Multi-winding equal-band voltage-regulating transformer and manufacturing method thereof

Abstract

This invention relates to the field of power transformer manufacturing technology, and in particular to a multi-winding transformer with adjustable voltage and its manufacturing method. In the multi-winding transformer with adjustable voltage, the common coil and series coils are spliced ​​together to form the high-voltage winding, which is self-coupled with the medium-voltage winding. The high-voltage, medium-voltage, and low-voltage windings are each equipped with an independent voltage regulating unit. The high-voltage winding uses a single-bridge bridging constant flux no-load voltage regulation, eliminating the need for an independent high-voltage regulating coil. The voltage regulating tap is directly located at the end of the series coil and is equipped with a matching no-load voltage regulating tap changer. The medium-voltage and low-voltage windings use on-load voltage regulation with forward and reverse constant flux, and are each equipped with an on-load tap changer. The end of the common coil serves as the common neutral point shared by the high-voltage and medium-voltage windings. The low-voltage winding uses a fully insulated structure. This achieves completely independent voltage regulating circuits for the three windings, ensuring no interference between them, adapting to different voltage regulating modes, and maintaining a constant core flux without deviation throughout the voltage regulation process.

Description

Technical Field

[0001] This invention relates to the field of power transformer manufacturing technology, and in particular to a multi-winding transformer with adjustable voltage and its manufacturing method. Background Technology

[0002] Multi-winding voltage regulating transformers are widely used in power grid interconnection, multi-voltage power supply and new energy grid connection scenarios. They can simultaneously adapt to the voltage regulation needs of high voltage, medium voltage and low voltage multi-circuit, and meet the voltage stabilization and voltage conversion requirements of different load sides.

[0003] Existing multi-winding voltage-regulating transformers generally employ a structure combining independent high-voltage regulating coils, conventional winding arrangements, and a single voltage regulation mode. The high-voltage winding is mostly equipped with a separate high-voltage regulating coil, and the voltage regulation circuits of the medium-voltage and low-voltage windings are electrically coupled to each other, making independent control impossible. This leads to a series of structural and functional defects: 1) The winding layout is unreasonable. The setting of independent high voltage regulating coil will inevitably increase the overall size of the transformer and the core load, raising the equipment manufacturing cost and no-load loss. At the same time, it is easy to cause an imbalance in the ampere-turn distribution between windings, directly reducing the operational stability of the equipment. 2) Poor compatibility of voltage regulation modes. High voltage no-load voltage regulation and medium and low voltage on-load voltage regulation are difficult to coordinate. During conventional structure operation, problems such as magnetic flux deviation and insufficient voltage regulation accuracy are prone to occur. In addition, the common neutral point is set in a chaotic manner. The insulation protection of the neutral point shared by the high voltage and medium voltage windings is weak, which poses potential operational hazards. 3) The voltage regulation circuit lacks independence, and the voltage regulation units of each winding interfere with each other during operation. This is compounded by problems such as unreasonable design of the low-voltage fully insulated structure and voltage regulation point, and poor adaptability of the voltage regulation switch. It is very easy to cause partial discharge and insulation breakdown faults. It is impossible to achieve the dual functions of high-voltage no-excitation constant flux voltage regulation and medium and low voltage forward and reverse constant flux on-load voltage regulation at the same time. It is difficult to meet the stringent requirements of modern power grids for multi-voltage levels, high-precision voltage stabilization, and high-reliability operation.

[0004] Therefore, it is urgent for technical personnel to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a multi-winding transformer with adjustable voltage, which aims to solve the problems of bulky and loose winding layout, electrical coupling interference between voltage regulating circuits, and difficulty in compatibility and coordination of high and low voltage regulating modes in existing designs.

