CN113724964A

CN113724964A - Transformer and insulation packaging method thereof

Info

Publication number: CN113724964A
Application number: CN202110826523.1A
Authority: CN
Inventors: 张浩军; 王子京; 胡小情; 景遐明; 张泽龙; 黄朱勇
Original assignee: Huawei Digital Power Technologies Co Ltd
Current assignee: Huawei Digital Power Technologies Co Ltd
Priority date: 2021-07-21
Filing date: 2021-07-21
Publication date: 2021-11-30
Anticipated expiration: 2041-07-21
Also published as: CN113724964B

Abstract

The application provides a transformer and an insulation method of the transformer, and relates to the technical field of electronics. The transformer comprises a primary winding, a secondary winding, an iron core and a packaging shell. Wherein the iron core passes through the primary winding and the secondary winding. The primary winding is cast from epoxy to form a first cast body. And the secondary winding, the first casting body and the iron core are cast into a whole by organic silica gel to form a second casting body. And the packaging shell is used for packaging the second casting body, wherein the inner surface of the packaging shell is coated with the semi-conductive shielding layer. The transformer can ensure the electrical performance of the transformer and improve the thermal conductivity of the insulating material in the transformer. Thereby improving the service life and the working performance of the transformer.

Description

Transformer and insulation packaging method thereof

Technical Field

The embodiment of the application relates to the technical field of electronics, in particular to a transformer and an insulation packaging method of the transformer.

Background

A solid-state transformer (SST), also called a Power Electronic Transformer (PET), is a high-frequency coupling device based on the electromagnetic induction principle. The solid-state transformer combines the power electronic technology with the high-frequency transformer, integrates the functions of electrical isolation, voltage conversion, reactive compensation, power transmission and control, energy bidirectional flow and the like, and greatly improves the intelligent level of power grid equipment by integrating the traditional transformer and power electronic equipment. Compared with the traditional transformer, the SST has the advantages of small volume, light weight, environmental friendliness, configurable intelligent control unit and the like, is convenient for the equipment level to cooperate to realize the self-healing function, can also perform networking communication, and realizes the intellectualization of a power grid.

However, the hysteresis loss of the iron core in the SST, the winding loss of the coil, the dielectric loss of the insulating material and the heating of the insulating material at high frequency can cause local over-high temperature, and meanwhile, when the SST operates in a high-voltage environment, the internal insulation often generates a local discharge phenomenon, which can cause the aging and damage of the insulating material, finally cause thermal breakdown, and seriously affect the service life of the equipment and the working efficiency of the transformer. Therefore, how to improve the heat dissipation performance of the insulating material in the SST and reduce the partial discharge risk of the SST is a problem which needs to be solved urgently.

Disclosure of Invention

The embodiment of the application provides a transformer and an insulation packaging method of the transformer, and aims to improve the heat conductivity of an insulation material in the transformer while ensuring the electrical performance of the transformer so as to improve the service life and the working performance of the transformer.

A first aspect of embodiments of the present application provides a transformer that includes a primary winding, an additional winding, an iron core, and an enclosure. The iron core needs to penetrate through the primary winding and the secondary winding to form a magnetic circuit, and energy is transferred from the primary winding to the secondary winding. And the primary winding is poured by epoxy resin to form a first pouring body, so that the purpose of isolating the primary winding from the iron core is achieved. And then, pouring the secondary winding, the first pouring body, the iron core and the packaging shell by using organic silica gel to form a second pouring body. Wherein, the encapsulation shell is used for encapsulating the second casting body, and the inner surface of the encapsulation shell is coated with a semi-conductive shielding layer.

In the transformer structure, the insulating medium between the primary winding and the iron core is epoxy resin, and the area between the primary winding and the iron core is the main insulating area, so that the requirement of the transformer on the insulating property can be met by adopting the epoxy resin with good insulating property. And other areas adopt softer organic silica gel for insulation, so that the pouring stress can be greatly reduced, and the phenomenon that the iron core cracks is avoided. Meanwhile, the organic silica gel has high thermal conductivity, so that the thermal conductivity of the insulating material in the transformer can be effectively improved, and the service life and the working performance of the transformer are improved.

In an alternative embodiment, the outer surface of the first casting is coated with a semiconducting shield layer. The semi-conductive shielding layer is coated on the outer surface of the first casting body, so that electrical isolation can be effectively carried out, the occurrence of partial discharge can be reduced, and the electrical performance of the transformer can be ensured.

