Compensation structure for reducing circulating current in window of transformer and transformer comprising compensation structure

Abstract

A compensation structure for reducing circulating current in a window of a transformer and a transformer comprising the compensation structure. The compensation structure for reducing circulating current in a window of a transformer, the transformer comprising a winding (20), a metal frame (10) and a lead (50) located on one side of the frame and spaced apart from the frame, the frame (10) comprising a border and a core (14) located inside a window enclosed by the border, the winding (20) being arranged around the core (14), wherein the compensation structure comprises at least one compensator (30; 30') arranged on the border of the frame (10), the at least one compensator (30; 30') being made of silicon steel sheet of magnetic material, and the at least one compensator separates at least a part of the border of the frame from a part (50) of the lead. The compensation structure separates the iron structure between the high voltage side and the low voltage side, increases the impedance between the window circuit of the frame and the current circuit of the external lead, thereby significantly reducing the induced current within the frame and avoiding harmful effects.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of transformers, and more particularly, to a compensation structure for reducing circulating current in a transformer window and a transformer comprising the compensation structure. BACKGROUND

[0002] In some transformers, the axial component of the winding current and its lead current can be equivalent to a current circuit parallel to the core window. The magnetic field of the current circuit will induce circulating current on the metal structural elements of the core window. On the one hand, the circulating current causes additional losses on the metal structural elements; on the other hand, the circulating current will generate hot spots on the connecting parts of the metal structural elements, thereby causing gas generation problems and quality problems.

[0003] So far, the common solutions for solving these problems include:

[0004] 1. A copper compensation ring is provided on the surface of the metal frame, and by using the high conductivity and reliable connection of copper, the copper compensation ring becomes the main path of the induced circulating current and has a shielding effect on other metal parts; however, this copper compensation ring solution results in large losses on the copper ring and requires occupying part of the space of the core, with high total cost.

[0005] 2. A bypass cable or short-circuit copper bar is added in the window structure of the frame, and this structure is used to realize some connection points to be short-circuited, at which faults are prone to occur; however, this solution cannot be applied to all circulating current nodes, and therefore cannot guarantee 100% problem solving.

[0006] 3. The metal structural elements are designed to have a full insulation structure; however, the full insulation structure solution is only applicable to the case where there is a low induced voltage in the window, otherwise the circulating current can flow into the core and other risks can be generated.

[0007] 4. The large current lead winding (such as voltage regulation and low voltage) is designed to be an even number of layers to avoid the occurrence of equivalent current circuits; however, in some cases, this solution needs to greatly increase the material cost of the solution in order to meet the parameters required by the customer.

[0008] 5. A special lead design is adopted to mutually compensate the magnetic leakage effect through the leads of different core windings; however, this solution requires a corresponding special design of the structure such as the oil tank shield. SUMMARY

[0009] To solve the above problems, an object of the present application is to provide a compensation structure for reducing circulating current in a window of a transformer, and a transformer including the compensation structure, to separate an iron structure between a high voltage side and a low voltage side, increase impedance between a window circuit of a frame and a current circuit of an external lead, thereby greatly reducing induced current within the frame and avoiding harmful effects.

[0010] According to an aspect of the present application, there is provided a compensation structure for reducing circulating current in a window of a transformer, the transformer including a winding, a metal frame, and a lead located on one side of the frame and spaced apart from the frame, the frame including boundaries and an iron core located inside a window surrounded by the boundaries, and the winding being disposed to surround the iron core, and in particular, the compensation structure includes at least one compensator disposed on the boundaries of the frame, the at least one compensator being made of a silicon steel sheet of a magnetic material, and the at least one compensator separates at least a portion of the boundaries of the frame from a portion of the lead.

[0011] In this way, the at least one compensator made of a silicon steel sheet of a magnetic material can separate an iron structure between a high voltage side and a low voltage side, thereby increasing impedance between a window circuit of a frame and a current circuit of an external lead.

[0012] In an exemplary embodiment, the boundaries of the frame include two lateral boundaries and two longitudinal boundaries, and the at least one compensator includes: two lateral compensators at either of the two lateral boundaries; and / or two longitudinal compensators at either of the two longitudinal boundaries.

[0013] In this way, the two lateral compensators and / or the two longitudinal compensators can separate an iron structure between a high voltage side and a low voltage side at appropriate positions of the transformer, which further effectively increases impedance between a window circuit of a frame and a current circuit of an external lead.

