Epoxy pouring multi-pulse phase-shifting transformer and design method thereof

Abstract

The invention discloses an epoxy pouring multi-pulse phase-shifting transformer and a design method thereof, and belongs to the field of frequency conversion. By adopting an epoxy pouring structure and an accurate phase-shifting adjusting technology, the multi-pulse phase-shifting transformer disclosed by the invention has the characteristics of efficient voltage regulation and low harmonic wave, the stability, efficiency and safety of the transformer can be remarkably improved, and the multi-pulse phase-shifting transformer is widely applicable to industrial equipment, variable-frequency driving and high-power electric power systems which need accurate electric energy regulation and control.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of frequency conversion, and in particular to an epoxy cast multi-pulse phase-shifting transformer and a design method thereof. Background Art

[0002] Multi-pulse phase-shifting transformers are core components in the frequency conversion field and are widely used in AC-DC conversion systems. Typical specifications include 18-pulse, 24-pulse, 36-pulse and 48-pulse. Traditional phase-shifting transformers usually use Nomex paper as the conductor insulation material, and the whole is varnished and non-encapsulated. However, this design is susceptible to moisture in high humidity or harsh environments, resulting in reduced insulation performance. In addition, traditional products lack rigid support between high and low voltage windings, and their short-circuit resistance is insufficient, which affects operational stability.

[0003] The epoxy casting technology was introduced in the relevant technology, which provided a new direction for improving the reliability of the phase-shifting transformer. By encapsulating and casting the windings with epoxy resin, the insulation performance can be significantly enhanced and the environmental adaptability can be improved. However, in the design of multi-pulse phase-shifting transformers, due to the large number of terminals on the low-voltage side and the complex structure, there are great challenges in wire winding and terminal arrangement. Especially under the conditions of high-density wiring, the traditional layout method is prone to insufficient terminal row space and complicated wiring. Therefore, in view of the above-mentioned technical difficulties, it is particularly important to improve the number of turns selection, wire arrangement and terminal arrangement. Taking a single 48-pulse phase-shifting transformer as an example, this application proposes a targeted improvement plan to solve the above-mentioned difficulties and improve product performance. Summary of the invention

[0004] The present application provides an epoxy cast multi-pulse phase-shifting transformer and a design method thereof. The application is as follows:

[0005] According to one aspect of the present application, an epoxy cast multi-pulse phase-shifting transformer is provided, and the epoxy cast multi-pulse phase-shifting transformer comprises:

[0006] An iron core, located at the center of the transformer body, for supporting the high voltage winding and the low voltage winding and providing a magnetic flux magnetic circuit;

[0007] The high voltage winding is located in the inner layer of the core and is used for input voltage conversion tasks;

[0008] The low voltage winding is located outside the high voltage winding and is used to adjust the phase shift angle according to the phase shift principle;

[0009] Lead terminals and terminal blocks, the lead terminals are fixedly connected to the terminal blocks by welding or nuts, the lead terminals are used to connect the high-voltage winding, the low-voltage winding and the lead terminals, and the lead terminals are also led out to an external circuit through the terminal blocks;

[0010] Copper nuts, each winding is connected to the terminal block through the copper nuts.

[0011] Optionally, the core adopts a five-level stacked iron design;

[0012] The distance between the iron core and the high-voltage winding meets the requirements of power frequency withstand voltage and lightning impulse voltage.

[0013] Optionally, the high voltage winding adopts a single spiral winding and a segmented cylinder structure design;

[0014] The number of turns of the high-voltage winding is designed to be tapped at ±5%, and the number of turns ranges from 476 to 431 turns, wherein the tap terminal is located at the upper end or the lower end of the high-voltage winding, and multi-gear switching is achieved through the tap terminal, and the high-voltage winding supports a ±5% voltage regulation function.

[0015] Optionally, the low voltage winding is of epoxy casting design;

[0016] Each phase winding of the low-voltage winding is divided into 4 groups; the first three groups of each phase winding are main power supply groups for phase shifting function, wherein each group of each phase winding includes 8 phase-shifting windings and 8 main windings, the tail end of the phase-shifting winding is directly connected to the head end of the corresponding main winding to form a continuous current path, the phase-shifting winding is used to adjust the angle, the main winding and the phase-shifting winding are used together for power transmission, and the fourth group of each phase winding is an auxiliary winding for powering the fan and the thermostat.

[0017] Optionally, the terminal rows are arranged in a staggered manner.

[0018] On the other hand, a design method for an epoxy cast multi-pulse phase-shifting transformer is provided, the method being used for the epoxy cast multi-pulse phase-shifting transformer described above, the method comprising:

[0019] For core design,

[0020] The core is designed according to a five-level stacking and laminating type, and the five-level stacking and laminating type design meets the flux requirements of the transformer;

[0021] The distance between the iron core and the high-voltage winding is determined according to the power frequency withstand voltage and lightning impulse voltage requirements.

[0022] Optionally, the method further includes:

[0023] For high voltage winding design,

[0024] Calculating the rated number of turns of the high voltage winding according to the input voltage;

[0025] Divide the subsequent turns according to the ±5% tapping position and mark them as +5%, rated, and -5% respectively;

[0026] The main body of the high-voltage winding is designed using a single spiral winding and a segmented cylinder structure;

[0027] The tap terminal is arranged at the upper end or the lower end of the high-voltage winding and is connected to the terminal block through the copper nut to realize the tap adjustment function.

[0028] Optionally, the method further includes:

[0029] For low voltage winding design,

[0030] Dividing the low voltage winding into four groups;

[0031] The first three groups are designed as the main power supply groups, each group contains 8 phase-shifting windings and 8 main windings, and the phase-shifting windings and the main windings are connected end to end to form a continuous current path;

[0032] Designing the fourth group as the auxiliary winding;

[0033] Arranging the phase-shifting windings in sequence according to the phase-shifting angles;

[0034] The main winding and the phase-shift winding are connected and arranged in sequence according to the phase-shift angle.

[0035] Optionally, the method further includes:

[0036] For lead and terminal block design,

[0037] The lead terminals of the high voltage winding and the low voltage winding are fixedly connected to the terminal block by welding or nuts;

[0038] Connecting the tail end of the phase-shift winding and the head end of the main winding via a common lead terminal;

[0039] The terminal rows are arranged in a staggered manner.

[0040] Optionally, the method further includes:

[0041] The coils of the low-voltage winding and the high-voltage winding are cast and fixed.