In an alternative embodiment, the primary winding of the transformer is made of copper wire and a semiconducting layer, which may be semiconducting paper, semiconducting tape, or the like, wound around the outside of the copper wire. The copper wire is protected, meanwhile, electrical isolation is further carried out, and the occurrence of the electric leakage phenomenon is reduced.

In an alternative embodiment, the semi-conductive layer and the copper line may be equipotential treated. Therefore, the phenomenon that the electric field is distorted due to nonuniform field intensity distribution can be avoided. When the field intensity is uniformly distributed, the partial discharge phenomenon is reduced, so that the partial discharge risk of the transformer can be further reduced, and the electrical performance of the transformer is improved.

In an alternative embodiment, the thickness of the semiconducting layer is between 0.05 mm and 0.2 mm. I.e. the minimum thickness of the semiconducting layer is 0.05 mm to ensure the shielding effect of the semiconducting layer. The maximum thickness is 0.2 mm, so that the problem of large gap caused by over-thickness of the semi-conductive layer is avoided.

In an alternative embodiment, the epoxy is cast to a thickness of between 4 mm and 12 mm of the primary winding. Namely, the minimum casting thickness is 4 mm, so as to ensure the insulation effect between the primary winding and the iron core. The maximum casting thickness is 12 mm, so that bubbles generated during casting can be reduced, and the casting stress is reduced. Thereby improving the insulating property of the transformer and reducing the occurrence of partial discharge.

In an alternative embodiment, the thickness of the semiconductive shield is between 0.2 mm and 0.5 mm. Similarly, the minimum thickness of the semiconductive shielding layer is 0.2 mm, so as to ensure the shielding effect of the semiconductive shielding layer. The maximum thickness is 0.5mm, so that the problem of large gap caused by over-thickness of the semiconductive shielding layer is avoided.

In an alternative embodiment, the epoxy resin and the silicone rubber have high thermal conductivity, wherein the epoxy resin can be doped organically to improve the thermal conductivity, and the silicone rubber itself has high thermal conductivity. The use of the two materials can greatly improve the heat conductivity of the insulating medium in the transformer, reduce the aging and damage speed of the insulating material, and finally improve the service life of equipment and the working efficiency of the transformer.

A second aspect of an embodiment of the present application provides an insulation packaging method for a transformer, including:

and winding the copper wire by using semi-conductive paper to obtain a primary winding. And fixing the primary winding in a mold, and pouring the primary winding by using epoxy resin to obtain a first pouring body. And forming a semiconductive shielding layer on the outer surface of the first casting body. The iron core, the secondary winding, and the first casting are assembled such that the iron core passes through the secondary winding and the first casting. And (4) pouring the assembled iron core, the secondary winding and the first pouring body into a whole by using organic silica gel to obtain a second pouring body. The packaging shell is used for packaging the second pouring body, and the inner surface of the packaging shell is coated with a semi-conductive shielding layer.

According to the transformer structure obtained by the insulation packaging method, the insulation medium between the primary winding and the iron core is epoxy resin, and the area between the primary winding and the iron core is a main insulation area, so that the requirement of the transformer on the insulation performance can be met by adopting the epoxy resin with good insulation performance. And other areas adopt softer organic silica gel for insulation, so that the pouring stress can be greatly reduced, and the phenomenon that the iron core cracks is avoided. Meanwhile, the organic silica gel has high thermal conductivity, so that the thermal conductivity of the insulating material in the transformer can be effectively improved, and the service life and the working performance of the transformer are improved.

In an alternative embodiment, the semi-conductive paper and the copper wire may be treated equipotentially. Therefore, the phenomenon that the electric field is distorted due to nonuniform field intensity distribution can be avoided. When the field intensity is uniformly distributed, the partial discharge phenomenon is reduced, so that the partial discharge risk of the transformer can be further reduced, and the electrical performance of the transformer is improved.

A third aspect of embodiments of the present application provides an active circuit, including at least one transformer as described in the first aspect or any one of the implementations of the first aspect.

The active circuit may be a circuit for realizing functions of frequency conversion, voltage transformation, phase transformation, rectification, inversion, switching and the like for regulating voltage/current. The power supply may be an inverter circuit, a rectifier circuit, a transformer circuit, or the like.

