Three-dimensional wound core Three-phase Oil-immersed Distribution transformer up to 11kV

Structural Features

Triangular Wound Core: The core is continuously wound from high-quality cold-rolled grain-oriented silicon steel strips using specialized winding machines to form a nearly circular column. Post-winding vacuum annealing eliminates processing stress, reorients the crystal lattice, significantly improves permeability, and optimizes electromagnetic performance.

Fully Sealed Corrugated Tank: Features a triangular corrugated tank design that eliminates the traditional conservator (oil pillow). The elastic deformation of the corrugated fins automatically compensates for volume changes caused by temperature fluctuations, completely isolating the insulating oil from atmospheric moisture and oxygen, enabling maintenance-free operation.

Short-Circuit Resistant Core & Coil Assembly: The transformer assembly forms a robust three-dimensional prism shape. High and low-voltage coils are wound directly onto the core column paper tubes and consolidated with tension rods, upper/lower yoke insulation, and laminated wood blocks to form a solid unity, effectively resisting axial and radial mechanical stresses during sudden short circuits.

Premium Winding Materials: Windings typically utilize low-oxygen copper materials, such as paper-covered flat copper wire or polyvinyl acetal enamelled round copper wire. The HV coil is usually multi-layer cylindrical, while the LV coil adopts a double-layer cylindrical or foil structure to ensure excellent conductivity and mechanical strength.

Key Performance Advantages

1. Ultimate Energy Efficiency (Ultra-Low Loss): Thanks to the optimized magnetic circuit structure, both no-load and load losses are drastically reduced. Compared to conventional products, For example,the S13-M.RL series reduces average no-load loss by approximately 50% and load loss by about 30%.
2. Ultra-Low No-Load Current: Utilizing premium materials and seamless winding technology, the no-load current is significantly suppressed, decreasing by over 75% compared to traditional transformers, greatly enhancing power quality.
3. Silent & Eco-Friendly: The triangular core structure eliminates joint noise found in laminated cores, and the magnetostriction effect is minimized. Operational noise is reduced by approximately 7-9 dB compared to conventional transformers of the same capacity, making it ideal for noise-sensitive areas like residential zones, hospitals, and schools.
4. Superior Power Supply Quality: The perfectly symmetrical three-phase magnetic circuit prevents the generation of the 3rd harmonic, resulting in minimal output waveform distortion and significantly improved power supply reliability and voltage quality.
5. Compact Structure: The nearly circular core columns maximize space utilization, resulting in a compact, solid structure. 

Typical Application Scenarios

Urban & Rural Grid Renovation Projects: Widely used in the upgrading of residential areas and rural power grids as high-efficiency energy-saving distribution equipment.

Noise-Sensitive Areas: Such as upscale residential communities, office buildings, hospitals, schools, and libraries requiring quiet power environments.

Pad-mounted & Prefabricated Substations: Ideal for compact substations due to its small footprint, maintenance-free nature, and high safety profile.

Industrial & Commercial Buildings: Suitable for industrial and commercial distribution systems with large load fluctuations and high demands for power quality, energy conservation, and environmental protection.

Important Notes

The manufacturing process for triangular core transformers is relatively complex, demanding high precision in silicon steel cutting, winding equipment, and vacuum annealing techniques. Consequently, the initial manufacturing cost is typically slightly higher than that of traditional planar laminated core transformers.

Typical Technical Parameters (Reference)

Oil-Immersed Distribution Transformers FAQ

Q: What is the designed service life of an oil-immersed transformer?

Under standardized operation and regular maintenance, high-quality oil-immersed transformers typically have a service life of 30 to 40 years or even longer. In particular, transformers with a fully sealed corrugated tank design completely isolate the internal insulating oil from the outside environment. This effectively delays the aging of insulating materials, significantly extending the equipment’s service cycle.

Q: What daily maintenance do oil-immersed transformers require?

Maintenance requirements vary by structure. For traditional conservator-type (oil pillow type) transformers, it is necessary to regularly check oil levels, conduct oil sample testing (such as breakdown voltage and moisture content tests), and periodically replace the moisture-absorbing silica gel in the breather. For fully sealed transformers, maintenance of the breather and conservator is eliminated. Daily tasks are limited to routine external inspections and cleaning, making them truly “maintenance-free” or “low-maintenance” products.

Q: Are there more environmentally friendly alternatives to mineral insulating oil?

Yes. In addition to traditional mineral oil, we offer eco-friendly transformers that use biodegradable natural esters or synthetic esters as the insulating medium. These ester-based liquids are not only non-toxic and biodegradable but also feature a higher flash point (excellent fire safety performance). They are highly suitable for locations with strict environmental and fire safety requirements (such as indoor substations, areas near forests, etc.).

Q: What is the core difference between sealed and conservator-type transformers?

The core difference lies in whether the transformer is exposed to the atmosphere. Conservator-type transformers are equipped with an independent oil conservator and breather. The oil expands and contracts with temperature changes and absorbs air, requiring more maintenance to prevent moisture absorption and oxidation. Sealed transformers use a fully enclosed structure (such as elastic corrugated tanks), where oil volume changes are accommodated by the deformation of the tank walls. This completely isolates moisture and oxygen from the air, significantly reducing maintenance costs and improving operational reliability.

Q: What are the differences between various vector groups?