[0042] In an embodiment of the present application, an epoxy cast multi-pulse phase-shifting transformer is provided, which is particularly suitable for the frequency conversion field. The epoxy cast multi-pulse phase-shifting transformer is superior to the traditional transformer design in many aspects, especially in voltage regulation accuracy, mechanical strength and system stability, as shown below.

[0043] Improved voltage regulation accuracy: The transformer is designed with a ±5% voltage regulation function. By switching the tap terminals, it can cope with different grid voltage fluctuations and ensure a stable output voltage, thereby improving the reliability and adaptability of the system. Accurate phase shift angle adjustment: By accurately adjusting the number of turns of the phase shift winding, the phase angle of the voltage can be effectively adjusted to ensure that the phase shift angle error of the output voltage is less than 0.5°. This reduces the interference and pollution of the frequency conversion system to the grid voltage, and high-order harmonics can be offset by the characteristics of the transformer itself. High reliability and durability: The epoxy casting design significantly improves the insulation performance and short-circuit resistance of the transformer. This design can effectively prevent the aging of traditional winding insulation materials due to moisture or harsh environment, and ensure the long-term stable operation of the transformer under high load conditions. Compact and efficient design: Through the staggered terminal block design and optimized winding layout, the overall structure of the transformer is more compact and the electrical connection is more stable. This not only improves the space utilization of the terminal block, but also reduces the mutual interference of the wire arrangement, and improves the operational reliability of the system. Enhanced short-circuit performance: The design of epoxy casting and rigid support enables the transformer to withstand higher electrical stress, enhances the anti-interference ability to short-circuit conditions, and improves the safety and reliability of the transformer when a fault occurs. 48-pulse rectification optimization: In the design of the low-voltage winding, the combination of the phase-shifting winding and the main winding enables the transformer to achieve a 48-pulse rectification function, reducing the harmonic content of the current and improving the conversion quality of electric energy. This design is widely used in high-power systems that require a stable DC power supply and high-power systems that require AC-DC-AC conversion. Wide applicability: The transformer is highly flexible and configurable, and can be adjusted according to different working conditions (such as grid voltage fluctuations, load demand, etc.), and is suitable for multiple fields such as industry, renewable energy, and efficient power transmission. Reduced maintenance costs: Since the design of the outlet terminals of the high-voltage winding and the low-voltage winding is easy to connect and replace, maintenance work becomes easier, greatly reducing the maintenance cost and downtime of the transformer. To sum up, by adopting epoxy casting structure and precise phase shifting regulation technology, the multi-pulse phase shifting transformer of the present application has efficient voltage regulation and low harmonic characteristics, which can significantly improve the stability, efficiency and safety of the transformer, and is widely used in industrial equipment, variable frequency drives and high-power power systems that require precise power control. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 FIG. 2 is a schematic diagram of the arrangement of low-voltage windings provided by an exemplary embodiment of the present application; FIG. 3 is a diagram of the phase shift angle vector relationship and lead connection of each group provided by an exemplary embodiment of the present application; Figure 3 It is the working principle diagram of multi-pulse phase-shifting transformer, frequency converter and variable frequency motor; Figure 4 It is a schematic diagram of the inverter output terminals of each group being connected in series to form a three-phase power supply; Figure 5It is a schematic diagram of the connection between the outlet terminal and the outlet panel after the multi-pulse transformer is cast; Figure 6 The diagram shows the relative positions of transformer windings and core; Figure 7 A schematic diagram of the high voltage winding winding method is shown; Figure 8 The figure shows the schematic diagram of the coil outlet terminal on the high voltage winding side; Fig. 9 The figure shows the schematic diagram of the turns distribution on the low voltage winding side; Fig.10 Shown is a schematic diagram of the arrangement of turns of the low voltage winding; Fig.11 The figure shows a schematic diagram of winding in a multi-section cylindrical winding method; Fig.12 Shown is a schematic diagram of the designed component 3111; Fig.13 Shown is a schematic diagram of the arrangement of parts 3111; Fig.14 The figure shows the location of the lead wires of the low voltage winding side terminals; Fig.15 The terminal block diagram on the low voltage winding side is shown; Fig.16 The diagram shows the copper nut of the low voltage winding side terminal; Fig.17 The figure shows the schematic diagram of the outlet position of the high voltage winding; Fig.18 Shown is the corresponding Fig.17 Schematic diagram of the P-direction outgoing line position; Fig.19 The figure shows the location of the lead-out terminal block on the low-voltage winding side; Fig. 20 Shown is a schematic diagram of the outgoing line position of the fourth largest group on the low-voltage winding side. DETAILED DESCRIPTION

[0045] To make the purpose, application and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0046] The term "multiple" as used herein refers to two or more than two. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the related objects are in an "or" relationship.

[0047] First, the main technical parameters of the epoxy cast multi-pulse phase-shifting transformer are explained, including the transformer capacity, input voltage, tap position and operating frequency.

[0048] The capacity of the transformer is 1000kVA (kilovolt-ampere), which indicates the apparent capacity of the transformer, that is, the apparent capacity of the transformer is 1000 kVA. This value determines the maximum load power that the transformer can withstand. The input voltage of the high-voltage winding (primary side) of the transformer is 10 kV. In other words, the transformer is designed to receive a voltage of 10kV and convert it into an output voltage on the low-voltage side, where 10kV is a typical grid voltage level used in larger-scale substations or industrial power supply systems. The high-voltage winding (primary side) has a tapping function, allowing the input voltage (high-voltage side voltage) of the transformer to be adjusted through different tapping terminals. The tapping position ±5% means that the adjustment range of +5% and -5% indicates that the input voltage of the transformer can be adjusted by ±5% on the basis of 10kV, that is, it can be adjusted to 10.5kV (+5%) or 9.5kV (-5%). This can adapt to grid voltage fluctuations and ensure that the transformer can work normally according to different grid input voltage conditions. The operating frequency of the transformer is 50Hz, which means that the transformer is designed for 50 Hertz (Hz) AC power systems. 50Hz is the standard power frequency in most parts of the world (including Europe, Asia, etc.). Frequency affects the rate of change of electromagnetic waves, and the design of the transformer needs to ensure stable operation at 50Hz.

[0049] Example 1

[0050] The present application provides an epoxy cast multi-pulse phase-shifting transformer, wherein the epoxy cast multi-pulse phase-shifting transformer includes an iron core, a high-voltage winding, a low-voltage winding, lead terminals, a terminal block and copper nuts. The present application will describe each structure.

[0051] 1. The core is located in the center of the transformer body, which is used to support the high-voltage winding and the low-voltage winding and provide the magnetic flux circuit. The core adopts a five-level stacked iron design, and the distance between the core and the high-voltage winding meets the requirements of power frequency withstand voltage and lightning impulse voltage.

