Introduction:
A transformer operates based on the principle of electromagnetic induction. The transformer body mainly consists of windings and a core. During operation, the windings serve as the path for “electricity,” while the core serves as the path for “magnetism.”
When electrical energy is supplied to the primary side, its alternating nature generates an alternating magnetic field in the core (that is, electrical energy is converted into magnetic energy). As the magnetic flux linking the secondary winding changes continuously, an electromotive force is induced in the secondary winding. When the external circuit is connected, electrical energy is delivered to the load (that is, magnetic energy is converted back into electrical energy).
This “electricity–magnetism–electricity” conversion process is achieved based on the principle of electromagnetic induction, and this energy conversion process is the working process of a transformer.
Simply put, a dry-type transformer is a power transformer in which the core and coils are not immersed in an insulating liquid (insulating oil).
It mainly consists of a core made of silicon steel sheets and coils cast with epoxy resin. An insulating cylinder is placed between the high-voltage and low-voltage coils to increase electrical insulation, while spacers are used to support and restrain the coils.
CHBEB GROUP has focused on transformer manufacturing for 60 years. Its products cover various types of transformers, including oil-immersed transformers and dry-type transformers, meeting the needs of industrial, renewable energy, power distribution, and other application scenarios. Click the link to learn more about our dry-type transformers.
Epoxy resin cast dry-type transformers are important power equipment in distribution systems. Since epoxy resin is a flame-retardant, fire-resistant, and self-extinguishing solid insulating material, it is both safe and clean. Therefore, epoxy resin cast dry-type transformers are widely used because of their oil-free design, flame resistance, low operating losses, and strong disaster resistance.
Compared with oil-immersed transformers, dry-type transformers do not contain oil, so there are no issues such as fire, explosion, or pollution. Losses and noise are also reduced to a new level, creating better conditions for transformers and low-voltage panels to be installed in the same distribution room.
A dry-type transformer mainly consists of a core and windings. The windings are divided into high-voltage windings and low-voltage windings.
The core adopts a 45° fully mitered joint structure. The joints between the core limbs and yokes use a five-step single-sheet stacking structure, which helps improve the magnetic field distribution at the joints.
The core limbs are automatically stacked and formed, effectively reducing the burr height of the core laminations and ensuring the dimensional accuracy of the core sheets. Channel-steel clamps are used, providing high rigidity, good core appearance, and excellent mechanical strength. The upper and lower yokes are secured by four through-core bolts to ensure uniform clamping force. After the transformer coils are assembled onto the core, they form an integrated structure with good overall stability.
The surface of the transformer core is coated with an epoxy resin-based coating that provides rust prevention, moisture resistance, and protection against condensation on the core surface. Metal components and all standard fasteners are also treated with surface anti-rust protection.
The epoxy resin casting of the high-voltage coil adopts static mixing technology. After winding, the high-voltage coil is preheated and then transferred into the casting chamber of the epoxy resin vacuum casting equipment for vacuum drying to remove moisture and gases from the insulating materials.
Epoxy resin, curing agent, and other chemical materials are vacuum-degassed separately. According to the ratio, weight, and speed set by the computer control software based on process requirements, the materials are pumped through metering pumps into a static mixer. After being thoroughly mixed, they are injected into the coil with the mold. Finally, the cast coil is heated and cured.
The low-voltage coil of the transformer adopts a foil-wound structure with resin-sealed ends, and pre-impregnated epoxy resin F-class insulated DMD composite foil is used as the interlayer insulation.
After thermal curing, the coil becomes a completely rigid structure, which helps balance the magnetomotive force between the high-voltage and low-voltage coils and improves the dynamic stability of the transformer. It can also effectively reduce eddy current losses in the low-voltage valve-side coil.
Other Accessories
Temperature Controller
The temperature sensors can monitor the temperatures of the three-phase windings and the core in real time. The system provides functions such as winding overtemperature alarm, winding excessive-temperature trip, core excessive-temperature alarm, and enclosure door opening monitoring.
The information can also be transmitted to the substation integrated automation system through a remote communication interface. In the event of loss of power or device failure, a hard-contact signal output is provided.
Enclosure
According to the characteristics of the operating environment and protection requirements, different enclosures can be selected for dry-type transformers.
