In the vast network of modern power systems, transformers, as key equipment, are like energy hubs that bear the heavy responsibility of voltage conversion. Among them, dry-type transformers, with their unique structure and performance characteristics, have emerged in many application scenarios and become an indispensable and important role in the power sector. From high-rise buildings in bustling cities to data centers full of technology, from busy industrial plants to municipal facilities related to people's livelihood, dry-type transformers are everywhere, silently escorting stable and reliable power supply. It is not only a core component in the process of power transmission and distribution, but also an important force in promoting the development of the power industry towards efficiency, safety and environmental protection.
1. The development history of dry-type transformers
The development history of dry-type transformers is a history of technological evolution with continuous innovation and breakthroughs. In the 1960s, dry-type transformers ushered in a milestone development stage. In 1964, the German AEG company successfully developed the first 400kVA/20kV epoxy cast dry-type transformer. This achievement was like a heavy bomb in the field of power equipment, opening up a new path for the development of dry-type transformers. At the same time, the United States discovered Nomex insulation paper. This high-performance insulation material laid the foundation for the birth of H-class dry-type transformers. Since then, dry-type transformers have gradually formed two major categories: one is epoxy dry-type transformers with epoxy resin as the main insulation material; the other is Nomex paper dry-type transformers with Nomex paper as the insulation material.
In the following decades, dry-type transformers have developed rapidly around the world. In developed countries such as Europe and the United States, the technology of dry-type transformers has been continuously innovated, and the output has also increased year by year. So far, in the distribution transformer market in these countries, the output of dry-type transformers has exceeded 20%. In the field of complete substations, dry-type transformers occupy 80%-90% of the market share, becoming an absolute mainstream product.
my country's dry-type transformer development has also achieved remarkable results. In 1966, Shenyang Transformer Factory successfully developed the ZSG-1800/10 guided air-cooled H-class dry-type transformer, and Shanghai Transformer Factory also successfully developed the SG3-800/10/1.2/0.4 three-coil self-cooled H-class dry-type transformer, which took a solid first step in the development of my country's dry-type transformers. In the late 1970s, Shanghai Transformer Factory independently designed and developed the SCL-630 epoxy cast transformer, which further promoted the progress of my country's dry-type transformer technology. Since the second urban power grid transformation meeting in 1989, with the rapid development of my country's economy and the continuous growth of electricity demand, the output of dry-type transformers has shown explosive growth. Since the 1990s, it has increased by about 20% every year. In 1999, the total output of dry-type transformers in my country has approached 10,000 MVA, far exceeding the forecast 10 years ago. By 2002, the total output reached 20,000 MVA, and in 2004 it reached 32,000 MVA. Today, my country has deservedly become one of the countries with the largest production and sales of dry-type transformers in the world, and is at the world's leading level in terms of factory scale, product capacity, voltage level, etc.
2. The working principle is revealed

(I) The magical application of the law of electromagnetic induction
The working principle of dry-type transformers is based on the law of electromagnetic induction. This important law in physics provides a theoretical basis for transformers to achieve voltage conversion. When an alternating current passes through the primary winding of a dry-type transformer, an alternating magnetic field is generated around the winding. This alternating magnetic field is like an active energy carrier that passes through the iron core and induces an electromotive force in the secondary winding. According to the law of electromagnetic induction, the magnitude of the induced electromotive force is proportional to the rate of change of the magnetic flux passing through the winding. Since the primary winding and the secondary winding surround the same iron core, they are in the same alternating magnetic field. Therefore, there is a specific proportional relationship between the electromotive force induced in the secondary winding and the voltage of the primary winding. This proportional relationship is the transformation ratio of the transformer. By reasonably designing the turns ratio of the primary winding and the secondary winding, the dry-type transformer can increase or decrease the input voltage to the required output voltage, thereby meeting the needs of different electrical equipment.