[0052] Second, the high-voltage winding is located in the inner layer of the core and is used for input voltage conversion tasks. Among them, the high-voltage winding adopts a single spiral winding and a segmented cylindrical structure design. The number of turns of the high-voltage winding is designed to be ±5% tapped, and the number of turns ranges from 476 to 431 turns. Among them, the tap terminal is located at the upper or lower end of the high-voltage winding. The tap terminal is used to realize multi-gear switching. The high-voltage winding supports ±5% voltage regulation function. The following further describes the relationship between the high-voltage winding and the tap terminal.

[0053] The tap terminal is a key component in the design of high-voltage windings, which is used to adjust the number of turns to achieve the ±5% adjustment function of the input voltage. The tap terminals are mainly distributed at the head and tail ends of the high-voltage winding, and are connected to different turns of the winding through wires. The number of turns of the high-voltage winding ranges from 476 to 431 turns, which is divided into three gears according to the ±5% voltage adjustment requirements. +5% gear: the high-voltage winding has the most turns, which is 476 turns; rated gear: the high-voltage winding has 454 turns; -5% gear: the high-voltage winding has the least turns, which is 431 turns. The tap terminals of the high-voltage winding are arranged at the upper or lower end of the winding, including the following.

[0054] The high-voltage winding head terminal (such as A / B / C terminal) is used to lead out the initial voltage of the high-voltage winding. The high-voltage winding end tapping terminal (such as X1 / Y1 / Z1, X2 / Y2 / Z2, X3 / Y3 / Z3). Among them, the X1 / Y1 / Z1 terminal is used as the +5% gear terminal, connected to the outermost turn of the winding; the X2 / Y2 / Z2 terminal is used as the rated gear terminal, connected to the middle turn of the winding; the X3 / Y3 / Z3 terminal is used as the -5% gear terminal, connected to the innermost turn of the winding.

[0055] Adjustment principle of the tap terminal. The tap terminal is connected to different turns by switching the wire to achieve voltage regulation. For example, when connected to the +5% gear terminal (X1 / Y1 / Z1), the number of turns is 476 turns, and the output voltage is increased. When connected to the rated gear terminal (X2 / Y2 / Z2), the number of turns is 454 turns, and the output voltage is rated. When connected to the -5% gear terminal (X3 / Y3 / Z3), the number of turns is 431 turns, and the output voltage is reduced. In the actual layout, the tap terminal is fixed to the terminal board by a copper nut, which is convenient for external operators to adjust the connection position to switch the gear. All tap terminals have clearly marked turns positions and corresponding gear information to reduce the risk of misoperation. Through the above-described connection method of the tap terminal and the high-voltage winding, the requirements of different input grid voltages can be effectively met, while ensuring the stability and adaptability of the voltage output. This design provides strong support for the flexibility and applicability of the transformer.

[0056] 3. The low voltage winding is located outside the high voltage winding and is used to adjust the phase shift angle according to the phase shift principle.

[0057] The low voltage winding is designed for epoxy casting. After epoxy resin casting, all leads and terminal blocks are fixed in the resin, which improves the insulation performance and short circuit resistance of the overall structure. The casting process also prevents the lead from moving or wearing during operation.

[0058] Each phase winding of the low-voltage winding is divided into 4 groups. The first three groups of each phase winding are the main power supply groups for phase shifting function. Each group of each phase winding contains 8 phase shifting windings and 8 main windings. The fourth group of each phase winding is an auxiliary winding for powering the fan and thermostat. Figure 1 In the low-voltage winding arrangement diagram shown, the left side is the primary side, i.e., the high-voltage winding, and the right side is the secondary side, i.e., the low-voltage winding. In the low-voltage winding, as shown above, each phase winding of the low-voltage winding is divided into 4 groups, and the first three groups of each phase winding (represented by group 1, group 2, and group 3) are the main power supply groups for the phase shift function, wherein each group of each phase winding contains 8 phase-shifting windings (represented by windings 1 to windings n) and 8 main windings (shown in the figure on the left side of windings 1 to windings n), and the fourth group of each phase winding (represented by group 4) is an independent 220V auxiliary winding for powering the fan and the thermostat.

[0059] The phase-shift winding is used to adjust the angle. By changing the number of winding turns and the current phase, it is responsible for adjusting the phase-shift angle of the voltage (for example, -26.25° to +26.25°, etc.) to ensure the phase-shift accuracy of the output voltage. The phase angles of the phase-shift windings in the 8 phase-shift windings differ by 7.5° and are arranged from -26.25° to +26.25°. As a result, the design ensures the accuracy of the phase-shift angle deviation (≤0.5°), optimizes the balance between the voltage ratio and the phase-shift angle, and gives priority to voltage accuracy when the voltage ratio and the phase-shift angle cannot be accurately controlled at the same time.

[0060] The main winding and the phase-shift winding are used together for power transmission, transferring the current generated by the phase-shift winding to the inverter. In each group, the tail end of the phase-shift winding is directly connected to the head end of the corresponding main winding to form a continuous current path, realizing the phase-shift angle adjustment function of the low-voltage winding while maintaining the stability of power transmission. For example, the tail end of the -26.25° phase-shift winding is connected to the head end of the corresponding main winding, the tail end of the -18.75° phase-shift winding is connected to the head end of the corresponding main winding, and so on.

[0061] The fourth group of each phase winding is an auxiliary winding used to power the fan and thermostat. It works independently and does not participate in the phase shift function. It is specifically used to provide power for the transformer's fan and thermostat control systems. The capacity of this auxiliary winding is 3kVA, providing a stable 220V power supply for the system.

[0062] Taking a 48-pulse phase-shifting transformer as an example, the secondary side (low-voltage winding) has a total of 75 windings, of which 72 windings are used for phase shifting and power transmission of the main power supply, and 3 windings are independent auxiliary windings, which jointly support the normal operation of the transformer and the power supply of auxiliary equipment.

[0063] It should be noted that when the transformer is in the no-load state, the voltage output by the transformer low-voltage winding (secondary side) is 690V. That is, in the no-load state, the rated output voltage of the transformer is 690V. When the transformer is connected to the load, the output voltage may drop, but after the AC-DC-AC conversion of the inverter, the output end can provide the frequency and voltage required by the load motor. This working mode is suitable for higher-power electrical equipment, such as high-power variable-frequency motors, industrial machines, etc.

[0064] For the specific layout, in each group of 8 windings, the phase-shift winding and the main winding are arranged alternately, and the phase-shift winding is close to the main winding, arranged layer by layer to ensure a compact structure. Each group of windings can be wound uniformly in a clockwise or counterclockwise manner.

