer windings 16 and absorbs heat in the process. Due to natural and forced convection, the fluid rises to the top of transformer tank 12 and is supplied from the top to the at least one external heat exchanger 18. Cooling arrangement 1 is a closed system in which a constant volume of fluid circulates.

[0061] Each phase of transformer 10 has one phase arm 14. Phase arm 14 may include multiple windings 16, such as high-voltage windings, low-voltage windings, and possibly one or more additional windings, such as tertiary windings. The windings 16 may be arranged coaxially along coil axis a. When transformer 10 is installed in transformer tank 12, coil axis a (or multiple coil axes in the case of a multiphase transformer) is typically vertically aligned during use. However, coil axis a may also be substantially horizontal, such as in the case of a traction transformer. The windings 16 of phase arm 14 may be arranged along a central core post, which is inductively and mechanically connected at its ends to the core post of any other phase arm via a yoke (not shown).

[0062] Figures 5 to 7 The characteristics of the fluid flow multiplier 21 are illustrated. As discussed in the Summary of the Invention section, the term "air multiplier" is used in the prior art and is known to those skilled in the art. Air multipliers are typically used in nozzles in bladeless fans. Similarly, in this disclosure, the term "fluid flow multiplier" can refer to any type of fluid discharge device 20 or nozzle designed to discharge fluid through an outlet 26, typically in the form of one or more elongated slits, such that fluid around the fluid discharge device 20 is carried away by the fluid discharged from the outlet. Another term that can be used instead of fluid flow multiplier is Coanda effect fluid flow multiplier 21.

[0063] In this disclosure, the fluid is primarily an electrically insulating liquid medium, such as oil. Therefore, terms such as "liquid multiplier" or "oil multiplier" can be used to refer to the fluid flow multiplier 21 or the Coanda effect fluid flow multiplier 21. The fluid discharge device 20 can be immersed in the fluid within the transformer tank 12 along with the transformer 10.

[0064] Figure 5A fluid discharge device 20 according to the present disclosure is shown, comprising a fluid flow multiplier 21 in the form of a loop 24 about a discharge axis c, wherein at least one loop 24 includes a fluid outlet 26 configured to discharge fluid along the discharge axis c. The fluid outlet 26 may include at least one slit 26 extending about the discharge axis c. The loop 24 may have different shapes, such as circular, elliptical, or polygonal, wherein... Figure 5 A circular closed loop 24 is depicted. The fluid outlet 26 can be directed to discharge fluid along the discharge axis c and can extend around at least a portion of the loop 24, such as at least 90% of the loop. Figure 5 The slit in the example can therefore extend around at least 90% of the loop. Fluid outlet 26 can alternatively include multiple openings distributed along the loop 24 around the discharge axis c. At least one fluid conduit 34 can be arranged to fluidly connect pump 22 to fluid flow multiplier 21.

[0065] Figure 6 It shows Figure 5 A cross-sectional side view of the loop 24. The fluid discharge device 20, including the fluid flow multiplier 21 according to this disclosure, can vary significantly in design, but is typically formed as a hollow profile similar to an extrusion, an example of which is shown in... Figure 6 As shown in the details, although any other suitable shape is also possible. The profile typically has an elongated cross-sectional shape, and the outlet 26 is typically configured to discharge fluid in a direction along a longitudinal axis (e.g., discharge axis c) extending along the length L of the elongated cross-sectional shape, such as... Figure 5 As shown. The profile can have an aerodynamic foil shape. The outlet 26 can be located at any suitable location along the length L of the profile's cross-sectional shape, such as at the front end of the profile, or at the rear end of the profile facing the discharge direction of the fluid flow multiplier, or somewhere between the front and rear ends of the profile. The profile can be straight, but is typically curved to form a ring or loop 24 surrounding the inner cross-sectional region of the fluid flow multiplier 21.

[0066] Loop 24 can be configured to entrain fluid around loop 24 during fluid discharge. For this purpose, loop 24, including fluid outlet 26, can be configured to discharge a fluid jet along discharge axis c. The fluid moving in the jet creates a negative pressure or suction effect near the jet, on the sides of the jet, causing fluid around the jet to be drawn in and forced to flow along the discharge axis; this phenomenon is called "entrainment," as symbolically illustrated by arrow E. The jet is represented by multiple arrows along the radially inner circumferential wall portion of loop 24.

[0067] The jet exiting the fluid outlet around the discharge axis c of loop 24 creates a negative pressure in the radial interior of loop 24, causing the fluid upstream of the loop to be drawn through the loop and carried along the flow direction (i.e., along the discharge axis c) in an entrainment mechanism (also known as induction), as symbolically shown by arrow I.