An IP23 protective enclosure is commonly used. It can prevent solid foreign objects larger than 12 mm in diameter, as well as small animals such as rats, snakes, cats, and birds, from entering and causing serious faults such as short circuits and power outages, while also providing a safety barrier for live parts.
If the transformer needs to be installed outdoors, an IP23 protective enclosure can be selected. In addition to the above-mentioned IP20 protection functions, it can also prevent water droplets falling at an angle of up to 60° from the vertical from entering.
However, an IP23 enclosure will reduce the cooling capacity of the transformer, so the reduction in operating capacity should be taken into account when selecting it.
The working principle of a transformer is based on the principle of electromagnetic induction. Through electromagnetic induction, electrical energy is transferred between two circuits.
The core is a closed magnetic circuit. After the primary winding is connected to the power supply, the alternating current produces an alternating magnetic flux in the core. The alternating magnetic flux induces an AC electromotive force in both the primary and secondary windings. The magnitude of the electromotive force is proportional to the rate of change of the magnetic flux and the number of turns of the corresponding winding. The ratio of the primary-side voltage to the secondary-side voltage is approximately equal to the turns ratio.
By changing the number of turns in the secondary winding, the output voltage can be changed.
In recent years, dry-type transformers have developed rapidly. The main reason is that they have characteristics that traditional oil-immersed transformers do not have: good flame-retardant and safety performance, allowing installation at load centers; light weight and small size, making installation convenient; low energy consumption and high efficiency; no pollution and easy maintenance; moisture resistance and heat resistance; high mechanical strength and resistance to cracking; and low partial discharge.
During operation, the core components of a dry-type transformer, the core and windings, are not immersed in insulating oil, but rely only on air convection for cooling. This determines that dry-type transformers have relatively low requirements for constant temperature. Furthermore, apart from the lubrication necessary for equipment operation, dry-type transformers that do not rely on oil immersion basically have no risks of fire or explosion, and there is no disadvantage of environmental pollution, so they do not need to be placed in a separate room. In addition, dry-type transformers also feature low-loss and low-noise operation. However, because of their small size and light weight, additional reinforcement is required during installation.
Dry-type transformers and oil-immersed transformers operate on the same principle. The main difference is whether there is oil inside the transformer. They also differ in the following aspects:
| Comparison Point | Key Differences |
|---|---|
| Appearance | From the appearance, the enclosure form is different. The core and coils of a dry-type transformer can be seen directly, while an oil-immersed transformer only shows the transformer enclosure. |
| Lead-Out Form | The lead-out form is different. Dry-type transformers mostly use silicone rubber bushings, while oil-immersed transformers mostly use porcelain bushings. |
| Capacity and Voltage Levels | The capacity and voltage levels are different. Dry-type transformers are generally used for power distribution, with capacities usually below 2000 kVA and voltage levels below 35 kV, although some can reach 110 kV. Oil-immersed transformers, however, can cover the full range of capacities from small to large, and can also cover all voltage levels. |
| Insulation and Heat Dissipation | The insulation and heat dissipation methods are different. Dry-type transformers generally use resin insulation and rely on natural air cooling, while larger-capacity units use fans for cooling. Oil-immersed transformers use insulating oil for insulation, and the insulating oil circulates inside the transformer to transfer the heat generated by the coils to the transformer radiators for heat dissipation. |
| Application Locations | In terms of application locations, dry-type transformers are mostly used in places requiring “fire prevention and explosion prevention,” and are commonly used in large buildings and high-rise buildings. Oil-immersed transformers, because oil may spray out or leak in the event of an accident and cause a fire, are mostly used outdoors and in locations where an emergency oil pit can be provided. |
| Load-Bearing Capability | The load-bearing capability is different. Generally, dry-type transformers should operate at rated capacity, while oil-immersed transformers have better overload capability. |
| Cost | The cost is also different. For transformers of the same capacity, the purchase price of a dry-type transformer is much higher than that of an oil-immersed transformer. |
Choosing the right power transformer supplier not only affects equipment performance, but also directly influences the safety and economic efficiency of the power system. So, how can you choose a truly reliable transformer manufacturer? As a transformer manufacturer with more than 60 years of production history, CHBEB GROUP has summarized the following criteria based on our experience and practice.
A reliable transformer manufacturer must first operate legally and compliantly and obtain recognition from authoritative certification systems. This is important evidence of the company’s strength and product quality, and it is also a prerequisite for participating in major project tenders.