If your transformer is supplying power independently to a factory or a residential area and does not need to operate in parallel with other transformers, different vector groups (such as the common Dyn11 and Yyn0) can both be used, though they differ significantly in actual performance. However, if you are expanding capacity or replacing an old unit and the new transformer needs to operate in parallel with the old one, you must strictly check the nameplate of the old transformer. The vector group of the new transformer must be exactly the same as the old one — never rely solely on capacity and voltage ratings!

Q: What should be considered in transformer selection for special environments?

High pollution or coastal salt mist environments: Oil-immersed transformers inherently possess strong environmental adaptability. For coastal or heavy industrial areas, we can provide superior protection against salt mist and corrosion by using special processes such as thickened anti-corrosion coatings and stainless steel accessories, ensuring stable long-term operation even in harsh environments.

High-temperature environments: Sustained high temperatures reduce the transformer’s heat dissipation efficiency and accelerate the aging of insulating oil and paper. Therefore, when operating in high-temperature regions, we usually recommend appropriately reducing the load rate (derating) or installing additional forced air cooling devices.

Low-temperature environments: Extreme cold can cause the viscosity of the insulating oil to increase sharply, severely hindering internal oil circulation and heat dissipation, and potentially making rubber seals brittle, leading to leaks. For such environments, we use special transformer oils with extremely low pour points (such as -45°C or -50°C grades).

High-altitude environments: The thin air and low atmospheric pressure at high altitudes present a dual challenge: first, the reduced convective heat dissipation capability of the air leads to increased transformer temperature rise; second, the reduced insulation strength (breakdown voltage) of the air makes external insulation flashover highly likely. Therefore, transformers used at high altitudes must have increased external insulation distances (such as increased creepage distance on bushings) according to standards, and usually require increased heat dissipation area or derating to compensate for the reduced cooling efficiency.

High-humidity environments: Excessive humidity can easily lead to condensation on the transformer surface, reducing external insulation performance and even causing flashovers. To address this, we enhance the creepage distance design of external insulation components like bushings and ensure the absolute reliability of the sealing system to prevent moisture intrusion.

Dusty/Sandy environments: Dust and sand can easily clog the gaps in cooling fins or corrugated tanks, affecting heat dissipation, and conductive dust may cause external short circuits. For such environments, we optimize the heat dissipation structure design (e.g., increasing fin spacing) and adopt fully sealed protection to prevent dust intrusion.

Q: What information is needed to get a quote for a distribution transformer?

To receive a quick and accurate quotation, please first provide the following core parameters:

• Transformer Type: Oil-immersed / Dry-type
• Rated Capacity (kVA)
• Primary and Secondary Voltage Ratings (e.g., 33kV / 0.4kV)
• Rated Frequency (50Hz or 60Hz)
• Number of Phases (Single-phase or Three-phase)
• Winding Material: Supports copper or aluminum windings, each with its own cost and performance advantages.
• Vector Group & impedance voltage (%): (Must be provided if parallel operation with multiple units is required)

Additionally, our transformers support customization. You can supplement the following information based on your actual needs:

• Tap Changer Type (Standard off-circuit tap changer, or optional on-load tap changer)
• Loss Standards: Are there specific loss standards or energy efficiency class requirements?
• Installation environment (indoor/outdoor, altitude, extreme temperature, etc.)
• Other Requirements (e.g., applicable standards, special protection ratings, instrument accessories, etc.)

If you are looking for reliable power support for your project, please contact the Kima Electric team.

• Direct Factory & Manufacturer: We are a professional China Three-dimensional wound core Three-phase oil-immersed distribution transformer manufacturer (available in 6.3kV,10kV,11kV, and other voltages). Our factory is equipped with advanced production facilities and accepts OEM/ODM orders.
• Reliable Supplier: We serve as a trusted international supplier for global buyers looking to source high-efficiency and low-loss Three-dimensional wound core Three-phase oil-immersed distribution transformers from China.
• International Standards & Global Reach: Our transformers are rigorously tested to comply with IEC 60076 and other international standards. We export to diverse markets across Southeast Asia, Africa, and the Middle East, adapting to various local grid environments.
• Competitive Quotation: Contact us today to discuss your project requirements, get a customized solution, and receive a free wholesale quote.

◆ Convenient Inquiry Process

You can contact us via our website, email, and other channels, or download and fill out the “Inquiry Application Form” on our official website.

You can also directly provide your existing technical documents, drawings, etc., as a basis for requirement evaluation. We will provide you with a quotation as soon as possible.

◆ Production and Quality Control

Before formal production, we will provide a detailed technical proposal, including specifications and structural drawings, for your review and confirmation.

We strictly implement the ISO quality management system, comprehensively monitoring every link including raw materials, production processes, and finished product inspection, ensuring that every customized product possesses stable and reliable quality.

◆ Delivery and After-Sales Service

We use dedicated wooden crates that meet international standards for packaging, lined with high-performance moisture-proof materials, to ensure the equipment remains absolutely safe and dry during long-distance transportation.

Detailed user manuals, maintenance manuals, and related documents are provided with the shipment.

Remote or on-site installation guidance and commissioning services can be provided upon request.

We provide comprehensive after-sales support, including technical consultation, troubleshooting, and spare parts supply, ensuring the long-term stable operation of the product.