[0068] The fluid flow multiplier 21 may have a convex or curved wall portion 27, wherein the outlet 26 may be configured such that fluid is discharged adjacent to and along the curved wall portion 27, wherein the discharged fluid "adheres" to the curved wall portion 27. This results in a stronger suction effect on the ambient fluid on the opposite side of the discharged fluid flow with respect to the curved wall portion, thereby enhancing the induction I. Figure 6 In the middle, the curved wall portion 27 forms part of the inner circumferential wall portion of the loop 24.

[0069] Figure 7 This is a cross-sectional side view of the fluid flow multiplier 21. The arrows illustrate the fluid flow through loop 24 generated by the fluid jet exiting fluid outlet 26. The density or length of the arrows is not drawn to scale and does not represent the magnitude of the flow rate. However, due to the entrainment E and induction I of the jet, the fluid flow is maximized at the downstream end of the fluid flow multiplier 21. In the example of loop 24, the fluid flow is therefore maximized at a radial distance r from the discharge axis d, which corresponds to the radius of loop 24.

[0070] In transformer tanks with conventional cooling arrangements, cold fluid may accumulate at the bottom of the tank due to its relatively higher density compared to hotter fluid. Conventional cooling arrangements may struggle to circulate this cold fluid. However, due to fluid entrainment around the fluid discharge device 20, including the Coanda effect flow multiplier 21 according to this disclosure, the cold fluid located at the bottom 32 of the tank 12 can be entrained by the flow multiplier 21 positioned near the bottom 32 of the tank 12. This improves the efficiency of the cooling arrangement 1 because the cold fluid is utilized to a greater extent. Figure 4 This arrangement is illustrated in the image.

[0071] A cross-sectional view of phase arm 14 of transformer 10 is shown. Figure 8The illustration shows how adjacent coaxially arranged windings 16a, 16b of at least one phase arm 14 can be separated from each other by at least one gap 30, wherein the loop 24 of the at least one fluid flow multiplier 21 is aligned with the at least one gap 30 to inject fluid into the gap 30 during fluid discharge. Thus, the gap 30 between windings 16a, 16b extends coaxially with windings 16a, 16b along the coil axis a. When the at least one loop 24 of the fluid flow multiplier 21 is aligned with the gap 30 between adjacent coaxial windings 16a, 16b, fluid flow is directed into the gap 30. This improves fluid flow between windings 16a, 16b, thereby reducing the temperature of windings 16a, 16b and mitigating hot spots.

[0072] Figure 9 A plurality of windings 16a, 16b, 16c of phase arm 14 are shown, wherein the windings 16a, 16b, 16c include a plurality of gaps 30a, 30b, and wherein the fluid discharge device 20 includes a plurality of fluid flow multipliers 21a, 21b, each fluid flow multiplier including a loop 24 around the discharge axis c. Each fluid flow multiplier 21a, 21b may be arranged and aligned with a corresponding coaxial gap 30a, 30b to inject fluid into the gap 30a, 30b during fluid discharge. Thus, when the plurality of coaxial windings include gaps between every two coaxially adjacent windings 16a, 16b, 16c, the fluid discharge device 20 may include a fluid flow multiplier 21 for each corresponding gap 30a, 30b, thereby discharging fluid flow into each gap 30a, 30b.

[0073] In some examples, such as Figure 10 As illustrated, transformer 10 may include multiple phase arms 14a, 14b, 14c. Therefore, cooling arrangement 1 may include multiple fluid discharge devices 20a, 20b, 20c. The discharge axis c of each fluid discharge device 20a, 20b, 20c may be aligned with the corresponding coil axis a of each phase arm 14a, 14b, 14c (e.g., ...). Figure 4 As shown, each fluid discharge device 20a, 20b, 20c is arranged to discharge cooled fluid toward the winding 16 of the corresponding phase arm 14a, 14b, 14c of the transformer 10. Therefore, each phase arm 14a, 14b, 14c may be provided with a fluid discharge device 20a, 20b, 20c. As described above, each fluid discharge device 20a, 20b, 20c may include at least one Coanda effect fluid flow multiplier 21.