CHBEB GROUP has advanced production and testing equipment, comprehensive testing processes, and a modern management system. We adhere to innovative development and have passed ISO9001 Quality Management System Certification, ISO14000 Environmental Management System Certification, ISO45001 Occupational Health and Safety Management System Certification, CE Conformity Report, Low Voltage Directive Conformity, and GOST Declaration of Conformity, to meet the requirements of different markets and projects.
The technical advancement of transformers is directly related to the operating efficiency and stability of a project over the coming decades. A reliable manufacturer must have solid technical expertise and advanced product support.
As a National High-Tech Enterprise, CHBEB GROUP has certification from the National Transformer Quality Supervision and Inspection Center, CCC certification, 5 invention patents, and more than 120 patent certifications.
We provide high-quality products and solutions for State Grid Corporation of China and industries around the world, including power, metallurgy, steel, petrochemical, machinery manufacturing, and pharmaceuticals.
During 60 years of development, CHBEB GROUP has established its Beijing headquarters as the center for technical research and development, with three major production industrial parks in Nanjing, Jiangsu and Yueqing, Zhejiang. The company specializes in the production of transformers, compact substations, wind power substations, solar photovoltaic substations, high- and low-voltage switchgear assemblies, ring main units, pole-mounted outdoor circuit breakers, outdoor vacuum circuit breakers, power transmission and distribution supporting equipment, as well as power engineering contracting and installation.
A high-quality transformer product depends not only on reliable raw materials, but also on strict control of every production process.
CHBEB has always attached great importance to quality control throughout the entire production process and insists on working with leading raw material suppliers in the industry. From silicon steel sheets, copper wire, and insulation materials to transformer electrical accessories, product quality and stability are ensured from the source.
In terms of manufacturing processes, automatic winding equipment is used for the windings, with strict control over winding dimensions and conductor arrangement. The double vacuum casting process can effectively remove air bubbles and moisture from the coils, greatly improving the insulation strength of the transformer. During assembly, the coils and core are fitted tightly, the silicon steel laminations are stacked evenly, and strict operating standards are applied to the connections of leads, bushings, and switches.
During final inspection, every CHBEB product undergoes rigorous quality testing. Key tests such as no-load and load tests, partial discharge tests, and lightning impulse tests are strictly controlled.
With the widespread application of dry-type transformers, their manufacturing technology has also made significant progress. It can be expected that dry-type transformers will continue to develop further in the future. It can be predicted that distribution transformers in the 21st century will increasingly favor resin-insulated dry-type transformers with superior performance, low noise, and energy-saving characteristics.
CHBEB GROUP has been deeply engaged in the transformer industry for more than 60 years. With ISO management system certifications, CE/GOST and other international certifications, we have established a solid foundation for compliance. Our status as a National High-Tech Enterprise, together with 5 invention patents and more than 120 patents, demonstrates our technical strength. Through strict manufacturing processes such as automatic winding and double vacuum casting, as well as full-process quality control, we ensure that every product can withstand the test of time and operating conditions.
From our Beijing R&D center to our three production bases in Nanjing and Yueqing, we have provided stable and reliable products and solutions for State Grid and customers in the global power, metallurgy, petrochemical, and other industries.
If you are looking for a trustworthy transformer partner, welcome to contact CHBEB GROUP. Our professional technical team will provide customized selection recommendations and solutions for your project.
There are many reasons for abnormal transformer noise, involving various stages of transportation and installation. If abnormal noise is found during operation, users can check the following aspects:
During operation, the transformer should be regularly monitored and inspected. If any abnormal phenomenon or condition that may affect the normal operation of the transformer is found, the power supply should be disconnected immediately for handling. In serious cases, the manufacturer should be contacted as soon as possible.
In a dry and clean environment, an inspection can generally be carried out once a year or at slightly longer intervals.
In other environments, such as where large amounts of dust or air contaminated by chemical fumes may enter, an inspection should be carried out every three to six months.
During inspection, if excessive dust or foreign objects are found to have accumulated, they must be removed to ensure proper air circulation and prevent insulation breakdown.
A clean cloth can be used to clean the transformer insulators, the raised areas of the lower support blocks, and the outer surfaces of the high-voltage coils. Dry compressed air can be used to blow dust out of the ventilation ducts.