[0014] In an exemplary embodiment, the two lateral compensators are symmetrically disposed with respect to a longitudinal center axis of the frame, and / or the two longitudinal compensators are symmetrically disposed with respect to a lateral center axis of the frame.

[0015] In this way, the two lateral compensators and / or the two longitudinal compensators are symmetrically disposed, which can effectively reduce circulating current of the entire window (including the iron core of the frame and the boundary iron elements of the frame), and can prevent the circulating current from being diverted.

[0016] In an exemplary embodiment, the at least one compensator includes two longitudinal compensators, wherein the two longitudinal boundaries are two side branches respectively disposed at either side of the iron core, and the two longitudinal compensators are respectively disposed around the corresponding side branch along at least one length of the corresponding side branch.

[0017] In this way, there is a large installation space on both side branches, facilitating installation of the longitudinal compensator, and the impedance between the window circuit of the frame and the current circuit of the external lead can be effectively increased.

[0018] In an exemplary embodiment, one or more of the at least one compensator each has a ring structure extending around the boundary of the frame.

[0019] In this way, the compensator of the ring structure not only separates the longitudinal boundary from the lead, but also separates the longitudinal boundary from the core in the middle, thereby significantly reducing the circulating current of the entire window (including the core of the frame and the boundary iron element of the frame) and preventing the circulating current from being diverted.

[0020] In an exemplary embodiment, one or more of the at least one compensator each includes a first half and a second half connected to each other, there is a gap between the first half and the second half, and the cross section of one or more of the at least one compensator in the direction perpendicular to the vertical axis of the boundary of the frame is circular or rectangular.

[0021] In this way, the compensator is easy to install, and the problem of large circulating current can be effectively avoided.

[0022] In an exemplary embodiment, the cross section is square.

[0023] In this way, the compensator has a proper structure, is easy to manufacture and install, and the problem of large circulating current can be effectively avoided.

[0024] In an exemplary embodiment, one or more of the at least one compensator each has a structure extending around the boundary of the frame only on a part of the circumference of the boundary.

[0025] In this way, while ensuring that the length of the compensator remains unchanged, the cost of the compensator can be reduced, and the problem of large circulating current can also be avoided.

[0026] In an exemplary embodiment, one or more of the at least one compensator each covers only one side of the boundary of the frame close to the transformer lead.

[0027] In this way, while ensuring that the length of the compensator remains unchanged, the cost of the compensator can be reduced, and the problem of large circulating current can also be avoided.

[0028] According to still another aspect of the present application, there is provided a transformer including a winding, a metal frame, and a lead located on one side of the frame and spaced apart from the frame, the frame including a boundary and a core located within a window surrounded by the boundary, the winding being arranged to surround the core; and in particular, the transformer further includes a compensating structure for reducing circulating current in the window of the transformer as described above.

[0029] The application solves the circulating current problem from a brand new angle based on magnetic field, and has the following advantages compared with the prior art:

[0030] 1. The solution of copper compensation ring in the prior art causes large loss on the copper compensation ring, needs to occupy part of the space of the core, and has high total cost; however, the application has the advantages of small size, no additional loss, low total cost, and easy installation.

[0031] 2. The solution of bypass cable or short-circuit copper bar in the prior art cannot be applied to all circulating current nodes, and thus cannot guarantee 100% problem solving; however, the application can avoid the occurrence of large circulating current problem from its physical principle.

[0032] 3. The full insulation structure solution in the prior art is only applicable to low induced voltage of the window; otherwise, circulating current may flow into the core and cause other risks; although the ring-shaped compensator solution of the application can reduce the circulating current of the entire window (including the core of the frame and the boundary iron element of the frame), and can avoid the diversion of the circulating current.

[0033] 4. In some cases, the structure of even-layer winding in the prior art needs to greatly increase the material cost of the solution in order to meet the parameters required by the customer; however, the application has almost no modification to the traditional main structure, and needs low cost.