(II) The specific process of voltage conversion
In a dry-type transformer, after the primary winding is connected to the AC power supply, the current flows in the winding, and the generated magnetic field forms a closed loop along the iron core. As a good magnetic conductive material, the iron core can effectively concentrate and guide the magnetic field, reduce the leakage of magnetic flux, and improve the working efficiency of the transformer. With the periodic changes of the AC power supply, the magnitude and direction of the current in the primary winding are constantly changing, which makes the strength and direction of the magnetic field change synchronously. When the changing magnetic field passes through the secondary winding, according to the principle of electromagnetic induction, an induced electromotive force will be generated in the secondary winding. If the secondary winding is connected to a load, then under the action of the induced electromotive force, a current will flow through the load, thereby realizing the transmission of electric energy and voltage conversion. For example, in a step-down dry-type transformer, the primary winding has more turns and the secondary winding has fewer turns. According to the ratio relationship, when the primary winding is connected to a higher voltage power supply, a lower voltage will be induced in the secondary winding, providing a suitable power supply for low-voltage electrical equipment.
3. Unique structural features
(I) Exquisite design of the core structure
Selection of high-quality materials: The core of the dry-type transformer usually uses high-magnetic permeability high-quality grain-oriented cold-rolled silicon steel sheets. This material has extremely high magnetic permeability and can generate a large magnetic flux under a small magnetic field intensity, thereby effectively reducing the hysteresis loss and eddy current loss in the core. At the same time, the resistivity of the silicon steel sheet is relatively high, which can reduce the heat generated by the eddy current in the core and improve the operating efficiency and stability of the transformer.
45-degree full-slant joint technology: In order to further optimize the performance of the core, the core silicon steel sheet of the dry-type transformer adopts a 45-degree full-slant joint method. This joint method enables the magnetic flux to pass smoothly along the joint direction of the silicon steel sheet, reducing the sudden change and leakage of the magnetic flux at the joint, and reducing the no-load loss and no-load current of the core. Compared with the traditional butt joint method, the 45-degree full-bevel joint technology can significantly improve the magnetic permeability of the core, making the transformer more efficient and stable during operation. At the same time, it can also reduce the noise generated by the core and improve the operation quality of the transformer.
(II) Diversity of winding structure
Solid insulation encapsulated winding: In some dry-type transformers, the winding is encapsulated by solid insulation. This structure usually involves casting and encapsulating the winding with insulating materials such as epoxy resin to form a solid whole. The solid insulation encapsulated winding has good electrical insulation performance and mechanical strength, and can effectively protect the winding from the influence of the external environment, such as dust and moisture. At the same time, insulating materials such as epoxy resin also have good heat dissipation performance, which can dissipate the heat generated by the winding in time to ensure the normal operation of the transformer.
Unencapsulated winding: In addition to solid insulation encapsulated winding, there is also a structure of unencapsulated winding. Unencapsulated windings generally use special insulating paper to insulate the winding, and then impregnate it with special insulating paint. The winding of this structure has better heat dissipation performance, because the contact area between the winding and the air is large, and air convection can be used more effectively to dissipate heat. The manufacturing process of the unencapsulated winding is relatively simple and low-cost, which is suitable for some cost-sensitive applications.
Winding form segmentation:
Wound winding: This winding form is to tightly wind the wire on the iron core according to certain rules. Wound winding has high mechanical strength and electrical insulation performance, and can adapt to higher voltage and current requirements. In some small dry-type transformers, wound winding is widely used.
Epoxy resin plus quartz sand filling casting winding: By adding filling materials such as quartz sand to epoxy resin and then casting the winding, the mechanical strength and heat dissipation performance of the winding can be improved. Quartz sand has a high thermal conductivity, which can effectively conduct the heat generated by the winding, and at the same time increase the hardness and wear resistance of the winding.
Glass fiber reinforced epoxy resin casting winding (thin insulation structure): This winding structure uses glass fiber to reinforce epoxy resin to form a thin insulation layer. Glass fiber can enhance the mechanical properties of epoxy resin, making it more resistant to stretching and impact. The thin insulation structure can reduce the amount of insulation material used, reduce the volume and weight of the transformer, and improve the space utilization of the transformer while ensuring the electrical insulation performance.