Drawings

Fig. 1 is a basic schematic diagram of a solid-state transformer according to an embodiment of the present disclosure;

fig. 2 is a schematic structural diagram of a solid-state transformer according to an embodiment of the present disclosure;

fig. 3 is a schematic structural diagram of another transformer according to an embodiment of the present disclosure;

fig. 4 is a schematic structural diagram of a first casting body provided in an embodiment of the present application;

fig. 5 is a schematic structural diagram of a primary winding according to an embodiment of the present disclosure;

fig. 6 is a schematic flowchart of an insulation packaging method for a transformer according to an embodiment of the present disclosure.

Detailed Description

The terms "first," "second," "third," "fourth," and the like in the description and in the claims of the present application and in the drawings described above, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "corresponding" and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

In the embodiments of the present application, words such as "exemplary" or "for example" are used to mean serving as an example, instance, or illustration. Any embodiment or design described herein as "exemplary" or "e.g.," is not necessarily to be construed as preferred or advantageous over other embodiments or designs. Rather, use of the word "exemplary" or "such as" is intended to present concepts related in a concrete fashion.

For clarity and conciseness of the following descriptions of the various embodiments, a brief introduction to the related art is first given:

the transformer is a device for changing alternating voltage by using the principle of electromagnetic induction, and has the functions of voltage transformation, current transformation, impedance transformation, isolation, voltage stabilization and the like. The main components of the device are a primary coil, an iron core and a secondary coil, wherein the primary coil is connected with a power supply, and the secondary coil is connected with a load. When the primary coil of the transformer is connected with an alternating current power supply, alternating magnetic flux is generated in the iron core, so that an alternating magnetic field is generated, and then the secondary coil can generate induced electromotive force to finish energy transfer.

According to the classification of the insulating medium, the transformer may be classified into a solid-state transformer, a liquid (oil) -immersed transformer, a gas-filled transformer, and the like. Among them, the solid-state transformer is also called as a power electronic transformer, and is a high-frequency coupling device based on the electromagnetic induction principle. The solid-state transformer combines a power electronic technology and a high-frequency transformer, realizes the conversion of electric energy with one power characteristic into electric energy with another power characteristic, integrates the functions of electrical isolation, voltage conversion, reactive compensation, power transmission and control, energy bidirectional flow and the like, and greatly improves the intelligent level of power grid equipment by integrating the traditional transformer and the power electronic equipment. Compared with the traditional transformer, the SST has the outstanding characteristics of realizing flexible control of primary side current, secondary side voltage and power thereof, improving the quality of electric energy after being applied to a power system, improving the stability of the system and realizing flexible power transmission modes and real-time control of power flow in a power market.

Fig. 1 is a basic schematic diagram of a solid-state transformer according to an embodiment of the present disclosure, and as shown in fig. 1, the solid-state transformer includes a power electronic conversion module, a high-frequency transformation module, and a control module. Firstly, the power electronic conversion module converts an input power frequency alternating current signal into a higher frequency signal under the control of the control module, then inputs the higher frequency signal into the high frequency transformation module, the high frequency transformation module couples the higher frequency signal to the secondary side according to the electromagnetic induction principle, and then the power electronic conversion module restores the higher frequency signal into the power frequency alternating current for output. The implementation methods of the frequency conversion part are divided into two categories: one is that there is no direct current link in the conversion process, and direct alternating current is converted into alternating current. The other is that an intermediate direct current link exists in the change process, namely alternating current is firstly converted into direct current and then converted into alternating current.

Fig. 2 is a schematic structural diagram of a solid-state transformer according to an embodiment of the present disclosure, and as shown in fig. 2, the solid-state transformer includes an enclosure 201, an outlet terminal 202, an iron core 203, a primary winding 204, and a secondary winding 205. The iron core 203 may be formed by a manganese-zinc ferrite core or an iron-based amorphous core, the primary winding 204 and the secondary winding 205 may be formed by a winding frame and three layers of insulating wires, and the outgoing terminal 202 is a cable-type outgoing line, wherein the inside of the package case 201 is encapsulated by an insulating medium for insulating conductors of different potentials, and simultaneously, the insulating medium may also serve as a mechanical fixation function, and the insulating medium is generally made of epoxy resin (epoxy resin).

When the transformer works, the hysteresis loss of the special core, the winding loss of the coil and the dielectric loss of the insulating medium under high frequency generate heating phenomena, and the heating phenomena cause overhigh local temperature, thereby influencing the service life of the transformer and the working efficiency of the transformer. Therefore, the heat conduction performance of the insulating medium becomes a key, and the longer the service life, the higher the working efficiency and the better the performance of the transformer with the better heat dissipation performance of the insulating medium are.