[0006] This invention relates to a multi-winding transformer with adjustable voltage, comprising a three-phase five-limb core, a high-voltage winding, a medium-voltage winding, and a low-voltage winding; the low-voltage winding consists of a low-voltage coil and a low-voltage regulating coil; the high-voltage winding consists of a common coil and a series coil; the medium-voltage winding includes a medium-voltage regulating coil; the low-voltage coil, the low-voltage regulating coil, the common coil, the medium-voltage regulating coil, and the series coil are wound and arranged sequentially from the inside to the outside on the core columns of the three-phase five-limb core; The high-voltage winding and the medium-voltage winding form a self-coupling connection; The high-voltage winding, medium-voltage winding, and low-voltage winding are each equipped with an independent voltage regulating unit; The high-voltage winding adopts a single-bridge bridging constant flux no-excitation voltage regulation, and does not have an independent high voltage regulation coil. The voltage regulation tap is directly opened and led out to the off-end position of the series coil. Both the medium-voltage winding and the low-voltage winding adopt on-load voltage regulation with constant flux in both directions; the voltage regulation point of the medium-voltage winding is set between the beginning of the common coil and the end of the series coil; the end of the common coil serves as the common neutral point shared by the high-voltage winding and the medium-voltage winding. The low-voltage winding has a fully insulated structure, and its voltage adjustment point is located at the end of the low-voltage coil. The high-voltage winding is equipped with an off-load tap changer; the medium-voltage winding and the low-voltage winding are each equipped with an on-load tap changer adapted to their own number of phases.

[0007] As a further improvement to the technical solution disclosed in this invention, the low-voltage coil is continuously wound with the first end extending upwards and the last end extending downwards to achieve multi-stage tapping.

[0008] As a further improvement to the technical solution disclosed in this invention, the common coil is continuously wound with the first end protruding upwards and the last end protruding downwards; the intermediate voltage regulating coil is wound with double-layer multi-helix winding, and all protrusions are led out from the bottom to form an inverted U-shaped structure.

[0009] As a further improvement to the technical solution disclosed in this invention, the series coil is composed of an upper series coil segment and a lower series coil segment connected in parallel, and is wound continuously with an inner screen; the upper series coil segment and the lower series coil segment are structurally symmetrical and have opposite winding directions.

[0010] As a further improvement to the technical solution disclosed in this invention, the non-excitation voltage regulating tap changer has a single-bridge bridging structure, including a two-phase switch adapted to phases A and B, and a single-phase switch adapted to phase C.

[0011] As a further improvement to the technical solution disclosed in this invention, the transformer is provided with a preset connection group; the low-voltage winding is connected by phase-to-phase leads to realize the preset connection group.

[0012] In addition, the present invention also discloses a preparation method for preparing a multi-winding transformer with adjustable voltage, comprising the following steps: S1. Prepare a three-phase five-column iron core and perform insulation pretreatment on its iron core columns; according to the arrangement order from the inside to the outside, wind low-voltage coil, low-voltage coil, common coil, medium-voltage regulating coil and series coil in sequence on the iron core columns, and perform interlayer insulation treatment on low-voltage coil, low-voltage coil, common coil, medium-voltage regulating coil and series coil respectively, and simultaneously reserve the corresponding output of low-voltage coil, low-voltage coil, common coil, medium-voltage regulating coil and series coil; S2. Connect the common coil and the series coil to form a high-voltage winding, and make the high-voltage winding and the medium-voltage winding form an autotransformer connection; at the preset voltage adjustment points at the end of the series coil, the beginning of the common coil, the end of the common coil, and the end of the low-voltage coil, respectively, lead out voltage adjustment taps and conventional terminals, and provide insulation protection for the voltage adjustment taps. S3. Connect the voltage regulating tap of the high voltage winding to the corresponding off-load voltage regulating tap changer, and connect the voltage regulating taps of the medium voltage winding and low voltage winding to the corresponding on-load tap changers of the corresponding phase number. S4. Complete the lead wire connection between the low voltage coil, low voltage coil, common coil, medium voltage regulating coil, series coil, voltage regulating switch and external bushing, reserve electrical insulation distance according to insulation level requirements, and insulate all exposed connection points and leads. S5. Assemble the transformer body after wiring is completed, and then conduct overall voltage regulation and insulation performance tests to verify the independent working reliability of the high voltage regulating unit, medium voltage regulating unit, and low voltage regulating unit.

[0013] As a further improvement to the technical solution disclosed in this invention, in step S1, the winding of the series coil adopts a segmented synchronous winding process, and the upper series coil segment and the lower series coil segment are wound separately; after the winding is completed, the upper series coil segment and the lower series coil segment are pre-connected in parallel, and then the interlayer insulation treatment is uniformly implemented so that the upper series coil segment and the lower series coil segment are impedance matched and the winding direction is opposite.