Multi-strand glass fiber impregnated with epoxy resin wound winding: Multi-strand glass fiber impregnated with epoxy resin and wound on the winding can effectively prevent the cast resin from cracking and improve the reliability of the equipment. Glass fiber has good flexibility and insulation performance, and can form a solid protective barrier on the surface of the winding to enhance the electrical insulation performance and mechanical strength of the winding.
(III) Other key structural components

Insulation cylinder and pad: An insulation cylinder is usually placed between the high and low voltage coils of the dry-type transformer. The function of the insulation cylinder is to increase the electrical insulation distance between the high and low voltage coils to prevent electrical breakdown accidents. At the same time, the pad is used to support and constrain the coil to ensure that the coil maintains a stable position during operation and avoid displacement or deformation due to vibration or electromagnetic force. A pressure nail structure is used between the pad and the clamp, and a silicone rubber plate is used to press the pad and the winding to form an elastic buffer structure. This structure can effectively absorb the expansion and contraction of the iron core, ensure that the entire body is always in a compressed state, and reduce the noise generated by the resonance between the winding and the iron core.
Anti-loosening design of fasteners: The fasteners of the overlapped parts of the dry-type transformer have anti-loosening properties. This is because during the operation of the transformer, it will be affected by various factors such as electromagnetic force and vibration. If the fasteners are loose, it may cause unstable connections between parts, affect the normal operation of the transformer, and even cause safety accidents. Therefore, by adopting special anti-loosening designs, such as using anti-loosening nuts, spring washers, etc., it can ensure that the fasteners are always tightened during long-term operation, improving the reliability and safety of the transformer.
IV. Excellent performance advantages
(I) High safety: escort for power safety
Excellent fire and explosion resistance: One of the biggest safety advantages of dry-type transformers is that they do not use insulating oil. In traditional oil-immersed transformers, insulating oil is a potential risk source for fire and explosion. Dry-type transformers use air as the cooling medium, and the windings and cores are not immersed in insulating oil, which fundamentally eliminates safety accidents caused by insulating oil leakage, combustion or explosion. This feature makes dry-type transformers particularly suitable for use in places with extremely high requirements for fire and explosion resistance, such as high-rise buildings, subways, hospitals, schools, shopping malls and other crowded public areas, as well as flammable and explosive industrial environments such as chemicals and petroleum. In these places, once a fire or explosion accident occurs, the consequences will be disastrous, and the application of dry-type transformers provides a reliable guarantee for the power safety of these places.
No toxic substance release: In addition to fire and explosion resistance, dry-type transformers do not release any toxic substances during operation. Unlike some electrical equipment that may produce toxic gases during failure or aging, the insulation materials and other components of dry-type transformers will not cause harm to the environment and human health under normal use and abnormal conditions. This not only meets the strict requirements of modern society for environmental protection and health, but also makes dry-type transformers widely used in various places that are sensitive to environmental and personnel safety. For example, in food processing plants, pharmaceutical plants and other enterprises with extremely high requirements for sanitary conditions, dry-type transformers can ensure that the production environment is not polluted, and ensure product quality and the health of employees.
(II) Easy maintenance: Reduce operation and maintenance costs
Reduce regular maintenance work: Since dry-type transformers do not require the use of insulating oil, there is no need for tedious maintenance work such as regular oil quality testing, replacement of insulating oil or treatment of oil pollution like oil-immersed transformers. This greatly reduces the maintenance workload and maintenance frequency of transformers, allowing operation and maintenance personnel to devote more time and energy to other important power equipment maintenance work. For example, in a large substation with multiple transformers, if dry-type transformers are used, a lot of time and manpower costs can be saved every year for maintenance work related to insulating oil.
Easy to diagnose and repair faults: The structure of dry-type transformers is relatively simple, and key components such as windings and cores can usually be directly observed and touched. This enables operation and maintenance personnel to diagnose and locate faults more quickly and accurately when a transformer fails. In contrast, the internal structure of oil-immersed transformers is complex, and fault troubleshooting is more difficult. For example, when the winding of a dry-type transformer has problems such as local overheating or insulation damage, the operation and maintenance personnel can quickly find the problem through visual inspection or use simple detection equipment, and take corresponding repair measures, which greatly shortens the fault handling time and improves the reliability and availability of the power system.