[0074] In cooling arrangement 1, fluid conduits 34 can be arranged to provide a individually predetermined fluid flow rate from the outlet 26 of the fluid flow multiplier 21 of the at least one fluid discharge device 20. At least one fluid conduit 34 can fluidly connect each fluid discharge device 20 to the pump 22. Depending on the arrangement and configuration of the at least one fluid flow multiplier 21 of the fluid discharge device 20, the fluid flow multiplier 21 can be provided with fluid conduits 34, which can be configured to provide a certain fluid flow rate to the fluid flow multiplier 21, thereby generating a predetermined fluid flow rate from the outlet of the fluid flow multiplier 21. In the case of multiple fluid flow multipliers 21, each fluid flow multiplier 21 can have a fluid conduit 34, which is arranged to provide a individually predetermined fluid flow rate from the outlet 26 of each of the respective fluid flow multipliers 21. Thus, fluid discharge toward the winding 16 and / or into any gap between the winding 16 can be configured and adapted to optimize temperature reduction along the winding 16 and reduce hot spot temperatures.

[0075] Figure 11 The diagram illustrates that the dimensions of fluid conduits 34a and 34b can be determined to provide a predetermined fluid flow rate from fluid flow multipliers 21a and 21b, which are fluidly connected to the fluid flow multipliers. As shown, the fluid flow rate provided by the first fluid conduit 34a to the first fluid flow multiplier 21a is more limited compared to the second fluid conduit 34b, which is fluidly connected to the second fluid flow multiplier 21b. Therefore, the individual predetermined fluid flow rate of the fluid flow multipliers 21a and 21b can be set by the dimensions of the fluid conduits 34a and 34b. In the case of multiple fluid flow multipliers 21a and 21b, the dimensions of the fluid conduits 34a and 34b leading to the respective fluid flow multipliers 21a and 21b can be determined to provide a predetermined fluid flow rate from the fluid flow multipliers 21a and 21b in question. The dimensions of each fluid conduit 34a and 34b are determined to accommodate the fluid flow rate in order to optimize the cooling of the winding 16.

[0076] like Figure 12 As shown, the cooling arrangement 1 may further include a control unit 36 ​​connected to at least one controllable valve 38a, 38b. The control unit 36 ​​may be configured to control the at least one controllable valve 38a, 38b to provide a predetermined fluid flow rate from the outlet 26 of the fluid flow multipliers 21a, 21b of the at least one fluid discharge device 20. The control unit 36 ​​may include a user interface to enable an operator to adjust the at least one controllable valve 38a, 38b.

[0077] The control unit 36 ​​and controllable valve 38 provide the possibility of regulating the fluid flow rate from each of the at least one fluid flow multiplier 21a, 21b during operation of the transformer 10. The at least one controllable valve 38a, 38b can be connected to fluid conduits 34a, 34b outside the transformer tank 12 to avoid interfering with the electromagnetic field inside the transformer tank 12 during operation of the transformer 10. (Dashed lines illustrate...) Figure 12 The wall of transformer box 12 in the middle.

[0078] Furthermore, such as Figure 3 and Figure 4 As shown, the at least one phase arm 14 may be provided with at least one temperature sensor 40 communicatively connected to the control unit 36, and wherein a predetermined fluid flow rate is set based on the temperature measurement value of the at least one temperature sensor 40.

[0079] At least one temperature sensor, and preferably multiple temperature sensors, may be disposed on the at least one phase arm 14. Any temperature sensor may be arranged on the winding 16 of the phase arm 14. Multiple temperature sensors 40 may be distributed along the axial length and / or circumferentially along each winding 16 of the phase arm 14. Thus, the temperature profile of each winding 16 can be monitored, and the fluid flow rate from each fluid flow multiplier 21 can be adjusted via a controllable valve 38 to optimize fluid flow according to the corresponding temperature profile. In some examples, the control unit 36 ​​may communicate wirelessly with the sensors 40.

Claims

1. A cooling arrangement (1) for cooling a transformer (10) in a transformer box (12), the cooling arrangement (1) comprising: - Transformer box (12), which is at least partially filled with an electrically insulating fluid during use; - Transformer (10), the transformer including at least one phase arm (14) having a winding (16) coaxially arranged on a coil axis (a), the transformer (10) being enclosed in the transformer box (12) and at least partially immersed in the fluid; - At least one heat exchanger (18) outside the transformer box (12), the at least one heat exchanger (18) being in fluid communication with the transformer box (12) and configured to receive heated fluid from the transformer box (12) and supply cooled fluid to the transformer box (12); - A fluid discharge device (20), which is arranged in the transformer tank (12) and fluidly connected to the at least one heat exchanger (18) to receive cooled fluid from the at least one heat exchanger (18) and discharge the cooled fluid into the interior of the transformer tank (12); and - Pump (22), which is in fluid communication with the at least one heat exchanger (18) and the fluid discharge device (20) and is configured to pump cooled fluid from the at least one heat exchanger (18) to the fluid discharge device (20). The fluid discharge device (20) is characterized in that it includes at least one Coanda effect fluid flow multiplier (21) configured to discharge the cooled fluid along the discharge axis (c) toward one or more windings of the windings (16) of at least one phase arm (14) of the transformer (10).