[0014] As a further improvement to the technical solution disclosed in this invention, in step S2, when the high-voltage winding and the medium-voltage winding are self-coupled, the common coil end is used as the common neutral point for positioning wiring, and after the wiring is completed, the neutral point is subjected to double-layer insulation sealing treatment; in step S3, the high-voltage regulating tap and the non-excitation regulating tap changer adopt a cross-connection wiring.

[0015] Regarding the topic of multi-winding transformers with adjustable voltage, its practical applications can achieve at least the following beneficial technical effects, specifically: 1) Relying on the separate design of three independent voltage regulating units—high-voltage, medium-voltage, and low-voltage windings—the three voltage regulating circuits operate independently and without interference, enabling targeted adaptation to differentiated voltage regulation conditions at different voltage levels and achieving synchronous independent voltage regulation at multiple voltage levels. Among them, the high-voltage winding adopts a single-bridge bridging constant flux no-excitation voltage regulation mode, which can stably maintain constant core flux throughout the entire operation, fundamentally avoiding the problem of flux deviation. The medium-voltage and low-voltage windings adopt a forward and reverse constant flux on-load voltage regulation mode, coupled with voltage regulating switches adapted to the number of phases of each winding, which can achieve smooth switching and precise control of voltage regulation levels, rapid voltage regulation response, and compliant regulation accuracy, thus fully adapting to the normalized and multi-scenario voltage regulation operation requirements of the power grid. 2) Abandoning the traditional independent high-voltage regulating coil structure, the high-voltage winding is integrated into a common coil and series coil splicing design, effectively compressing the axial and radial space occupied by the transformer winding, reducing the core operating load, and simultaneously optimizing the ampere-turn distribution ratio between windings. This reduces the no-load loss of the equipment from the source, while also reducing the input of raw materials and controlling the overall manufacturing cost. The high-voltage winding and the medium-voltage winding share the end of the common coil as a common neutral point. The point is set in a regular and fixed manner, which facilitates centralized insulation protection. Combined with the fully insulated low-voltage winding, the overall insulation strength of the transformer is comprehensively improved, eliminating the hidden danger of local insulation weakness. Moreover, the winding leads and voltage regulating taps are arranged in an orderly and standardized manner, greatly simplifying the winding, lead connection and overall assembly process, which helps to improve production and assembly efficiency.

[0016] Regarding the manufacturing method, the initial stage involves simultaneous completion of core insulation pretreatment, layered winding of each winding, and interlayer insulation treatment. This includes reserving voltage regulating leads and corresponding voltage regulating points for each of the high, medium, and low voltage windings, and standardizing the basic structure for voltage regulation of each winding, thus preparing for independent voltage regulation of the three windings. In the intermediate stage, the winding connection, voltage regulating tap lead-out, and tap changer wiring are completed according to the established voltage regulation design. Strict matching of the differentiated voltage regulation wiring specifications for high-voltage no-excitation and medium- and low-voltage forward and reverse regulation is ensured. Simultaneously, insulation protection of the voltage regulating points is implemented to ensure that the three voltage regulation circuits are independent and do not interfere with each other, realizing the functional zoning of voltage regulation for each winding. Ultimately, this ensures that the finished product stably achieves the core functions of independent voltage regulation of the high, medium, and low voltage windings and constant flux voltage regulation throughout the entire process. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1This is a schematic diagram of the structure of the multi-winding voltage-regulating transformer of the present invention (three-phase five-limb iron core not shown). Figure 2 This is a schematic diagram of the high-voltage and medium-voltage windings of the multi-winding transformer with voltage regulation and its voltage regulation wiring in this invention. Figure 3 This is a schematic diagram of the low-voltage winding of the multi-winding transformer with voltage regulation and its voltage regulation wiring principle of the present invention; Figure 4 This is a schematic diagram showing the connection between the low-voltage coil of the multi-winding transformer with voltage regulating function and the corresponding switch in this invention. Figure 5 This is a schematic diagram showing the connection between the series coils of the multi-winding voltage regulating transformer, the common coil lead, and the corresponding switch of the present invention (taking phase A as an example). Figure 6 This is a schematic diagram of the overall switch layout of the present invention, showing that all windings of the device have voltage regulating transformers. Figure 7 This is a schematic diagram of the operating principle of the high-voltage tap changer with multiple windings equipped with voltage regulating transformers according to the present invention.