[0034] 5. The special lead design in the prior art is only applicable to 2 / 2 core, and the oil tank shield structure needs corresponding special design; however, the application has almost no modification to the traditional main structure, and needs low cost. BRIEF DESCRIPTION OF DRAWINGS

[0035] The accompanying drawings illustrated herein are used to provide further understanding of the present application and constitute a part of the present application; the schematic embodiments and the description thereof in the present application are used to explain the present application, but not to incorrectly limit the present application. In the drawings:

[0036] Figure 1 is a schematic perspective assembly view of a transformer including a compensation structure for reducing circulating current in a window of the transformer according to a first embodiment of the present application.

[0037] Figure 2 is a schematic perspective exploded view of a transformer including a compensation structure for reducing circulating current in a window of the transformer according to a first embodiment of the present application.

[0038] Figure 3 is a schematic perspective assembly view of a transformer including a compensation structure for reducing circulating current in a window of the transformer according to a second embodiment of the present application.

[0039] Figure 4 is a schematic perspective exploded view of a transformer comprising a compensation structure for reducing circulating currents in the window of the transformer according to a second embodiment of the present application.

[0040] Figure 5 is a schematic perspective assembled view of a transformer comprising a compensation structure for reducing circulating currents in the window of the transformer according to a third embodiment of the present application.

[0041] Figure 6 is a schematic perspective exploded view of a transformer comprising a compensation structure for reducing circulating currents in the window of the transformer according to a third embodiment of the present application.

[0042] Figure 7 is a schematic view of a compensator according to a first embodiment of the present application.

[0043] Figure 8 is a schematic partial top view when the compensator according to the first embodiment of the present application is mounted on a transformer.

[0044] Figure 9 is a schematic view of a compensator according to a second embodiment of the present application.

[0045] Figure 10 is a schematic partial top view when the compensator according to the second embodiment of the present application is mounted on a transformer.

[0046] Figure 11 is a schematic view showing the basic principle of the present application.

[0047] 10: frame; 11: core circuit; 12: lead side circuit; 13: non-lead side circuit; 14: core; 15: longitudinal boundary; 16: transverse boundary; 20: winding; 30, 30': compensator; 30a: first half; 30b: second half; X: longitudinal center axis; Y: transverse center axis; 50: lead. DETAILED DESCRIPTION

[0048] Hereinafter, the technical solutions of the embodiments of the present application will be described clearly and completely in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only some but not all of the embodiments of the present application. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the application, its application, or uses. All other embodiments resulting from the embodiments of the present application obtained by those of ordinary skill in the art without creative effort fall within the scope of the present application.

[0049] For the sake of clarity, in the description of the present application Figures 1 to 6Only some components of the transformer are shown in the figures, without showing other components that are not relevant to the inventive concept of the present application, in order to avoid confusion.

[0050] Reference is made to Figure 1 , a schematic perspective assembly view of a transformer comprising a compensation structure for reducing circulating currents in the window of the transformer according to a first embodiment of the present application is shown. In Figure 1 , the transformer comprises a metal frame 10 and two windings 20, wherein the frame 10 is made of, for example, silicon steel sheets, the frame 10 comprises boundaries and two cores 14 located within the window, and each of the two windings 20 is arranged to surround either of the two cores 14. It is to be noted that although two cores 14 are shown in the embodiment, the number of cores can vary depending on the type of transformer.

[0051] In particular, the transformer further comprises a compensation structure for reducing circulating currents in the window of the transformer. The compensation structure comprises two compensators 30 arranged on the boundaries of the frame 10, wherein both of the two compensators 30 are made of silicon steel sheets of magnetic material, and the two compensators 30 separate a portion of the boundaries of the frame 10 from a portion of the lead 50.

[0052] Specifically, the four boundaries of the frame 10 are in the form of a rectangular structure, comprising two lateral boundaries 16 extending parallel to the longitudinal central axis X of the frame 10 and two longitudinal boundaries 15 extending parallel to the transverse central axis Y of the frame 10; the two longitudinal boundaries 15 are two side branches arranged on both sides of the core 14. The two compensators 30 can be referred to as longitudinal compensators, and each is arranged around the corresponding longitudinal boundary 15 along at least one length of the corresponding longitudinal boundary 15. The two compensators 30 are symmetrically arranged with respect to the transverse central axis Y of the frame 10. The two compensators 30 can be mounted to the longitudinal boundaries 15 in various ways; for example, the compensators can be connected by a strap, or can be adhered by an adhesive, or can be mounted by a clamping piece of an insulating structure, etc.