[0065] In addition, the phase-shift winding of the present application realizes phase-shift angle adjustment for 48-pulse rectification function. The main winding and the phase-shift winding work together to complete the low-voltage output, ensure that the output voltage meets the rectification requirements, complete the power transmission on the low-voltage side, and through the angle adjustment of the phase-shift winding, the phase-shifted current is introduced into the rectifier bridge to achieve accurate 48-pulse rectification. The combination of the phase-shift winding and the main winding constitutes the functional unit of the low-voltage winding, which directly determines the phase-shift accuracy and voltage stability of the transformer.

[0066] As shown in Figure 2, the phase shift angle vector relationship and lead connection diagram of each group are shown. The phase shift angle is changed by adjusting the connecting leads and the number of turns, and then passes through the IBGT rectifier bridge to form 48-pulse rectification. In each group of 8 phase-shift windings, the phase angles of the phase-shift windings from -26.25° to +26.25° differ by 7.5°.

[0067] For the marks in Figure 2, a1-a8 represent the serial number of the windings in each of the three groups. For example, a1b1c1 is the first group. The position presented in the figure is the change in the relative position relationship after the phase shift. From the figure, we can clearly see that the synthetic vector diagram of the three phases a1b1c1 and the synthetic vector diagram of the three phases a2b2c2 differ by 7.5°. This is the vector representation. If it is replaced with a sine representation, it means that within a cycle 2Π, the time is equally divided into 48 parts, and these sine curves each occupy Π / 24 of the time. Each winding is connected to the rectifier through the terminal block to provide it with a stable power input.

[0068] 4. Lead terminals and terminal blocks. Lead terminals are fixedly connected to terminal blocks by welding or nuts. Lead terminals are used to connect high-voltage windings, low-voltage windings and lead terminals. Lead terminals are also led out to external circuits through terminal blocks.

[0069] Among them, the terminal row is arranged in a staggered manner. In the staggered arrangement of the terminal row, since each phase-shifting winding and the main winding of the low-voltage winding need to lead out multiple terminals, the number of terminals is large, and the traditional arrangement method will lead to dense terminals and complex wiring. To solve this problem, the terminal row is arranged in a staggered manner, that is, the head and tail terminals of the same winding group are distributed in different columns of the terminal row. The terminals of two adjacent winding groups are staggered on the terminal row to avoid the adjacent terminals being too close. The staggered arrangement design is combined with the epoxy casting structure to simplify the layout of the outgoing wires. Specifically, the lead terminal is a component that connects the winding and the terminal row, and is finally led out to the external circuit through the terminal row. The lead terminal is fixed to the terminal row by welding or nuts to ensure that the outgoing wires of each winding group are clear and independent. Among them, the staggered arrangement is aimed at the arrangement of the terminals on the terminal row, with the purpose of optimizing space utilization and reducing interference between adjacent terminals. The role of the staggered arrangement is as follows. Improve the space utilization of the terminal row and avoid wiring overlap caused by a large number of terminals. Reduce wiring interference between adjacent terminals and improve the operating reliability of the system. Provide more space for lead arrangement and facilitate lead welding and fixation.

[0070] In addition, the outgoing line layout is simplified, and the specific process is provided as follows. The tail end of the phase-shifting winding of each set of low-voltage windings is connected to the head end of the main winding through a copper nut to form a common lead-out point; the lead wire is directly connected to the corresponding terminal row from the outgoing line position of the winding, reducing unnecessary intermediate links; the number of turns at the head and end of the high-voltage winding is designed according to the tapping gear, and is directly connected to the corresponding terminal of the high-voltage terminal row through a copper nut. Then the layout of the terminal row is optimized. Specifically, according to the relationship between the number of turns of the phase-shifting winding and the main winding, a special terminal row layout scheme is designed. The lead terminal is fixedly connected to the terminal row by welding or nuts to ensure that the outgoing line of each set of windings is clear and independent. The staggered terminal rows reduce the distance requirements between the terminals, making the overall structure of the terminal row more compact. At the same time, it avoids the wiring confusion caused by the excessive density of terminals in traditional terminal rows.

[0071] 5. Copper nuts. Each winding is connected to the terminal block through copper nuts.

[0072] Example 2

[0073] On the other hand, a design method for an epoxy cast multi-pulse phase-shifting transformer is provided, and the method is used for the above-mentioned epoxy cast multi-pulse phase-shifting transformer.

[0074] For the core design, the core is designed according to the five-level stacking iron type, which meets the transformer flux requirements; the distance between the core and the high-voltage winding is determined according to the power frequency withstand voltage and lightning impulse voltage requirements. For the high-voltage winding design, the rated number of turns of the high-voltage winding is calculated according to the input voltage; the subsequent number of turns is divided according to the ±5% tapping gear, and marked as +5%, rated, and -5% respectively; the body of the high-voltage winding is designed using a single spiral winding and a segmented cylindrical structure; a tap terminal is set at the upper or lower end of the high-voltage winding, and connected to the terminal block through a copper nut to realize the tap adjustment function. The specific process is as follows.

[0075] For high-voltage winding design, the initial number of turns must first be calculated based on the input voltage of the transformer, and then the final number of turns must be determined based on voltage accuracy, phase shift angle, and other related factors. Based on previous engineering experience, the initial number of turns (rated gear) of winding 4 can be set to 18 turns, and the number of turns of the high-voltage winding can be further determined by calculating the turn potential.

[0076] (1) Calculate the turn potential. According to the setting of the initial number of turns (rated gear) of winding 4 as 18 turns, its turn potential can be calculated:

[0077]

[0078] (2) Calculation of the number of turns on the input side. The input voltage is 10kV, and a Y connection is used. Using the above turn potential, the number of turns on the input side can be calculated:

[0079]

[0080] (3) Calculation of output side turns. The output side voltage is 690V, and the Δ connection method with phase-shifted winding is adopted. The number of turns on the output side can be calculated using the trigonometric function relationship. For example, taking -3.75° as an example, the phase shift angle is adjusted as follows.

[0081] Number of turns of phase-shift winding:

[0082]

[0083] Number of turns of main winding:

[0084]

[0085] Verification of turns and phase shift angle: Through the above calculation steps, the turns of each group of phase shift windings and the main winding of the low-voltage winding can be obtained. Based on these data, further verification of the phase shift angle and transformation ratio is performed. If there is a conflict between the phase shift angle and the voltage transformation ratio, adjustment is made according to the principle of voltage accuracy first.