[0019] 1-High voltage winding; 11-Common coil; 12-Series coil; 121-Upper series coil section; 122-Lower series coil section; 2-Medium voltage winding; 21-Medium voltage regulating coil; 211-Inner layer medium voltage regulating coil section; 212-Outer layer medium voltage regulating coil section; 3-Low voltage winding; 31-Low voltage coil; 32-Low voltage regulating coil; 4-Low voltage on-load tap changer; 5-Medium voltage on-load tap changer; 6-High voltage two-phase off-excitation tap changer; 7-High voltage one-phase off-excitation tap changer. Detailed Implementation

[0020] As the core equipment for achieving synchronous regulation of multiple voltage levels in a power system, the transformer's winding arrangement structure, voltage regulation mode design, and coil winding process directly determine the overall voltage regulation accuracy, long-term operational stability, and insulation safety level of the equipment, which in turn affects the overall power supply quality and reliability of the power grid.

[0021] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. Figure 1 A schematic diagram of the multi-winding voltage-regulating transformer of the present invention is shown. It can be seen that it mainly consists of a three-phase five-limb iron core (not shown in the figure), a high-voltage winding 1, a medium-voltage winding 2, and a low-voltage winding 3. The low-voltage winding 3 includes a low-voltage coil 31 and a low-voltage coil 32; the high-voltage winding 1 includes a common coil 11 and a series coil 12; and the medium-voltage winding 2 includes a medium-voltage regulating coil 21. The three-phase five-limb iron core provides mounting support and a closed magnetic circuit for all coils. The low-voltage coil 31, low-voltage coil 32, common coil 11, medium-voltage regulating coil 21, and series coil 12 are wound sequentially layer by layer on the iron core columns of the three-phase five-limb iron core from the inside out.

[0022] Depend on Figure 1 As shown, the multi-winding transformer with independent voltage regulation adopts a multi-winding independent voltage regulation structure design. The common coil 11 and the series coil 12 are fixedly connected to form a complete high-voltage winding 1. The high-voltage winding 1 and the medium-voltage winding 2 form a self-coupling connection. The high-voltage winding 1, the medium-voltage winding 2, and the low-voltage winding 3 are each equipped with an independent voltage regulation unit. The three voltage regulation units are physically separated and electrically completely independent. They do not interfere with each other or couple with each other during operation, so as to synchronously meet the differentiated voltage regulation requirements of different voltage levels, realize multi-circuit independent voltage regulation, and adapt to the multi-voltage level power supply regulation requirements under complex power grid conditions.

[0023] The aforementioned multi-winding transformers with voltage regulation are specifically designed for multi-voltage levels and multi-circuit independent voltage regulation conditions. Through the orderly arrangement of multi-layer windings and the coordinated layout of multiple voltage regulation units, they overcome the technical limitations of the mutual coupling of traditional transformer voltage regulation circuits. This enables the high-voltage, medium-voltage, and low-voltage windings to have independent voltage regulation capabilities, and each voltage regulation circuit is completely electrically isolated, which can stably meet the differentiated voltage regulation needs of different load sides.

[0024] In the design of the core voltage regulation scheme, such as Figure 2 As shown, the high-voltage winding 1 adopts a single-bridge bridging constant flux no-excitation voltage regulation method, eliminating the redundant structure of the traditional transformer with a separate high-voltage regulating coil, simplifying the overall winding layout, and effectively reducing the equipment size and core operating load. The high-voltage winding 1 does not have a separate high-voltage regulating coil; the voltage regulating tap is directly opened and led out to the end of the series coil 12. High-voltage regulation can be achieved using the structure of the series coil 12 itself, eliminating the need for an additional voltage regulating winding, thus reducing manufacturing costs and no-load losses. Both the medium-voltage winding 2 and the low-voltage winding 3 adopt a forward and reverse constant flux on-load voltage regulation method, enabling precise and smooth switching of voltage levels without power interruption, ensuring continuous power supply. The voltage regulating point of the medium-voltage winding 2 is located between the beginning of the common coil 11 and the end of the series coil 12, with a clear voltage regulation path and neat wiring points. The end of the common coil 11 serves as a common neutral point shared by the high-voltage winding 1 and the medium-voltage winding 2, with a fixed and standardized location, facilitating centralized insulation protection.