[0053] It should be noted that in the three embodiments shown in the present application, the compensators are all longitudinal compensators arranged on the longitudinal boundaries 15. However, it should be understood that all types of compensators shown in the present application can also be arranged on the lateral boundaries 16 of the frame 10, which can be referred to as lateral compensators. The lateral compensators are not shown in the drawings of the present application, but one or more lateral compensators can be applied in the transformer depending on the specific requirements.

[0054] By separating a portion of the longitudinal boundaries 15 of the frame 10 from a portion of the lead 50 through the two compensators 30, the impedance between the window circuit of the frame 10 and the current circuit of the external lead 50 is increased, thereby significantly reducing the induced current within the frame 10 and avoiding harmful effects.

[0055] Figure 11 are schematic views showing the basic principle of the present application. From Figure 11 It can be seen that an induced current will be generated between the two iron structures (e.g. the frame 10 made of silicon steel sheets and the lead 50 made of metallic material) between the high voltage side and the low voltage side, and the induced current within the frame 10 can be greatly reduced by the toroidal compensator 30 provided on the frame 10.

[0056] With reference to Figure 2 , a schematic perspective exploded view of a transformer comprising a compensating structure for reducing circulating currents in the window of the transformer according to a first embodiment of the present application is shown. The specific structure of the transformer and its two compensators 30 can be seen more clearly from the figure, wherein the transformer comprises a core circuit 11, a lead side circuit 12 and a non-lead side circuit 13. Each compensator 30 comprises a first half 30a and a second half 30b connected to each other, and the cross section of each compensator 30 in the direction of the vertical axis perpendicular to the longitudinal border 15 is rectangular. Of course, it is conceivable that each compensator 30 can have any shape suitable to surround the longitudinal border 15, e.g. circular, elliptical, square, polygonal, etc. It should be noted that there is a gap between the first half 30a and the second half 30b to prevent the induced current generated by the main magnetic flux.

[0057] Furthermore, in the first embodiment shown in Figure 1 and 2 , the first half 30a and the second half 30b each comprise three segments; however, it should be understood that the first half 30a and the second half 30b can comprise other number of segments according to specific application scenarios and design requirements, and of course can comprise only one segment.

[0058] In the first embodiment, the compensator 30 is not only able to separate a part of the longitudinal border 15 from a part of the lead 50, but also able to separate the longitudinal border 15 from the core 14, thereby significantly reducing the circulating current of the entire window (including the core of the frame and the border iron element of the frame) and being able to prevent the circulating current from being diverted.

[0059] With reference to Figure 3 and 4 , a schematic perspective assembly view and a schematic perspective exploded view of a transformer comprising a compensating structure for reducing circulating currents in the window of the transformer according to a second embodiment of the present application are shown. Figure 3 and Figure 4 The transformer shown in Figure 1 and Figure 2 is similar to that shown in Figure 3 and Figure 4Each compensator 30' in the second embodiment mainly covers one side of the longitudinal boundary 15 of the frame 10 close to the transformer lead 50. The compensator of this structure can be called a semi-annular compensator, and the other three sides of each longitudinal boundary 15 are substantially not covered by the compensator 30'.

[0060] The semi-annular compensator 30' in the second embodiment is mainly used to separate the longitudinal boundary 15 from the lead 50 so as to increase the impedance between the window circuit of the frame and the current circuit of the external lead and reduce the induced current at the lead side. Compared with the annular compensator 30 in the first embodiment, the semi-annular compensator 30' can reduce the cost while also avoiding the problem of large circulating current.

[0061] Reference is made to Figure 5 and Figure 6 , which show a schematic perspective assembly view and a schematic perspective exploded view of a transformer comprising a compensating structure for reducing circulating current in a window of the transformer according to a third embodiment of the present application. Figure 5 and Figure 6 The transformer shown in Figure 1 and Figure 2 is similar to that shown in Figure 5 and 6 , except that Figure 1 the annular compensator 30 in Figure 3 and the semi-annular compensator 30' in The combination of the annular compensator 30 and the semi-annular compensator 30' effectively avoids the problem of large circulating current.

[0062] Reference is made to Figure 7 and Figure 8 , which show a perspective view of the annular compensator 30 and a schematic partial top view when the compensator 30 is installed on the frame 10 of the transformer. Reference is made to Figure 9 and Figure 10 , which show a perspective view of the semi-annular compensator 30' and a schematic partial top view when the compensator 30' is installed on the frame 10 of the transformer.