[0086] For the low-voltage winding design, the low-voltage winding is divided into four groups; the first three groups are designed as the main power supply groups, each group contains 8 phase-shifting windings and 8 main windings, and the phase-shifting windings are connected end to end with the main windings to form a continuous current path; the fourth group is designed as an auxiliary winding; the phase-shifting windings are arranged in sequence according to the phase-shifting angle; the main windings are connected to the phase-shifting windings, and arranged in sequence according to the phase-shifting angle.

[0087] Table 1 shows the number of turns of the phase-shift winding and the main winding, the phase-shift angle deviation and the ratio deviation after vector synthesis at different phase-shift angles of the low-voltage winding. According to the calculation results, it can be seen that different turns configurations have different effects on the accuracy of the voltage ratio and the phase-shift angle. In Table 1, each phase-shift angle (such as -3.75°, -11.25°, etc.) corresponds to a different number of turns of the phase-shift winding and the main winding. The value of the deviation after vector synthesis reflects the accuracy of the phase-shift angle and the ratio.

[0088] Table 1

[0089]

[0090]

[0091] After further iterative calculations, the turns configuration in Table 2 was finally selected as the standard parameters for this application. Through vector fitting and deviation verification, it was determined that the low-voltage winding 4 (referring to the rated gear of the fourth group of auxiliary windings in the low-voltage winding) took 17 turns, and the phase shift angle deviation and transformation ratio deviation were within a more precise range. These configurations optimize the performance of the transformer and ensure precise adjustment of the voltage ratio and phase shift angle. As shown in Table 2, through optimization, 454 turns were finally selected as the number of turns of the high-voltage winding, and the final turn potential was calculated to be 12.717V / turn:

[0092]

[0093] The phase shift angle deviation and transformation ratio deviation are more accurate than those in Table 1.

[0094] Table 2

[0095]

[0096]

[0097] By comparing Table 1 and Table 2, it can be clearly seen that the phase shift angle deviation and the transformation ratio deviation after vector synthesis in Table 2 are more accurate than those in Table 1, so the number of turns in Table 2 is selected as the design parameter.

[0098] After determining the number of turns of the product, the lead and terminal block design can be carried out. Since the low-voltage winding has more outlet terminals, the low-voltage winding can be distributed on the outermost side, and the high-voltage grid-side winding can be distributed on the inner side, close to the core. The distance from the high-voltage winding to the core must meet the product's power frequency withstand voltage and lightning impulse voltage. Figure 6 As shown, Figure 6 The relative position diagram of the transformer winding and the core is shown, wherein number 1 is the core, number 2 is the high-voltage winding side coil, and number 3 is the low-voltage winding side coil.

[0099] The high-voltage winding is located on the inner side of the transformer, close to the core. The initial rated gear turns are selected according to the input voltage of the transformer (10kV). The calculation of the initial rated gear turns is based on the initial setting of the rated gear of the low-voltage side winding 4. First, the rated gear turns of the low-voltage winding 4 are set to 18 turns, and then the final turns of the high-voltage winding are further determined based on relevant factors such as voltage accuracy and phase shift angle.

[0100] According to the set number of turns of the low-voltage winding 4 (18 turns), the turn potential of the high-voltage winding is calculated: The number of turns on the high-voltage side (474 ​​turns) is then calculated using the turn potential, and based on a comprehensive evaluation of relevant factors such as voltage accuracy and phase shift angle, the number of turns for the high-voltage rated position is ultimately determined to be 454 turns. This ensures that the high-voltage winding can adapt to an input voltage of 10kV and achieve ±5% voltage regulation through the tap terminals (i.e., the numbers of turns for the +5%, rated, and -5% positions are 476, 454, and 431 turns, respectively).

[0101] The high-voltage winding adopts a multi-section cylindrical structure and is wound in a spiral manner. The tap terminals are located at both ends of the high-voltage winding and are used to adjust the voltage. The tap terminals are fixed with copper nuts and connected to the external circuit through terminal blocks to ensure that the high-voltage winding can be adjusted according to the voltage fluctuations of the power grid.

[0102] In this embodiment, Figure 7 As shown, a schematic diagram of the high-voltage winding winding method is shown. 21 is the A / B / C terminal at the head end of the high-voltage winding side coil; 22 is the +5% tapping terminal at the end of the high-voltage winding side coil (X1 / Y1 / Z1); 23 is the rated gear terminal at the end of the high-voltage winding side coil (X2 / Y2 / C2); 24 is the -5% gear terminal at the end of the high-voltage winding side coil (X3 / Y3 / C3); Note, the first three sections are right-winding, and the last section is left-winding.

[0103] like Figure 8 The figure shows the schematic diagram of the high voltage winding side coil outlet terminal. When casting the transformer coil with epoxy casting, the bottom of the mold must be sealed because the resin mixture is in a viscous flow state (liquid state), otherwise the resin material will leak. Figure 7As can be seen in this example, the wires are led out at both ends of the coil, so it is necessary to make the lead-out terminals at the bottom of the mold. The first end lead-out terminal 21 has one for each phase winding, and the end lead-out terminals 22, 23, and 24 have one each, for a total of three. Therefore, it is more convenient to weld one lead-out terminal at the bottom of the mold and lead out the original wire at the other end. For details, please refer to Figure 8 It should be noted that the terminal 21 is at the bottom of the mold during casting, and the coil needs to be rotated 180° when it is cast.

[0104] like Fig. 9 The low voltage winding side turns distribution diagram shown in the figure, the low voltage winding adopts epoxy casting insulation, each phase consists of 4 groups, from the previous description, we know that the structure of group 1, group 2, group 3 is exactly the same, only group 1 and group 4 will be discussed. Specifically, Fig. 9 The diagram is a diagram of the turns distribution of group 1. 311-312, 321-322, 331-332, 341-342, 351-352, 361-362, 371-372, 381-382 are phase-shift windings, 312-313, 322-323, 332-333, 342-343, 352-353, 362-363, 372-373, 382-383 are main windings, connected into a triangle through external wiring. Fig. 9 It can be seen that the number of turns of Group 1 and Group 8, Group 2 and Group 7, Group 3 and Group 6, Group 4 and Group 5 are exactly the same, and the angle change is achieved only by the connection method of the external connection group. The current flowing through the phase-shifting coil is √3 times that of the main coil. In order to facilitate the arrangement and selection of the number of turns, the wire with the same thickness is selected. By adjusting the number of turns, the width of each layer and the total number of layers of each group of phase-shifting coils and the main coil are guaranteed to be consistent.