[0025] like Figure 3 As shown, the low-voltage winding 3 adopts a fully insulated structure, and the voltage adjustment points are uniformly set at the end of the low-voltage coil 31, ensuring the insulation safety of the low-voltage adjustment circuit throughout and avoiding operational hazards such as local insulation weakness and partial discharge. Figure 3 The circuit configuration and point layout of the low-voltage winding and its voltage regulating wiring are fully demonstrated.

[0026] To further optimize the winding structure performance and improve the overall voltage regulation adaptability and operational stability of the transformer, this invention employs differentiated winding processes for each coil. The low-voltage coil 31 uses a continuous winding process, with an upper exit point at the beginning and a lower exit point at the end after winding, resulting in a neat exit point layout that facilitates standardized subsequent lead connection. The low-voltage coil 32 uses a ten-helix winding process, with exit points at both the upper and lower ends after winding. The combination of these upper and lower exit points enables multi-stage voltage regulation tapping, meeting the requirements for fine multi-stage voltage regulation on the low-voltage side. The common coil 11 also uses a continuous winding process, with an upper exit point at the beginning and a lower exit point at the end after winding, adapting to the self-coupling connection structure of the high-voltage winding 1 and the medium-voltage winding 2. The medium voltage regulating coil 21 adopts a double-layer multi-helix winding process, which is divided into an inner medium voltage regulating coil section 211 and an outer medium voltage regulating coil section 212. The double-layer structure is matched to the medium voltage side voltage regulation condition. All the leads are led out from the bottom to form an inverted U-shaped layout, which facilitates the neat arrangement of the leads and avoids the crossover and confusion of the leads. At the same time, it is easy to accurately connect with the medium voltage on-load tap changer 5.

[0027] The series coil 12 is composed of an upper series coil segment 121 and a lower series coil segment 122 connected in parallel, and the whole adopts an inner-screen continuous winding process. The upper series coil segment 121 and the lower series coil segment 122 are completely symmetrical in structure and have opposite winding directions, which can ensure accurate impedance matching and balanced and stable operation of the two coil segments, reduce the operating failure caused by impedance imbalance from the source, and improve the voltage regulation stability of the high-voltage winding 1 and the overall operational reliability of the equipment.

[0028] like Figure 5 As shown, taking phase A as an example, the lead wires of series coil 12 and common coil 11 are connected to the corresponding voltage regulating switch according to the established electrical logic to ensure accurate wiring logic and reliable connection.

[0029] The selection and layout of the voltage regulating switch are adapted to the winding structure design. The high-voltage winding 1 is equipped with a single-bridge bridging type non-excitation voltage regulating tap changer, specifically divided into a two-phase high-voltage non-excitation voltage regulating tap changer 6 adapted to phases A and B, and a single-phase high-voltage non-excitation voltage regulating tap changer 7 adapted to phase C. For example... Figure 7 As shown, the high-voltage non-excitation tap changer completes the tap position switching and bridging operations according to the predetermined operating logic. Figure 7 The operating principle and switching process of the high-voltage tap changer are clearly explained to ensure accurate voltage regulation and safe and reliable electrical switching. The high-voltage two-phase de-energized tap changer 6 and the high-voltage one-phase de-energized tap changer 7 are installed independently by phase and operate in a coordinated manner by phase, which is highly matched with the three-phase operating electrical characteristics of the transformer.

[0030] Medium-voltage winding 2 is equipped with a medium-voltage on-load tap changer 5, the specifications of which are matched with the number of phases and insulation class of medium-voltage winding 2. For example... Figure 4As shown, the low-voltage winding 3 is equipped with a low-voltage on-load tap changer 4. The specifications of this switch are matched with the number of phases and insulation class of the low-voltage winding 3. Figure 4 This visually demonstrates the connection structure between the outlets of low-voltage coil 31 and low-voltage coil 32 and the low-voltage on-load tap changer 4. For example... Figure 6 As shown, all voltage regulating switches are neatly arranged and clearly zoned. The high-voltage two-phase no-excitation voltage regulating tap changer 6, the high-voltage one-phase no-excitation voltage regulating tap changer 7, the medium-voltage on-load voltage regulating tap changer 5, and the low-voltage on-load voltage regulating tap changer 4 are all highly compatible with the voltage regulating taps and voltage regulating modes of their corresponding windings, ensuring smooth execution of voltage regulating operations and precise switching of voltage regulating positions for each winding.