2. The cooling arrangement (1) as described in claim 1, wherein, The fluid discharge device (20) is located at a certain distance from the transformer (10).

3. The cooling arrangement (1) as described in claim 1 or 2, wherein, Each of the at least one fluid flow multiplier (21) forms a loop (24) around the discharge axis (c), and wherein the at least one loop (24) includes a fluid outlet (26) configured to discharge fluid along the discharge axis (c).

4. The cooling arrangement (1) as described in claim 3, wherein, The fluid outlet (26) includes at least one slit (28) extending about the discharge axis (c).

5. The cooling arrangement (1) as described in claim 3, wherein, The loop (24) is configured to entrain fluid around the loop (24) during fluid discharge.

6. The cooling arrangement (1) as described in claim 3, wherein, The fluid outlet (26) is arranged to discharge fluid along at least one curved wall portion (27) of the loop (24) to entrain fluid along the discharge axis (c) via the Coanda effect.

7. The cooling arrangement (1) as described in claim 3, wherein, The at least one fluid flow multiplier is arranged coaxially with the winding (16) such that the discharge axis (c) is aligned with the coil axis (a) and the fluid discharge device (20) is arranged to discharge fluid along the coil axis (a) toward the end (28) of the winding (16).

8. The cooling arrangement (1) as described in claim 7, wherein, The adjacent coaxially arranged windings (16a, 16b) of the at least one phase arm (14) are separated from each other by at least one gap (30), and wherein the loop (24) of the at least one fluid flow multiplier (21) is aligned with the at least one gap (30) to inject fluid into the gap (30) during fluid discharge.

9. The cooling arrangement (1) as described in claim 8, wherein, The windings (16a, 16b, 16c) of the at least one phase arm (14) include a plurality of gaps (30a, 30b), and wherein the fluid discharge device (20) includes a plurality of fluid flow multipliers (21a, 21b), each fluid flow multiplier including a loop (24) around the discharge axis (c), each fluid flow multiplier (21a, 21b) being aligned with a corresponding coaxial gap (30a, 30b) to inject fluid into the gap (30a, 30b) during fluid discharge.

10. The cooling arrangement (1) as described in claim 3, wherein, The transformer box (12) has a box bottom (32) during use, and wherein the transformer (10) is arranged vertically above the box bottom (32), and wherein the fluid discharge device (20) is arranged to entrain fluid from the box bottom (32) during fluid discharge.

11. The cooling arrangement (1) as described in claim 3, wherein, The transformer (10) includes a plurality of phase arms (14a, 14b, 14c), and the cooling arrangement (1) includes a plurality of fluid discharge devices (20a, 20b, 20c), wherein the discharge axis (c) of each fluid discharge device (20a, 20b, 20c) is aligned with the corresponding coil axis (a) of each phase arm (14a, 14b, 14c), such that each fluid discharge device (20a, 20b, 20c) is arranged to discharge cooled fluid toward the winding (16) of the corresponding phase arm (14) of the transformer (10).

12. The cooling arrangement (1) as claimed in any one of claims 7 to 9, wherein, The fluid conduit (34) is arranged to provide a single predetermined fluid flow from the outlet (26) of the fluid flow multiplier (21) of the at least one fluid flow multiplier (21).

13. The cooling arrangement (1) as described in claim 12, wherein, The fluid conduit (34) is sized to provide a predetermined fluid flow rate from the fluid flow multiplier (21), and the fluid conduit (34) is fluidly connected to the fluid flow multiplier.

14. The cooling arrangement (1) as claimed in claim 12, further comprising a control unit (36) connected to a controllable valve (38), and wherein, The control unit (36) is configured to control the controllable valve (38) to provide a predetermined fluid flow rate from the outlet (26) of the fluid flow multiplier (21) of the at least one fluid discharge device (20).

15. The cooling arrangement (1) as described in claim 14, wherein, The at least one phase arm (14) is provided with at least one temperature sensor (40) communicatively connected to the control unit (36), and wherein the predetermined fluid flow rate is set according to the temperature measurement value of the at least one temperature sensor (40).

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