[0105] The number of turns of the low voltage winding is arranged as follows Fig.10 As shown in the figure, a group is also used as an example. Fig.10 This is the arrangement of the number of turns of the first group, all windings are right-handed. The second and third groups can be wound in the same way. Figure 3 The power frequency withstand voltage value between each large group is 16kV, and the distance between each large group is 36mm. The fourth large group is based on the technical agreement ±5% tapping, so the number of turns is 16-17-18, and it can be wound using a multi-section cylindrical winding method. Fig.11 .according to Fig.10 and Fig.11 , each group has a relatively small number of turns per layer. When the number of layers is large, there is a risk of conductor collapse. Therefore, component 3111 is designed, placed in the corresponding position, and wrapped with non-woven glass ribbon. Fig.12As shown, item 1 is an epoxy glass cloth plate, item 2 is a 0.2 mm thick electrical green shell paper, and 8 parts 3111 can be arranged along the circumferential direction, such as Fig.13 Schematic diagram of the arrangement of parts 3111 shown.

[0106] For lead and terminal block design, the lead terminals of high-voltage winding and low-voltage winding are connected to the terminal block by welding or nuts; the tail end of the phase-shifting winding and the head end of the main winding are connected by a common lead terminal; the terminal block is arranged in a staggered manner. The coils of the low-voltage winding and high-voltage winding are cast and fixed. The following diagram further explains. Fig.15 The figure shows the location of the lead wires of the low voltage winding side terminals. Furthermore, to facilitate the lead wire arrangement, the head terminals of two adjacent groups are arranged alternately. The terminal row diagram is shown in FIG. Fig.15 As shown, Fig.15 This is the terminal row diagram on the low voltage winding side.

[0107] Since there are many winding outlet terminals, the terminals on the terminal board are arranged in a staggered manner. Fig.10 The tail end of the phase-shifting coil and the head end of the main coil are connected. The two wires can be welded together on the copper nut of the common outlet terminal to facilitate the lead-in. In this way, all wires can be led out to the terminal block. Since the terminal block has a large number of terminals, if the traditional copper nut arrangement is used, the terminal block space is insufficient and the lead-out terminals cannot be arranged. Therefore, this example also designs a terminal, such as Fig.16 shown. Fig.16 A schematic diagram of the copper nut for the low-voltage winding terminal is provided. The copper nut is divided into two parts, the lower end of which is an irregular cylindrical structure with a concave platform. The depth of the concave platform is determined according to the thickness of the wire, and the wire outlet is placed on the concave platform for easy welding; the upper end of the copper nut is an M10 threaded rod. Due to the board size constraints of the coil terminal board, this structure can save space for the outlet terminal and facilitate wire connection during assembly.

[0108] Fig.17 Provides a schematic diagram of the high-voltage winding outlet position. Fig.18 For the corresponding Fig.17 The upper end of the high-voltage winding leads directly to the high-voltage side clamp support insulator for easy wiring; the lower end of the high-voltage winding has ±5% tapping, which are X1, X2, X3 (Y1, Y2, Y3, Z1, Z2, Z3) Fig.18 The low-voltage connecting lead can be moved at the same time to easily adjust the gear position. Figure 6 After the No. 2 high voltage winding side coil and No. 3 low voltage winding side coil marked in the middle are made, follow the Figure 6The relative positions are assembled, and the lead wires are made after assembly. A, X1, X2, X3 (B, Y1, Y2, Y3; C, Z1, Z2, Z3) of the high-voltage grid side winding are all externally connected to the support plate. This connection method is very convenient for realizing the high-voltage voltage gear ±5% conversion method. The triangle connection of the main coil on the low-voltage side is completed by connecting the abc phase terminal rows, and then the 311-381 phases of each phase winding of abc are connected to the external terminal row. For specific connection methods, refer to Fig.19 , taking one of the groups as an example, Fig.19 The figure shows the location of the lead wires on the low voltage winding side leading to the terminal block. For the convenience of connection, the abc and ±5% tapping terminals of the fourth group are also led to the external terminal block. Fig. 20 As shown, Fig. 20 The schematic diagram of the outgoing line position of the fourth group on the low-voltage winding side is shown. So far, the relevant description of the technical key points of the high and low voltage windings in this example has been completed. It should be noted that the selection of the number of turns and wire gauge of the wire must also comprehensively consider other technical parameters such as the impedance and temperature rise of the product.

[0109] In summary, traditional phase-shifting transformers mainly use nomex paper as conductor insulation and the coil is a non-encapsulated insulation form with overall varnish immersion. This insulation method has weak adaptability to the environment. For some environments with poor operating conditions, the product is prone to insulation degradation caused by moisture. In addition, since the high and low voltage windings of this type of product have no rigid support, the overall short-circuit resistance is relatively weak.

[0110] However, since the multi-pulse phase-shifting transformer has more low-voltage terminals, if the epoxy casting structure is used, there are great difficulties in wire winding and low-voltage terminal outlet arrangement. The epoxy casting multi-pulse phase-shifting transformer described in this example will find a solution to the above difficulties. This example takes a single 48-pulse phase-shifting transformer as an example, and its turns selection, wire arrangement, and terminal arrangement are described in detail above.

[0111] In addition, the electrical isolation requirements between the low-voltage winding and the high-voltage winding must also be considered. The withstand voltage design ensures that the transformer can withstand electrical stress and avoid breakdown and damage in a high-voltage working environment. The relative voltage between the first winding and the last winding in the three groups on the low-voltage winding side is 10kV, and the primary and secondary insulation of the transformer is considered to be 10kV. Figure 4As shown, the three large groups (group 1, group 2 and group 3) on the secondary side are electrically connected in series, so that the voltage and current of each winding can be gradually transmitted, and finally the output voltage of the entire low-voltage side is realized. The first winding refers to the first turn position in the phase-shift winding or the main winding, depending on the winding order. The last winding is the last winding in the last large group (group 3) in the secondary winding (low-voltage winding). The number of turns corresponding to this winding is the end of the low-voltage winding. Because the secondary windings are connected in series, the voltage difference between the first winding and the last winding is 10kV, which is about √3 times the sum of the voltages of the secondary windings. It is necessary to ensure electrical isolation and withstand voltage safety between the windings to ensure that no breakdown or electrical short circuit occurs between the windings during normal operation or failure (such as short circuit, overvoltage, etc.). In addition, in order to ensure that the electrical isolation between two adjacent windings is safe enough in a high voltage environment and will not cause breakdown or insulation failure due to excessive voltage, each large group in the low-voltage winding (such as group 1, group 2, group 3) has a certain voltage difference between each group, and the withstand voltage between two adjacent windings is required to reach 16kV. Group 3 and group 4 are the electrical connection parts of the two groups on the low-voltage side. The voltage difference between them also needs to withstand high electrical stress, so they need to be designed to withstand a voltage of 16kV.