Epoxy resin is also called artificial resin, is an organic high molecular polymer containing more than two epoxy groups in a molecular structure, and is thermoplastic plastic. The epoxy resin can be subjected to a crosslinking reaction with various curing agents to form an insoluble and infusible high polymer with a three-dimensional network structure, so that the epoxy resin has excellent insulating property, mechanical property, chemical stability and the like, and is a good material used as an insulating medium of a transformer. However, epoxy resins have low intrinsic thermal conductivity (0.15W/(m.K) -0.20W/(m.K)), resulting in poor heat dissipation properties. Therefore, in order to solve the above-mentioned problem of local heat generation, it is necessary to improve the heat conductivity of the epoxy resin, thereby improving the performance of the entire transformer.

At present, two methods are used for improving the thermal conductivity of epoxy resin, one is to improve the thermal conductivity of epoxy resin by constructing a semi-crystalline epoxy resin structure, and the intrinsic thermal conductivity of biphenyl semi-crystalline epoxy resin is improved to 0.96W/(m.K) at most by constructing biphenyl semi-crystalline epoxy resin, but the epoxy resin obtained by the method has high cost and high viscosity, and the improved thermal conductivity is limited (the maximum thermal conductivity is not more than 1W/(m.K)), so that the epoxy resin is not suitable for transformer molding. Therefore, the intrinsic thermal conductivity of the epoxy resin is mainly improved by the second method, and the composite material of the modified epoxy resin is formed by adding high thermal conductivity fillers such as boron nitride, silicon nitride, aluminum oxide, silicon oxide and the like, so that the thermal conductivity of the composite material is far higher than that of the original epoxy resin, and the performance of the whole transformer is improved.

However, the existing transformer is mainly formed by using an integral casting molding method, as shown in fig. 2, firstly, each component of the transformer is overlapped, and then, the epoxy resin is used for integral potting, in this case, if the epoxy resin doped with the high thermal conductive filler is used as the insulating material, the viscosity of the modified epoxy resin will be rapidly increased due to the doping of the filler, which will cause that air bubbles are easily introduced in the preparation process, greatly increase the possibility of the partial discharge phenomenon in the transformer, and bring harm to the dielectric property of the transformer. It can be understood that if the modified epoxy resin achieves sufficient thermal conductivity, the doping amount of the high thermal conductivity filler can generally reach more than half of the whole material, the insulation performance of the modified epoxy resin can be continuously reduced along with the increase of the doping amount of the high thermal conductivity filler, and the partial discharge phenomenon is easier to occur. Meanwhile, epoxy resin is used for integral casting, and shrinkage stress of the epoxy resin in the curing process is overlarge, so that the iron core is cracked, the magnetic induction is reduced, and the performance of the transformer is deteriorated.

The partial discharge phenomenon will be briefly described below. The partial discharge is a discharge that occurs only partially in an insulator in a high-voltage electrical apparatus, and does not occur through a gap between conductors to which a voltage is applied, and may occur in the vicinity of the conductors or elsewhere. Partial discharge is an important cause of the ultimate occurrence of insulation breakdown in high-voltage electrical equipment, and is also an important indicator of insulation degradation.

The insulator of the power equipment can generate partial discharge under the action of a strong enough electric field, and the discharge is limited to only cause partial short circuit without forming a conductive channel. Each partial discharge has some influence on the insulating medium, a slight partial discharge has little influence on the electric equipment, which results in slow insulation strength of the insulating medium of the electric equipment, and a strong partial discharge can quickly reduce the insulation strength. However, whether slight partial discharge or strong partial discharge exists, each time of discharge, the insulating medium receives impact of high-energy electrons or accelerated electrons, and long-term partial discharge can cause various physical effects and chemical effects, destroy the molecular structure of the insulating medium, cause insulation deterioration and finally influence the service life of electric power equipment.

In the transformer, the local discharge is caused by the existence of air bubbles in the insulating medium, and the air and the insulating material have different dielectric coefficients, so that the field intensity is easily distorted, and the local discharge phenomenon occurs when the local field intensity reaches the breakdown field intensity. As can be seen from the above, in order to improve the thermal conductivity of the insulating medium in the transformer, a high thermal conductive filler needs to be added to the insulating material epoxy resin, and the addition of the high thermal conductive filler inevitably increases the number of bubbles, so that partial discharge of the transformer is increased in the case of integral casting molding, and the electrical performance of the transformer is seriously affected. Therefore, how to ensure the electrical performance of the transformer while improving the thermal conductivity of the transformer is a problem that needs to be solved.