[0031] In addition, multi-winding transformers with voltage regulation can preset fixed connection groups according to actual application requirements. The low-voltage winding 3 is connected according to the design phase through phase-to-phase leads to realize the preset connection group, further ensuring the overall wiring standardization and stable and reliable operation of the transformer.

[0032] This invention also discloses a method for preparing the above-mentioned multi-winding transformer with adjustable voltage, specifically including the following steps: S1. Prepare a three-phase five-column iron core and perform standardized insulation pretreatment on the iron core columns. According to the predetermined winding arrangement from the inside to the outside, wind low-voltage coil 31, low-voltage coil 32, common coil 11, medium-voltage coil 21 and series coil 12 in sequence on the iron core columns. Perform interlayer insulation treatment on each group of coils and reserve the corresponding exits of each group of coils simultaneously. When winding the series coil 12, adopt a segmented synchronous winding process, wind the upper series coil segment 121 and the lower series coil segment 122 separately. After the winding is completed, first pre-connect the two coil segments in parallel, and then uniformly implement interlayer insulation treatment to ensure that the upper series coil segment 121 and the lower series coil segment 122 have impedance matching and opposite winding directions.

[0033] S2. Precisely connect the common coil 11 and the series coil 12 to form the high-voltage winding 1, and at the same time make the high-voltage winding 1 and the medium-voltage winding 2 form a stable self-coupling connection. At the preset voltage adjustment points at the end of the series coil 12, the beginning of the common coil 11, the end of the common coil 11, and the end of the low-voltage coil 31, respectively, accurately lead out voltage adjustment taps and conventional terminals, and perform special insulation protection on all voltage adjustment taps. When the high-voltage winding 1 and the medium-voltage winding 2 are self-coupling connected, the end of the common coil 11 is used as the common neutral point for positioning wiring. After the wiring is completed, the common neutral point is treated with double-layer insulation and sealing to enhance the insulation protection performance of the neutral point.

[0034] S3. Connect the voltage regulating taps of high-voltage winding 1 to the corresponding high-voltage off-load voltage regulating tap changer, using a single-bridge bridging connection method. Connect the voltage regulating taps of phase A and phase B to the high-voltage two-phase off-load voltage regulating tap changer 6, and connect the voltage regulating tap of phase C to the high-voltage one-phase off-load voltage regulating tap changer 7. Connect the voltage regulating taps of medium-voltage winding 2 to the corresponding medium-voltage on-load voltage regulating tap changer 5, and connect the voltage regulating taps of low-voltage winding 3 to the corresponding low-voltage on-load voltage regulating tap changer 4. All types of switches are connected according to the number of phases to ensure accurate wiring.

[0035] S4. Complete the standard lead wire connection between the corresponding outputs of low voltage coil 31, low voltage coil 32, common coil 11, medium voltage regulating coil 21, series coil 12, various voltage regulating switches and external bushings, reserve sufficient electrical insulation distance according to the established insulation level requirements, and perform all-round insulation wrapping on all exposed connection points and leads to completely eliminate insulation hazards.

[0036] S5. Assemble the transformer body after wiring is completed. After assembly, conduct special tests on overall voltage regulation performance and insulation performance, focusing on verifying the independent working reliability of the high voltage regulation unit, medium voltage regulation unit and low voltage regulation unit to ensure that the finished product fully meets the design requirements.

[0037] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A multi-winding transformer with adjustable voltage, characterized in that, It includes a three-phase five-limb iron core, a high-voltage winding, a medium-voltage winding, and a low-voltage winding; the low-voltage winding consists of a low-voltage coil and a low-voltage adjustment coil; the high-voltage winding consists of a common coil and a series coil; the medium-voltage winding includes a medium-voltage adjustment coil and a common coil; the low-voltage coil, the low-voltage adjustment coil, the common coil, the medium-voltage adjustment coil, and the series coil are wound and arranged sequentially from the inside to the outside on the iron columns of the three-phase five-limb iron core; The high-voltage winding and the medium-voltage winding form a self-coupling connection; The high-voltage winding, the medium-voltage winding, and the low-voltage winding are each equipped with an independent voltage regulating unit; The high-voltage winding adopts a single-bridge bridging constant flux no-excitation voltage regulation, and does not have an independent high voltage regulation coil. The voltage regulation tap is directly opened and led out to the off-end position of the series coil. Both the medium-voltage winding and the low-voltage winding adopt on-load voltage regulation with constant flux in both directions; the voltage regulation point of the medium-voltage winding is set between the beginning of the common coil and the end of the series coil; the end of the common coil serves as the common neutral point shared by the high-voltage winding and the medium-voltage winding. The low-voltage winding has a fully insulated structure, and its voltage adjustment point is located at the end of the low-voltage coil. The high-voltage winding is equipped with an off-excitation voltage regulating tap changer; the medium-voltage winding and the low-voltage winding are respectively equipped with on-load tap changers adapted to their own number of phases.