[0112] In addition, in order to ensure that the transformer will not break down under short-term overvoltage or instantaneous electrical shock, each large group (such as group 1, group 2, group 3) contains multiple small groups responsible for different voltage regulation and transmission. The electrical insulation performance between these groups must also be guaranteed to prevent voltage breakdown. The insulation design between each group is required to withstand a voltage of 5.4kV and last for 1 minute. For example, when a short circuit occurs, the voltage may rise instantly, and the withstand voltage design ensures that the insulation between the groups can withstand the voltage shock in a short time.

[0113] Example 3

[0114] This application also provides Figure 3 , Figure 4 and Figure 5 . Figure 3 This is the working principle diagram of multi-pulse phase-shifting transformer, frequency converter and frequency conversion motor. Figure 4 It is a schematic diagram of the inverter output terminals of each group connected in series to form a three-phase power supply (with a phase difference of 120°). Figure 5It is a schematic diagram of the connection between the outlet terminal and the outlet panel after the multi-pulse transformer is cast. The valve side winding (i.e., low-voltage winding) and the grid side winding (i.e., high-voltage winding) of the transformer jointly complete the power conversion and regulation functions of the frequency conversion system. Since the high-voltage winding and the low-voltage winding have different functional names in different applications, there will be annotations. In this application, the valve side winding (i.e., low-voltage winding) and the grid side winding (i.e., high-voltage winding) of the transformer jointly complete the power conversion and regulation functions of the frequency conversion system.

[0115] Figures 3 to 5 In the diagram, each phase of the transformer is marked as U, V, and W, and these three phases provide three-phase AC power to the load. U1 to U8, V1 to V8, and W1 to W8 represent each phase-shifted winding unit in the U phase, V phase, and W phase, respectively. These numbers indicate the specific position of each phase winding at different phase shift angles. The numbers after each number (such as U1, U2, ...U8) indicate the specific order and position of the phase winding. The phase difference between each set of windings is usually distributed according to a certain angle, such as 7.5° or other standard values. It should be noted that for the transformer, the input end is marked as ABC and the low-voltage side output end is marked as abc according to the marking habits of technicians in this field. For the power unit of the inverter, the marking habit of technicians in this field is to name the port of the input end as RST, that is, the lead wire terminal is called a1b1c1...a8b8c8 on the secondary side of the transformer, but when entering the entrance of the inverter power unit, the name of the wire is changed to RST. Figure 3 In the figure, M represents the variable frequency motor. The entire variable frequency system is a power supply device that provides the variable frequency motor with adjustable frequency and adjustable voltage. Figure 5 In the installation process, the factory wiring area refers to the internal connection area between the transformer and the external terminal block, where the internal electrical connection and testing of the equipment are carried out. The user wiring area refers to the wiring area when the user actually uses and installs the transformer after the transformer leaves the factory. The user wiring area usually includes the part that connects the transformer to external loads, power grids and other equipment. During the installation process, the output winding (low-voltage winding) of the transformer will be connected to the user's equipment (such as motors, loads, control systems, etc.) through the wiring area.

[0116] Grid-side winding (high-voltage winding), the grid-side winding is located on the high-voltage side (primary side), responsible for receiving grid power and building the electromagnetic field of the transformer; valve-side winding (low-voltage winding), as before, the valve-side winding is located on the low-voltage side (secondary side) of the transformer, and its main function is to convert the 10kV input voltage into an acceptable working voltage for IGBT, and convert the AC power into power suitable for three-phase motor drive through the AC-DC-AC conversion of the IGBT power unit. In the low-voltage winding of each phase, it is further divided into 4 groups, of which the three major groups (each containing 8 small groups) complete the AC-DC-AC conversion through the IGBT power unit, converting the electric energy into a voltage and frequency suitable for the motor. The fourth group of windings is used to provide power for the fan and thermostat of the transformer to ensure the stable operation of the transformer body. Among them, the low-voltage winding is designed as an epoxy casting structure to ensure the mechanical strength and insulation performance of the structure. Each phase of the low-voltage winding is divided into four groups, the first three groups are used for the phase shift function, and the phase adjustment and power transmission of the current are ensured through the cooperation of the phase shift winding and the main winding. The power unit of the inverter is connected to the low-voltage winding, and the adjustable frequency and voltage provided by the inverter are used to adjust the speed and output power of the motor. The low-voltage winding plays a vital role in the frequency conversion system. Each phase of the low-voltage winding is divided into 4 groups, of which the first three groups are responsible for phase shifting and power transmission, and the fourth group provides an independent auxiliary power supply.

[0117] In the collaboration between the phase-shift winding and the main winding, each low-voltage winding contains 8 phase-shift windings and 8 main windings. The phase-shift winding is responsible for adjusting the phase angle, and the phase-shift winding and the main winding are responsible for power transmission. The phase-shift winding adjusts the phase of the voltage and accurately controls the phase-shift angle of the output voltage to ensure the stable operation of the entire system. Among them, the tail end of the phase-shift winding and the main winding are directly connected to the head end to form a continuous current path, thereby ensuring the effective transmission of power.

[0118] The frequency conversion system (multi-pulse transformer + inverter) forms a complete power conversion system by connecting with the three-phase motor. The inverter can adjust the output voltage and frequency to control the speed and power output of the three-phase motor. The inverter can adjust the output frequency according to the load demand, thereby adjusting the speed of the motor, and is widely used in variable speed drives, air conditioners, pumps, fans and other equipment. In addition, through the coordinated work between the multi-pulse transformer and the inverter, the AC power can be converted into AC power with adjustable voltage and frequency suitable for the operating conditions of the motor, meeting the power demand of the motor under different working conditions. The frequency conversion system not only provides the power required for the motor drive, but also optimizes the operating performance of the motor through phase shift regulation and frequency regulation, improves the energy efficiency of the system, and reduces the interference and pollution of harmonics on the grid voltage.

[0119] In summary, in each of the above embodiments, an epoxy cast multi-pulse phase-shifting transformer is provided, which is particularly suitable for the frequency conversion field. The epoxy cast multi-pulse phase-shifting transformer is superior to the traditional transformer design in many aspects, especially in voltage regulation accuracy, mechanical strength and system stability, as shown below.