The embodiment of the application provides a transformer and an insulation packaging method of the transformer, and when modified epoxy resin with higher heat conductivity is used as a transformer insulation medium, a series of semi-conductive shielding layers are added to reduce the generation of a partial discharge phenomenon, so that the electric performance of the transformer is ensured, and the heat conductivity of an insulation material in the transformer is improved, so that the service life and the working performance of the transformer are improved.

Fig. 3 is a schematic structural diagram of another transformer provided in the embodiment of the present application, and as shown in fig. 3, the transformer includes: the packaging shell 201, the iron core 203, the primary winding 204 and the secondary winding 205.

The transformer is manufactured by adopting a secondary casting molding method. First, the primary winding 204 is cast with a modified epoxy resin to obtain a first cast body. Thus, the insulating medium between the primary winding 204 and the core 203 is epoxy, and an isolation shield between the primary winding 204 and the core 203 is required, as will be described in detail below.

And then combining the first casting body, the secondary winding 205 and the iron core 203, wherein the iron core 203 needs to penetrate through the primary winding 204 and the secondary winding 205, and after combination, the combined body is cast by using organic silica gel to obtain a second casting body. The secondary winding 205 is also shielded from the core 203.

Finally, the second potting body is encapsulated by an encapsulation shell 201, and a final transformer is obtained, wherein the inner surface of the encapsulation shell 201 is coated with a semi-conductive shielding layer.

Firstly, in an integrated casting scene, since the shrinkage stress of the epoxy resin in the curing process is too large, which may cause the iron core to crack, the transformer provided in the embodiment of the present application adopts a secondary casting method, and the primary winding 204 is cast first to obtain the first casting body. Because the primary winding 204 and the iron core 203 are in the main insulation area of the transformer, the epoxy resin with better insulation performance is adopted to cast the primary winding 204, so that the insulation medium between the primary winding 204 and the iron core 203 is changed into the epoxy resin with better insulation performance, the insulation medium between the primary winding 204 and the iron core 203 is ensured to be more reliable, and the performance of the transformer is ensured.

It can be understood that the epoxy resin in the embodiment of the present application is a modified epoxy resin, and has high thermal conductivity, so that the heat dissipation capability of the insulating medium can be improved, the phenomenon of local over-high temperature caused by hysteresis loss of the special core, winding loss of the coil and dielectric loss of the insulating medium under high frequency is reduced, and the service life of the transformer is prolonged. The thermal conductivity of the epoxy resin can be changed by adding high thermal conductive filler, such as boron nitride, silicon nitride, aluminum oxide, silicon oxide, and the like, preferably, the thermal conductivity of the modified epoxy resin can be kept between 1.0W/(m.K) -2.0W/(m.K), the dielectric strength needs to be more than 25kV/mm, the dielectric loss is less than 0.5 percent, and the glass transition temperature Tg is more than or equal to 120 ℃.

After forming first pouring body, combine first pouring body, iron core 203 and secondary winding 205 for iron core 203 passes secondary winding 205 and first pouring body, produce too big shrinkage stress in order to prevent epoxy when the solidification, lead to the iron core fracture, can adopt softer, the higher organic silica gel of thermal conductivity pours the assembly, obtain the second pouring body, can reduce shrinkage stress like this, avoid the iron core fracture, can improve insulating medium's heat conductivility simultaneously, improve the life-span of transformer.

The term "silicone gel" as used herein means a compound having an Si-C bond and at least one organic group directly bonded to a silicon atom, and conventionally, a compound having an organic group bonded to a silicon atom via oxygen, sulfur, nitrogen or the like is also used as an organosilicon compound. The organic silica gel has the basic properties of low surface tension, small viscosity-temperature coefficient, high compressibility, high gas permeability and the like, and has excellent characteristics of high and low temperature resistance, electrical insulation, high oxidation resistance stability and the like, so the organic silica gel can also be used as an insulating material of a transformer, but the insulating property of the organic silica gel is lower than that of epoxy resin, in order to ensure the working performance of the transformer, epoxy resin is still required to be used as the insulating material between the primary winding 204 and the iron core 203, namely a main insulating area in the transformer, and the organic silica gel can be used as the insulating material in other areas to reduce shrinkage stress and protect the iron core.