(III) Excellent environmental performance: practicing the concept of green development
No oil pollution problem: As mentioned above, dry-type transformers do not use insulating oil, which avoids the pollution of soil, water sources and air caused by insulating oil leakage. During the use of oil-immersed transformers, once an insulating oil leakage accident occurs, the cleaning and repair work is not only costly, but also the damage to the environment may be long-term. The application of dry-type transformers solves this environmental problem from the source, meets the requirements of sustainable development, and has made positive contributions to the protection of the ecological environment. In some areas with extremely strict requirements on the ecological environment, such as nature reserves, scenic spots, etc., dry-type transformers have become the preferred equipment for power supply.
Wide application of recyclable materials: Recyclable materials are widely used in the design and manufacturing process of dry-type transformers. For example, the silicon steel sheets of the core and the steel of the shell can be recycled and reused after the service life of the transformer ends, which reduces the generation of waste and the consumption of natural resources. At the same time, some insulating materials used in dry-type transformers, such as Nomex paper, do not release toxic substances when burned, and some insulating materials can also be naturally degraded, further reducing the impact on the environment. This design concept that focuses on environmental protection throughout the entire life cycle makes dry-type transformers a model of green development in the power sector.
(IV) Strong adaptability: Coping with diverse application scenarios
Adapt to different environmental conditions: Through special design and process treatment, the windings of dry-type transformers can have good moisture resistance and anti-fouling performance. This enables it to operate stably in dusty, humid industrial environments and other harsh natural environments. For example, in some places with severe dust pollution such as mines and cement plants, as well as places with high air humidity such as coastal areas, dry-type transformers can work normally, providing reliable power support for industrial production and residents' lives in these areas. Dry-type transformers can also be equipped with shells with different protection levels, such as IP20, IP30, etc., to adapt to different use environment requirements. The shell with a higher protection level can effectively prevent dust, water droplets and other foreign objects from entering the transformer and protect the normal operation of the transformer.

Installed at the load center: The small size and light weight of dry-type transformers allow them to be installed directly near the center of the load. The advantage of doing so is that it can greatly reduce the loss of electric energy during transmission and improve the operating efficiency of the power system. In some large commercial buildings or industrial plants, installing dry-type transformers near the electrical shaft or equipment on each floor can shorten the length of the power transmission line, reduce the power loss caused by line resistance, and reduce voltage drop, ensure voltage stability at the load end, and improve the working performance of electrical equipment.
(V) Significant energy-saving effect: Help energy conservation and emission reduction
Low loss characteristics: Dry-type transformers use advanced core materials and winding designs, with low no-load loss and load loss. For example, some new dry-type transformers reduce no-load loss by 20% - 30% compared with traditional transformers by optimizing the magnetic permeability of the core and the turns ratio of the winding, and the load loss is also significantly reduced. In the power system, the loss of the transformer is an important part of the power consumption. The low loss characteristics of the dry-type transformer can effectively reduce energy waste and contribute to energy conservation and emission reduction.
Low noise operation: During operation, the dry-type transformer generates low noise. This is due to its reasonable core structure design and advanced manufacturing process, which effectively reduces the vibration and noise generated by the core and winding under the action of electromagnetic force. For some places with high requirements for noise environment, such as schools, hospitals, residential areas, etc., low-noise dry-type transformers can meet the needs of these places for a quiet environment and avoid interference to surrounding residents and staff caused by transformer noise. For example, the use of low-noise dry-type transformers in the power distribution system of a hospital can ensure the quietness of the internal environment of the hospital without affecting the treatment and rest of patients.