2. The multi-winding transformer with adjustable voltage according to claim 1, characterized in that, The low-voltage coil is continuously wound with the first end protruding upwards and the last end protruding downwards to achieve multi-stage tapping.

3. The multi-winding transformer with adjustable voltage according to claim 2, characterized in that, The common coil is continuously wound with the first end protruding at the top and the last end protruding at the bottom; the intermediate voltage regulating coil is wound with double-layer multi-helix winding, and all protrusions are led out from the bottom to form an inverted U-shaped structure.

4. The multi-winding transformer with adjustable voltage according to claim 3, characterized in that, The series coil is composed of an upper series coil segment and a lower series coil segment connected in parallel, and is wound continuously with an inner screen; the upper series coil segment and the lower series coil segment are symmetrical in structure and have opposite winding directions.

5. The multi-winding transformer with adjustable voltage according to claim 1, characterized in that, The non-excitation voltage regulating tap changer has a single-bridge bridging structure, including a two-phase switch adapted to phases A and B, and a single-phase switch adapted to phase C.

6. The multi-winding transformer with adjustable voltage according to claim 1, characterized in that, The transformer is provided with a preset connection group; the low-voltage winding is connected by phase-to-phase leads to realize the preset connection group.

7. A method for manufacturing a multi-winding transformer with adjustable voltage as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Prepare a three-phase five-column iron core and perform insulation pretreatment on its iron core columns; according to the arrangement order from the inside to the outside, wind low-voltage coil, low-voltage coil, common coil, medium-voltage regulating coil and series coil in sequence on the iron core columns, and perform interlayer insulation treatment on low-voltage coil, low-voltage coil, common coil, medium-voltage regulating coil and series coil respectively, and simultaneously reserve the corresponding output of low-voltage coil, low-voltage coil, common coil, medium-voltage regulating coil and series coil; S2. Connect the common coil and the series coil to form a high-voltage winding, and make the high-voltage winding and the medium-voltage winding form an autotransformer connection; at the preset voltage adjustment points at the end of the series coil, the beginning of the common coil, the end of the common coil, and the end of the low-voltage coil, respectively, lead out voltage adjustment taps and conventional terminals, and provide insulation protection for the voltage adjustment taps. S3. Connect the voltage regulating tap of the high voltage winding to the corresponding off-load voltage regulating tap changer, and connect the voltage regulating taps of the medium voltage winding and low voltage winding to the corresponding on-load tap changers of the corresponding phase number. S4. Complete the lead wire connection between the low voltage coil, low voltage coil, common coil, medium voltage regulating coil, series coil, voltage regulating switch and external bushing, reserve electrical insulation distance according to insulation level requirements, and insulate all exposed connection points and leads. S5. Assemble the transformer body after wiring is completed, and then conduct overall voltage regulation and insulation performance tests to verify the independent working reliability of the high voltage regulating unit, medium voltage regulating unit, and low voltage regulating unit.

8. The preparation method according to claim 7, characterized in that, In step S1, the series coil is wound using a segmented synchronous winding process, with the upper series coil segment and the lower series coil segment wound separately. After winding, the upper and lower series coil segments are pre-connected in parallel, and then interlayer insulation is uniformly implemented to make the upper and lower series coil segments impedance matched and their winding directions opposite.

9. The preparation method according to claim 7, characterized in that, In step S2, when the high-voltage winding and the medium-voltage winding are self-coupled, the common coil end is used as the common neutral point for positioning wiring. After the wiring is completed, the neutral point is treated with double-layer insulation and sealing. In step S3, the high-voltage regulating tap and the non-excitation regulating tap changer are connected by a bridging connection.

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