Finally, the second potting body is encapsulated by an encapsulation shell 201, and a final transformer is obtained, wherein the inner surface of the encapsulation shell 201 is coated with a semi-conductive shielding layer for electrostatic isolation and partial discharge possibility reduction. The semiconductive shielding layer can be composed of silicon carbide SiC or graphite modified epoxy resin, in a preferred scheme, the glass transition temperature Tg of the graphite modified epoxy resin is greater than or equal to 120 ℃, the surface resistivity of the formed semiconductive shielding layer is 100 ohm to 2000 ohm, and the semiconductive shielding layer can be processed in a spraying or brushing mode and ranges from 0.2 mm to 0.5 mm.

In order to reduce the partial discharge phenomenon, the conductor can be effectively isolated and shielded, so that even if bubbles are generated in the insulating medium, a distortion electric field cannot be generated, the possibility of the partial discharge phenomenon is greatly reduced, the electrical performance of the transformer is improved, and the service life of the transformer is prolonged. Therefore, the primary winding and the secondary winding can be obtained by effectively isolating the conductors (coils) in the primary winding or the secondary winding.

Fig. 4 is a schematic structural diagram of a first casting body according to an embodiment of the present application, and as shown in fig. 4, the first casting body includes: primary winding 204, semiconductive shield 401, and outlet terminal 202.

The primary winding 204 is sealed by the high-thermal-conductivity epoxy resin, and similarly, the high-thermal-conductivity epoxy resin improves the heat dissipation capacity of the insulating medium, and reduces the phenomenon of local overhigh temperature caused by hysteresis loss of a special core, winding loss of a coil and medium loss of the insulating medium under high frequency. To reduce the partial discharge phenomenon, it is necessary to coat the epoxy resin with a semiconductive shield layer 401 for electrostatic isolation, which may be composed of silicon carbide SiC or graphite-modified epoxy resin.

As shown in fig. 5, for a schematic structural diagram of the primary winding provided in the embodiment of the present application, the coil is composed of a plurality of wires, and the wires are used as conductors of alternating current and need to be effectively shielded, so that the copper wire can be wound by using the semi-conductive layer to form the coil, wherein the semi-conductive layer can be a semi-conductive adhesive tape, a semi-conductive paper, or the like.

Preferably, the thickness of the semiconducting layer is between 0.05 mm and 0.2 mm, the minimum thickness of the semiconducting layer is 0.02 mm to ensure the isolating effect of the semiconducting layer, and the maximum thickness is 0.05 mm to avoid large gaps due to too thick semiconducting layers. And the casting thickness of the epoxy resin to the primary winding is between 4 mm and 12 mm, namely the minimum casting thickness is 4 mm, so as to ensure the insulation performance. And a maximum of 12 mm to reduce air bubbles.

The semi-conducting layer can be subjected to equipotential treatment with a copper wire, so that field intensity distribution is balanced, the situation of field intensity distortion is reduced, overlarge field intensity in a local place is avoided, and the phenomenon of partial discharge is effectively reduced. Similarly, the transformer obtained by packaging can perform grounding treatment on the semiconductive shielding layer on the inner surface of the packaging shell, the iron core and the semiconductive shielding layer on the surface of the winding, so that the effect of equalizing the electric field intensity can be achieved, the field intensity distortion is reduced, and the partial discharge is effectively reduced.

In the solid transformer with the structure, the primary winding is composed of the copper wire wrapped by the semi-conducting layer, the high-thermal-conductivity epoxy resin is used for pouring, the outer surface of the pouring body comprises the semi-conducting wire shielding layer, so that the conductor can be effectively isolated, the phenomenon of partial discharge is reduced, meanwhile, the insulating medium between the primary winding and the iron core is the high-thermal-conductivity epoxy resin, the heat dissipation capacity of the insulating medium can be improved while the insulating performance is ensured, and finally, softer organic silica gel is used as the insulating medium between the secondary winding and the iron core, the curing shrinkage stress is reduced while the heat dissipation capacity of the insulating medium is improved, the integrity of the iron core is included, and the working performance and the service life of the whole transformer are improved.

Next, a detailed description is given to an entire insulation packaging method of a transformer, and fig. 6 is a schematic flowchart of an insulation packaging method of a transformer according to an embodiment of the present application, where the method includes:

601. and winding the copper wire by utilizing the semi-conductive paper to obtain the primary coil.

First, a copper wire needs to be wound by using semi-conductive paper or a semi-conductive adhesive tape to obtain a primary coil, and similarly, the secondary coil may also be subjected to the same treatment to form a semi-conductive layer on the surface of the copper wire to achieve a shielding effect.