V. Application fields of dry-type transformers

(I) Core applications in power systems

Wide application in power generation links: In the field of power generation, dry-type transformers play an important role in various forms of power generation such as wind power, photovoltaic power, thermal power, hydropower, and nuclear power. Especially in the field of high-power wind turbines and offshore wind power, dry-type transformers have become key equipment for connecting wind turbines to power grids due to their good moisture resistance and ability to adapt to harsh environments. In the photovoltaic field, dry-type transformers are mainly used in photovoltaic power stations and photovoltaic industry chains, especially in some special scenarios with harsh environments or high fire protection requirements, such as photovoltaic power stations in desert areas. Dry-type transformers can operate stably to ensure the efficient conversion and transmission of photovoltaic power.
The key role of power transmission and distribution: In the process of power transmission and distribution, dry-type transformers undertake the important tasks of voltage conversion and power isolation. In urban power grids, dry-type transformers reduce the voltage of high-voltage transmission lines to low voltage suitable for residents and enterprises, providing a stable and reliable power supply for the normal operation of the city. In some large factories, mines and other industrial sites, dry-type transformers perform precise voltage conversion according to the voltage requirements of different production equipment to ensure the smooth progress of industrial production. At the same time, the electrical isolation performance of dry-type transformers can effectively protect the safety of electrical equipment and personnel and prevent electrical accidents.
(II) Deep penetration in the industrial field
Manufacturing: In manufacturing enterprises such as automobile manufacturing, mechanical processing, and electronic equipment manufacturing, dry-type transformers are widely used in the power system of workshops. These enterprises have a wide variety of production equipment and high requirements for power quality and stability. Dry-type transformers can provide stable voltage and sufficient power supply according to the power demand of different equipment, ensure the normal operation of production equipment, and improve production efficiency and product quality. For example, in automobile production lines, a large number of automation equipment and precision instruments require stable power support. Dry-type transformers ensure the continuous and efficient operation of the production line through reasonable voltage regulation and power distribution.
Petrochemical: The petrochemical industry is flammable and explosive, and has complex environment, and has extremely strict requirements on the safety and reliability of power equipment. Since dry-type transformers do not use insulating oil, they have fireproof and explosion-proof characteristics, which can effectively reduce the risk of fire and explosion and meet the special safety needs of petrochemical enterprises. At the same time, dry-type transformers also have good corrosion resistance and can adapt to various corrosive gas and liquid environments in the petrochemical production process, ensuring the stability of power supply and ensuring the safe conduct of petrochemical production. In refineries, chemical plants and other places, dry-type transformers provide power for various production equipment, pumps, compressors and other equipment, and are indispensable and important equipment for petrochemical production.
Mining: The mining environment is harsh, with problems such as humidity, dust, and high vibration, which ordinary power equipment finds difficult to adapt to. Dry-type transformers have become the preferred equipment for mine power systems due to their resistance to moisture, dirt and vibration. In mines, dry-type transformers are used to provide power for mining equipment, lifting equipment, ventilation equipment, etc. to ensure the smooth progress of mining operations. In addition, the small size and light weight of dry-type transformers also make them easy to install and transport under the complex terrain conditions of mines.
(III) Important support for commercial and civil buildings
High-rise buildings: With the acceleration of urbanization, high-rise buildings have sprung up like mushrooms after rain. In high-rise buildings, dry-type transformers have an irreplaceable position. Due to the dense population in high-rise buildings, the requirements for fire safety are extremely high. The fireproof and explosion-proof characteristics of dry-type transformers can effectively protect the safety of people and property in the building. At the same time, dry-type transformers can be installed in limited space locations such as basements or floor distribution rooms of buildings, saving valuable building space. In addition, the low-noise operation characteristics of dry-type transformers will not interfere with the living and working environment of residents in high-rise buildings. For example, in high-rise buildings such as office buildings, hotels, and apartments in cities, dry-type transformers provide a stable power supply for elevators, lighting, air conditioning, water supply and drainage systems to ensure the normal use of the building.