[0063] In the first to third embodiments of the present application, the compensating structure for reducing circulating current in a window of a transformer can separate the iron structure between the high-voltage side and the low-voltage side of the transformer and increase the impedance between the window circuit of the frame and the current circuit of the external lead, thereby significantly reducing the induced current within the frame and avoiding harmful effects.

[0064] It should be noted that the terms used in the specification are merely for the purpose of describing particular embodiments and are not intended to limit the example embodiments according to the present application. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise, and it will be understood that the terms "comprise" and / or "include" specify the presence of stated features, steps, operations, devices, components and / or combinations thereof, when used in this specification.

[0065] It should be understood that the dimensions of the components shown in the drawings are not drawn according to actual proportional relationships for ease of description. Techniques, methods and devices known to those of ordinary skill in the relevant art can not be discussed in detail, but should be considered as part of the specification where appropriate. In all examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not limiting. Therefore, other examples of the example embodiments can have different values.

[0066] The above is only the preferred embodiments of the present application. It should be pointed out that those of ordinary skill in the art can make further improvements and modifications without departing from the principles of the present application, and these improvements and modifications should also belong to the protection scope of the present application.

Claims

1. A compensation structure for reducing circulating currents in a window of a transformer, the transformer comprising a winding (20), a metal frame (10) and a lead (50), the lead being located at one side of the frame (10) and spaced apart from the frame (10), the frame (10) comprising a border and a core (14), the core being located inside a window enclosed by the border, the winding (20) being arranged around the core (14), characterized in that the compensation structure comprising at least one compensator (30; 30') arranged on the border of the frame (10), wherein the at least one compensator (30; 30') is made of a silicon steel sheet of a magnetic material and separates at least a portion of the border of the frame (10) from a portion of the lead (50). the border of the frame (10) comprises two lateral borders (16) and two longitudinal borders (15) and the at least one compensator (30; 30') comprises:

2. The compensation structure for reducing circulating current in a window of a transformer of claim 1, wherein, two lateral compensators at either one of the two lateral borders (16); and / or two longitudinal compensators at either one of the two longitudinal borders (15).

3. The compensation structure for reducing circulating currents in a window of a transformer according to claim 2, characterized in that the two lateral compensators are symmetrically arranged with respect to a longitudinal center axis (X) of the frame (10), and / or the two longitudinal compensators are symmetrically arranged with respect to a lateral center axis (Y) of the frame (10). the at least one compensator (30; 30') comprises two longitudinal compensators, wherein the two longitudinal borders are two side branches each arranged at either side of the core and the two longitudinal compensators are each arranged around a respective side branch along at least one length of the respective side branch.

4. The compensation structure for reducing circulating current in a window of a transformer according to claim 3, characterized by, one or more of the at least one compensator (30; 30) each have a ring-shaped structure extending around the border of the frame.

5. The compensation structure for reducing circulating current in a window of a transformer of claim 1, wherein, the one or more compensators each comprise a first half (30a) and a second half (30b) connected to each other, wherein there is a gap between the first half and the second half and the one or more compensators have a circular or rectangular cross-section in a direction perpendicular to a vertical axis of the border of the frame (10).

6. The compensation structure for reducing circulating current in a window of a transformer of claim 5, wherein, the cross-section is square.

7. The compensation structure for reducing circulating current in a window of a transformer of claim 6, wherein, one or more of the at least one compensator (30; 30') each have a structure extending around the border of the frame (10) only over a portion of a circumference of the border.

8. The compensation structure for reducing circulating current in a window of a transformer of claim 1, wherein, the one or more compensators only cover one side of the border of the frame (10) close to the lead (50) of the transformer.

9. The compensation structure for reducing circulating current in a window of a transformer of claim 8, wherein, the transformer further comprises a compensation structure for reducing circulating currents in a window of a transformer according to any one of claims 1 to 9.

10. A transformer comprising a winding (20), a metal frame (10) and a lead (50) located at one side of the frame (10) and spaced apart from the frame (10), the frame (10) comprising a border and a core (14) located within a window enclosed by the border, the winding (20) being arranged around the core (14), characterized in that, ​

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