Preferably, the thickness of the semiconducting layer is between 0.02 mm and 0.05 mm, i.e. the minimum thickness of the semiconducting layer is 0.02 mm to ensure the isolating effect of the semiconducting layer, and the maximum thickness is 0.05 mm to avoid large gaps due to too thick semiconducting layers. The copper wire and the semi-conductive paper can be subjected to equipotential treatment to balance an electric field and avoid a partial discharge phenomenon caused by field intensity distortion.

602. And fixing the primary coil in a mold, and pouring the primary coil by using epoxy resin to obtain a first pouring body.

And then fixing the primary coil in a mold, and pouring the primary coil by using high-thermal-conductivity epoxy resin, wherein the thermal conductivity of the epoxy resin can be changed by adding high-thermal-conductivity filler such as boron nitride, silicon nitride, aluminum oxide, silicon oxide and the like into the epoxy resin, preferably, the thermal conductivity of the modified epoxy resin can be kept between 1.0W/(m.K) -2.0W/(m.K), the dielectric strength needs to be more than 25kV/mm, the dielectric loss is less than 0.5 percent, and the glass transition temperature Tg is more than or equal to 120 ℃.

Illustratively, the casting may be performed using a vacuum casting process, as follows:

firstly, a dry primary coil is fixed in the middle of a mould, and the whole is placed in a vacuum drying oven for heating and drying, so that bubbles and the like caused by the existence of air or liquid are reduced.

And then placing the processed primary coil and the mould into an injection pressure tank, and keeping the temperature in the injection pressure tank between 80 ℃ and 100 ℃.

And then heating the two-component epoxy resin to 70-90 ℃ respectively, preserving the heat, mixing the two-component epoxy resin with the high-thermal-conductivity filler in proportion, and performing vacuum defoaming to form the modified high-thermal-conductivity epoxy resin.

And (3) casting the primary coil by using the defoamed epoxy resin, curing (gelling) the epoxy resin at a temperature of between 80 and 100 ℃ after casting is finished, wherein the curing time is between 4 and 8 hours, and demolding the primary coil under a thermal condition.

And finally, immediately putting the cast part of the demolded primary side coil into a curing oven, keeping the curing temperature between 130 ℃ and 160 ℃, wherein the curing time is between 4 hours and 8 hours, and naturally cooling the cast part to room temperature along with the oven after the curing is finished, wherein the insulation thickness of the primary side coil is between 4 millimeters and 12 millimeters, namely the minimum insulation thickness is 4 millimeters and the maximum insulation thickness is 12 millimeters.

603. A semiconductive shield layer is formed on an outer surface of the first casting.

After the casting is completed, a semi-conductive shielding layer needs to be formed on the surface of a casting body of the primary winding for further isolation, for example, a layer of semi-conductive shielding layer can be coated in a spraying or brushing mode, the semi-conductive shielding layer can be made of silicon carbide (SiC) or graphite modified epoxy resin, the thickness of the semi-conductive shielding layer is 0.2 mm to 0.5mm, and the primary winding is finally formed. The minimum thickness of the semiconductive shielding layer is 0.2 mm, and the maximum thickness of the semiconductive shielding layer is 0.5mm, so that the optimal shielding effect is achieved. The structure of the first casting body can refer to the structure of the embodiment shown in fig. 4, and is not described herein again.

604. And assembling the iron core, the secondary winding and the first casting body.

After the first casting body is obtained, the first casting body, the secondary winding and the iron core need to be assembled, and according to the electromagnetic induction principle of the transformer, the middle iron core needs to penetrate through the secondary winding and the primary winding.

605. And forming a semiconductor shielding layer on the inner surface of the packaging shell, and putting the assembled iron core, the secondary winding and the first pouring body into the packaging shell.

Specifically, a layer of semiconductive shielding layer can be coated on the inner surface of the packaging shell by spraying or brushing, and the thickness of the semiconductive shielding layer is between 0.2 and 0.5mm, so as to further perform isolation. And (4) putting the assembled iron core, the secondary winding and the first casting body into a packaging shell.

606. And (4) pouring the assembled packaging shell, the first pouring body, the iron core and the secondary winding into a whole by using organic silica gel to obtain the transformer.

And pouring the assembled shell, the primary winding, the iron core and the secondary winding by using the organic silicon adhesive which is strong in heat-conducting property and soft in material to obtain the final transformer. The organic silica gel with high thermal conductivity can be bi-component addition type organic silica gel, in a preferable scheme, the thermal conductivity coefficient of the organic silica gel for pouring is not lower than 2.0W/(m.K), the dielectric strength is more than or equal to 15kV/mm, and the pouring whole body can be formed in a vacuum encapsulation mode.