Commercial complexes: Commercial complexes integrate multiple functions such as shopping, catering, entertainment, and office, with many electrical equipment, large power loads, and complex changes. Dry-type transformers can flexibly configure capacity and voltage levels according to the power demand of different areas of the commercial complex to achieve efficient power distribution. At the same time, dry-type transformers are highly intelligent and can monitor the power operation status in real time through intelligent control systems, adjust power supply in time, optimize energy utilization efficiency, and reduce operating costs. In large shopping malls, cinemas, restaurants and other places in commercial complexes, dry-type transformers provide stable and reliable power for various lighting fixtures, refrigeration equipment, elevators and escalators, electronic display screens, etc., creating a comfortable shopping and consumption environment.
Hospitals: Hospitals are places for saving lives and healing the wounded, and have extremely high requirements for the continuity and stability of power supply. Any power outage may endanger the life safety of patients. Dry-type transformers have the characteristics of high reliability and easy maintenance, which can ensure the stable operation of hospital power systems. At the same time, dry-type transformers have good environmental performance and will not pollute the medical environment of hospitals. In hospitals, dry-type transformers provide power for key areas such as operating rooms, intensive care units (ICUs), and medical equipment rooms to ensure the normal operation of various precision medical equipment, such as CT scanners, magnetic resonance imaging (MRI) equipment, and electrocardiogram monitors. In addition, the intelligent monitoring function of dry-type transformers can also monitor power parameters in real time, detect potential faults in a timely manner, and provide strong protection for the power safety of hospitals.
Schools: Schools are the cradles for cultivating talents and require a quiet and safe learning and living environment. The low-noise operation and fireproof and explosion-proof characteristics of dry-type transformers are very suitable for the application needs of schools. In school buildings, libraries, laboratories, student dormitories and other places, dry-type transformers provide stable power supply for lighting, teaching equipment, air conditioning, networks and other systems to ensure the normal development of teaching activities. At the same time, the intelligent management function of dry-type transformers can also realize the reasonable allocation and effective monitoring of school power resources, improve energy utilization efficiency, and reduce school electricity costs.
(IV) Power supply guarantee for data centers
Data centers are the core infrastructure of modern information technology, carrying a large amount of data storage, processing and transmission tasks, and the requirements for the stability and reliability of power supply have reached the extreme. Dry-type transformers have become key equipment in the power system of data centers with their high efficiency, energy saving and reliability. In data centers, dry-type transformers provide stable power supply for servers, network equipment, refrigeration equipment, etc. to ensure the normal operation of data centers. At the same time, the intelligent management system of dry-type transformers can monitor the power operation status in real time, automatically adjust the power output according to the load changes of the data center, and achieve optimal utilization of energy. In addition, the modular design and flexible configuration capabilities of dry-type transformers can also meet the needs of continuous expansion and upgrading of data centers, providing strong support for the sustainable development of data centers.
(V) Application in the field of rail transportation
Metro and light rail: As an important part of urban public transportation, subways and light rails have the advantages of large capacity, fast speed and punctuality. In subway and light rail systems, dry-type transformers are widely used in traction power supply systems, power lighting systems, etc. In the traction power supply system, dry-type transformers convert the high-voltage electricity of the power grid into low-voltage direct current suitable for the operation of subway trains to provide power for the trains. In the power lighting system, dry-type transformers provide power for the lighting, ventilation, air conditioning, elevators and other equipment of the station to ensure the normal operation of the station and the comfortable travel of passengers. The fireproof and explosion-proof, moisture-proof and dust-proof, vibration-resistant and other characteristics of dry-type transformers can adapt to the complex underground environment and small space of subways and light rails, ensuring the safety and reliability of power supply.
Railway: In the field of railway transportation, dry-type transformers also play an important role. In substations, signal stations, communication base stations and other places along the railway, dry-type transformers are used to provide power for railway signal equipment, communication equipment, power supply equipment, etc. Railway transportation has extremely high requirements for the accuracy and reliability of signals and communications. Any power failure may cause train operation interruption or safety accidents. The high reliability and stability of dry-type transformers can provide stable power guarantee for railway signal and communication systems, ensuring the safe and punctual operation of trains. At the same time, the energy-saving and environmental protection characteristics of dry-type transformers also meet the requirements of green development of the railway transportation industry, which helps to reduce energy consumption and environmental pollution in railway operations.