[0120] Improved voltage regulation accuracy: The transformer is designed with a ±5% voltage regulation function. By switching the tap terminals, it can cope with different grid voltage fluctuations and ensure a stable output voltage, thereby improving the reliability and adaptability of the system; Accurate phase shift angle adjustment: By accurately adjusting the number of turns of the phase shift winding, the phase angle of the voltage can be effectively adjusted to ensure that the phase shift angle error of the output voltage is less than 0.5°. This design reduces the interference and pollution of the frequency conversion system to the grid voltage, and high-order harmonics can be offset by the characteristics of the transformer itself; High reliability and durability: The epoxy casting design significantly improves the insulation performance and short-circuit resistance of the transformer. This design can effectively prevent the aging of traditional winding insulation materials due to moisture or harsh environment, ensuring the long-term stable operation of the transformer under high load conditions; Compact and efficient design: Through the staggered terminal row design and optimized winding layout, the overall structure of the transformer is more compact and the electrical connection is more stable. This not only improves the space utilization of the terminal row, but also reduces the mutual interference of the wire arrangement, and improves the operational reliability of the system; Enhanced short-circuit performance: The design of epoxy casting and rigid support enables the transformer to withstand higher electrical stress, enhances the anti-interference ability to short-circuit conditions, and improves the safety and reliability of the transformer when a fault occurs; 48-pulse rectification optimization: In the design of the low-voltage winding, the combination of the phase-shifting winding and the main winding enables the transformer to achieve a 48-pulse rectification function, reduces the harmonic content of the current, and improves the conversion quality of electric energy. This design is widely used in high-power systems that require a stable DC power supply and high-power systems that require AC-DC-AC conversion; Wide applicability: The transformer is highly flexible and configurable, and can be adjusted according to different working conditions (such as grid voltage fluctuations, load requirements, etc.), and is suitable for multiple fields such as industry, renewable energy, and efficient power transmission; Reduced maintenance costs: Since the design of the outlet terminals of the high-voltage winding and the low-voltage winding is easy to connect and replace, maintenance work becomes easier, greatly reducing the maintenance cost and downtime of the transformer. In summary, by adopting epoxy casting structure and precise phase shifting regulation technology, the multi-pulse phase shifting transformer of the present application has efficient voltage regulation and low harmonic characteristics, which can significantly improve the stability, efficiency and safety of the transformer, and is widely used in industrial equipment, variable frequency drives and high-power power systems that require precise power regulation.

[0121] The above description is only an optional embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. An epoxy cast multi-pulse phase-shifting transformer, characterized in that: The frequency conversion system suitable for AC / DC conversion, the epoxy cast multi-pulse phase-shifting transformer comprises: An iron core, located at the center of the transformer body, for supporting the high voltage winding and the low voltage winding and providing a magnetic flux magnetic circuit; The high voltage winding is located in the inner layer of the core and is used for input voltage conversion tasks; The low voltage winding is located outside the high voltage winding and is used to adjust the phase shift angle according to the phase shift principle; Lead terminals and terminal blocks, the lead terminals are fixedly connected to the terminal blocks by welding or nuts, the lead terminals are used to connect the high-voltage winding, the low-voltage winding and the lead terminals, and the lead terminals are also led out to an external circuit through the terminal blocks; Copper nuts, each winding is connected to the terminal block through the copper nuts.

2. The epoxy cast multi-pulse phase-shifting transformer according to claim 1 is characterized in that: The iron core adopts a five-level stacked iron design; The distance between the iron core and the high-voltage winding meets the requirements of power frequency withstand voltage and lightning impulse voltage.

3. The epoxy cast multi-pulse phase-shifting transformer according to claim 1, characterized in that: The high voltage winding adopts single spiral winding and segmented cylinder structure design; The number of turns of the high-voltage winding is designed to be ±5% tapped, and the number of turns ranges from 476 to 431 turns, wherein the tapping terminal is located at the upper end or the lower end of the high-voltage winding, and multi-gear switching is achieved through the tapping terminal; The high voltage winding supports ±5% voltage regulation function.

4. The epoxy cast multi-pulse phase-shifting transformer according to claim 1, characterized in that: The low voltage winding is designed by epoxy casting; Each phase winding of the low voltage winding is divided into 4 groups; The first three groups of each phase winding are main power supply groups for phase shifting function, wherein each group of each phase winding includes 8 phase shifting windings and 8 main windings, the tail end of the phase shifting winding is directly connected to the head end of the corresponding main winding to form a continuous current path, the phase shifting winding is used to adjust the angle, and the main winding and the phase shifting winding are used together for power transmission; The fourth group of windings of each phase is an auxiliary winding for supplying power to the fan and the thermostat.

5. The epoxy cast multi-pulse phase-shifting transformer according to claim 1, characterized in that: The terminal rows are arranged in a staggered manner.

6. A design method for epoxy cast multi-pulse phase-shifting transformer, characterized in that: The method is used for the epoxy cast multi-pulse phase-shifting transformer according to any one of claims 1 to 5, and the method comprises: For core design, The core is designed according to a five-level stacking and laminating type, and the five-level stacking and laminating type design meets the flux requirements of the transformer; The distance between the iron core and the high-voltage winding is determined according to the power frequency withstand voltage and lightning impulse voltage requirements.

7. The method according to claim 6, characterized in that The method further comprises: For high voltage winding design, Calculating the rated number of turns of the high voltage winding according to the input voltage; Divide the subsequent turns according to the ±5% tapping position and mark them as +5%, rated, and -5% respectively; The main body of the high-voltage winding is designed using a single spiral winding and a segmented cylinder structure; The tap terminal is arranged at the upper end or the lower end of the high-voltage winding and is connected to the terminal block through the copper nut to realize the tap adjustment function.

8. The method according to claim 6, characterized in that The method further comprises: For low voltage winding design, Dividing the low voltage winding into four groups; The first three groups are designed as the main power supply groups, each group contains 8 phase-shifting windings and 8 main windings, and the phase-shifting windings and the main windings are connected end to end to form a continuous current path; Designing the fourth group as the auxiliary winding; Arranging the phase-shifting windings in sequence according to the phase-shifting angles; The main winding and the phase-shifting winding are connected and arranged in sequence according to the phase-shifting angle.

9. The method according to claim 6, characterized in that The method further comprises: For lead and terminal block design, The lead terminals of the high voltage winding and the low voltage winding are fixedly connected to the terminal block by welding or nuts; Connecting the tail end of the phase-shifting winding and the head end of the main winding via a common lead terminal; The terminal rows are arranged in a staggered manner.

10. The method according to claim 6, characterized in that The method further comprises: The coils of the low-voltage winding and the high-voltage winding are cast and fixed.

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