Specifically, the two-component organic silicon potting adhesive can be mixed in proportion, defoaming treatment is carried out in vacuum, and then the assembled transformer body is placed in a vacuum potting box, and pressure is maintained for 5 to 10 minutes. And (3) carrying out vacuum encapsulation after pressure maintaining is finished, immediately transferring the body into an oven after encapsulation is finished, keeping the temperature of the oven between 60 ℃ and 70 ℃, baking for 30 minutes to 60 minutes, and taking out the body after the organic silicon pouring sealant is cured.

According to the transformer obtained by the method, the primary winding is composed of the copper wire wrapped by the semi-conducting layer, the high-thermal-conductivity epoxy resin is used for pouring, the outer surface of the pouring body comprises the semi-conducting wire shielding layer, so that the conductor can be effectively isolated, the phenomenon of partial discharge is reduced, meanwhile, the insulating medium between the primary winding and the iron core is the high-thermal-conductivity epoxy resin, the heat dissipation capacity of the insulating medium can be improved while the insulating performance is guaranteed, and finally, the softer organic silica gel is used as the insulating medium between the secondary winding and the iron core, the curing shrinkage stress is reduced while the heat dissipation capacity of the insulating medium is improved, the integrity of the iron core is included, and the working performance and the service life of the whole transformer are improved.

The solid-state transformer can be applied to various active circuits to realize the conversion of electric energy, and the stability of the active circuits can be improved because the solidified transformer is stable and has good electrical performance.

Technical terms used in the embodiments of the present invention are only used for illustrating specific embodiments and are not intended to limit the present invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Further, the use of "including" and/or "comprising" in the specification is intended to specify the presence of stated features, integers, steps, operations, elements, and/or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, and/or components.

The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below, if any, are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed.

Claims

1. A transformer, comprising: the primary winding, the secondary winding, the iron core and the packaging shell;

the iron core penetrates through the primary winding and the secondary winding;

the primary winding is poured by epoxy resin to form a first pouring body;

the secondary winding, the first casting body and the iron core are cast into a whole by organic silica gel to form a second casting body;

the packaging shell is used for packaging the second casting body, wherein the inner surface of the packaging shell is coated with a semi-conductive shielding layer.

2. The transformer of claim 1, wherein an outer surface of the first casting is coated with the semiconducting shield layer.

3. The transformer of claim 2, wherein the primary winding is comprised of a copper wire and a semiconducting layer; the semi-conducting layer is wound on the outer side of the copper wire.

4. A transformer according to claim 3, characterized in that the semiconducting layer is equipotential with the copper wire.

5. A transformer according to claim 3, characterized in that the thickness of the semiconducting layer is between 0.05 mm and 0.2 mm.

6. The transformer of any of claims 2 to 5, wherein the epoxy is cast to a thickness of between 4 mm and 12 mm over the primary winding.

7. The transformer of any one of claims 1 to 6, wherein the thickness of the semiconducting shield is between 0.2 mm and 0.5 mm.

8. The transformer according to any one of claims 1 to 7, wherein the epoxy resin and the silicone rubber each have high thermal conductivity.

9. An insulation packaging method for a transformer, the method comprising:

winding a copper wire by using semi-conductive paper to obtain a primary winding;

fixing the primary winding in a mold, and pouring the primary winding by using epoxy resin to obtain a first pouring body;

forming a semiconductive shield layer on an outer surface of the first casting;

assembling an iron core, a secondary winding, and the first casting such that the iron core passes through the secondary winding and the first casting;

pouring the assembled iron core, the secondary winding and the first pouring body into a whole by using organic silica gel to obtain a second pouring body;

10. The method of claim 9, wherein the semiconducting paper is equipotential with the copper wire.

11. A method according to claim 9 or 10, characterized in that the thickness of the semiconducting paper is between 0.05 mm and 0.2 mm.

12. The method of any of claims 9 to 11, wherein the epoxy is cast to a thickness of between 4 mm and 12 mm on the primary winding.

13. A method according to any of claims 9 to 12, wherein the thickness of the semiconducting shield is between 0.2 mm and 0.5 mm.

14. The method according to any one of claims 9 to 13, wherein the epoxy resin and the silicone gel each have high thermal conductivity.

15. An active circuit, characterized in that it comprises a transformer according to any one of claims 1 to 8.