3D Wound Core Oil-immersed Transformer

The Three-Dimensional (3D) Wound Core Oil-immersed Transformer represents a significant evolution in distribution transformer technology. By replacing the traditional planar, stacked-lamination structure with three identical, symmetrically arranged rectangular core frames, it forms a closed equilateral triangle. This innovation aligns with the grain orientation of electrical steel or amorphous metal strips, facilitating a highly efficient magnetic circuit.

Performance Advantages

Data-backed research confirms that 3D wound core transformers significantly outperform conventional designs in several key metrics:

Superior Energy Efficiency: The absence of air gaps at joints and the elimination of the "corner" losses found in traditional stacked cores allow for substantial efficiency gains. Studies indicate that 3D wound core designs can achieve up to 60% lower no-load losses compared to traditional silicon steel transformers.
Enhanced Operational Stability: The three-phase magnetic circuit is perfectly symmetrical, with identical path lengths for each phase. This balance reduces reactive current and ensures uniform voltage regulation. Furthermore, the robust, tightly wound structure provides superior mechanical strength, offering enhanced resistance to the electromagnetic forces experienced during short-circuit events.
Significant Noise Reduction: Traditional cores are prone to vibration at joints, which is a primary source of acoustic noise. The 3D wound core’s seamless, compact construction effectively suppresses these vibrations, typically resulting in noise levels 7 to 10 decibels lower than equivalent stacked-core units.
Material and Space Optimization: The structural integrity and symmetry allow for a more compact footprint. Manufacturers often realize a 10–15% reduction in production costs and approximately 20% less silicon steel material usage compared to traditional counterparts of the same capacity, contributing to a lower total cost of ownership over the equipment's lifespan.

Industry Applications

Given these technical benefits, 3D wound core oil-immersed transformers have become the preferred choice for modernizing electrical infrastructure. They are widely deployed in urban distribution networks, data centers, renewable energy projects (such as wind and solar farms), and high-density industrial parks. From 10kV distribution to higher capacity 110kV substations, this technology is central to global initiatives aimed at grid decarbonization, noise pollution mitigation, and maximizing the economic efficiency of power delivery systems.

As regulatory mandates for energy efficiency tighten, the 3D wound core transformer stands as a reliable, high-performance solution for the next generation of smart and sustainable power grids.

Quality Assurance & Core Process：

1. High-Permeability Grain-Oriented Electrical Steel

We utilize Hi-B high-permeability grain-oriented (HPGO) electrical steel—the same grade specified by TBEA and CHINT—as the transformer core material, with standard nominal thicknesses of 0.23 mm and 0.27 mm. Core laminations are manufactured using high-precision cutting equipment to guarantee a burr height of ≤0.02 mm. The assembly incorporates a precision step-lap lamination structure, maintaining optimal clamping pressure without imparting excessive mechanical stress to the electrical steel, combining high-B steel characteristics with an optimized magnetic flux density.

2. High-Conductivity Winding Conductors & Core-Coil Assembly

High-conductivity electrolytic copper or aluminum conductors are selected based on transformer capacity, voltage class, and loss requirements. Incoming materials undergo stringent quality inspections for dimensions, electrical resistance, surface quality, and traceability. During the winding process, conductor tension, winding height, layer insulation, and conductor positioning are precisely controlled to ensure resistance consistency and mechanical stability, thereby minimizing load losses and temperature rise during operation.

During core-coil active part assembly, coil height, axial clamping force, radial support, and spacer block positioning are precisely controlled. Proper mechanical clamping prevents coil displacement during transport, normal operation, and short-circuit conditions. Meanwhile, clamping forces are strictly regulated to avoid excessive stress on conductors and insulation materials. Our mechanical design accounts for both radial and axial electromagnetic forces, safeguarding short-circuit withstand capability and long-term dimensional stability.

3. Advanced Insulation System (Oil-Immersed & Dry-Type)

For oil-immersed transformers, we utilize high-grade insulation materials, including Kraft paper, thermally upgraded paper, pressboard, and transformer-grade laminated board. For dry-type transformers, we employ DMD, NMN, Nomex, fiberglass, and epoxy resin systems. Insulation thickness, overlap width, oil duct dimensions, electrical clearances, and mechanical positioning are strictly regulated. All insulation materials are stored under climate-controlled conditions to minimize moisture absorption and contamination, ensuring stable dielectric strength and long-term insulation reliability.

4. Controlled Vacuum Drying

We apply a controlled drying curve regulated by temperature, vacuum level, and duration parameters, rather than relying on fixed cycle times. The process comprises controlled pre-heating, evacuation, primary drying, and final soak phases, with continuous temperature and vacuum monitoring and logging. End-point determination is based on validated process criteria and moisture limits. This process minimizes residual moisture in cellulose insulation, maximizing dielectric strength, retarding insulation aging, and extending overall service life.

5. Vacuum Epoxy Resin Casting

For cast-resin dry-type transformers, we utilize controlled vacuum casting technology. Resin-to-hardener ratio, material temperature, vacuum level, mixing time, pouring conditions, and curing temperatures are strictly regulated. Vacuum degassing minimizes micro-voids prior to pouring, while controlled curing ensures stable mechanical and thermal properties. Finished coils undergo thorough visual and electrical inspections, including routine partial discharge (PD) testing. This process eliminates internal voids, ensuring reliable insulation performance throughout the transformer's service life.

6. Clean Assembly & Torque Control

Final assembly takes place in a controlled environment to minimize contamination from dust, metallic particles, and foreign objects. Critical components are inspected for cleanliness, dimensional accuracy, and insulation condition. Electrical clearances, lead routing, grounding connections, and mechanical supports are rigorously controlled throughout assembly. Critical bolted joints are tightened to specified torque values using calibrated equipment and fully logged. Prior to sealing the tank or enclosure, a thorough internal inspection ensures no tools, loose parts, or foreign material remain.

7. 100% Factory Routine Testing

Every transformer undergoes 100% routine testing prior to dispatch, complying with applicable IEC standards, approved technical specifications, and customer requirements. Standard test routines include winding DC resistance, voltage ratio, vector group verification, no-load loss and current, load loss and short-circuit impedance, applied voltage withstand, and induced overvoltage withstand tests. Special tests—such as partial discharge (PD), dissipation factor (tan δ), or sweep frequency response analysis (SFRA)—are conducted upon request. Each unit is assigned a unique serial number linked to its material records, manufacturing data, and final test reports, ensuring end-to-end traceability.