From Silicon Steel to Iron Core: Full Analysis of Lamination and Annealing Process for 2000kVA Oil-Immersed Transformer Cores
When it comes to manufacturing high-efficiency 2000kVA oil-immersed transformer cores, the combination of premium silicon steel, precise lamination, and a tightly controlled annealing process defines the final performance.
GNEE, as a specialized transformer core factory with over 18 years of experience, delivers complete lamination and annealing solutions directly from our 30,000 m² production base in Anyang, China.
In this article, we provide a full analysis of how our lamination and annealing process for 2000kVA oil-immersed transformer cores guarantees superior magnetic properties and energy efficiency - and why choosing the manufacturer directly impacts your transformer's reliability.
Click to learn more about GNEE grain-oriented silicon steel
GNEE factory workshop with rows of grain-oriented silicon steel coils
1. Why Silicon Steel Selection Is Critical for 2000kVA Oil-Immersed Transformer Cores
Grain-Oriented vs. Non-Oriented Steel for 2000kVA Oil Cores
The core of a 2000kVA oil-immersed transformer must channel magnetic flux with minimal resistance. Only cold-rolled grain-oriented (CRGO) silicon steel can deliver the required anisotropic magnetic properties. Unlike non-oriented steel, CRGO silicon steel has a specifically engineered crystal structure that greatly reduces core losses in the rolling direction. For a 2000kVA oil-immersed transformer core, even a 0.1 W/kg difference in specific core loss translates into thousands of kilowatt-hours saved annually. GNEE exclusively sources prime CRGO silicon steel from certified mills such as Baosteel and Nippon Steel.
Common CRGO Grades Used in 2000kVA Transformer Cores
We select grades according to loss requirements and international standards. Typical materials for 2000kVA oil-immersed cores include 27QGH100, 27QG100, or 23QGH080, with thicknesses of 0.23 mm or 0.27 mm. Lower thickness and higher silicon content reduce eddy current loss, but they also demand more careful handling during lamination. Our engineering team recommends the optimal grade after evaluating your target no-load loss class (e.g., S11, S13, or even S15 equivalent). Need material advice? Contact GNEE for a free core design proposal.
2. Step-by-Step Lamination Process of 2000kVA Oil-Immersed Transformer Cores
The physical assembly of the lamination stack defines the mechanical integrity and magnetic continuity of the core. GNEE's lamination process for 2000kVA oil-immersed transformer cores combines automated precision with in-process inspection.
Slitting and Cross-Cutting for Precise Lamination Dimensions
CRGO coils first pass through high-accuracy slitting lines that cut strip widths to the exact core leg and yoke dimensions. Subsequently, automatic cross-cutting lines shear laminations to length with a tolerance of ±0.2 mm. For a 2000kVA oil-immersed transformer core, consistent lamination geometry is non-negotiable; any mismatch creates air gaps that raise magnetizing current.
Burr Control and Surface Insulation Preservation
Slitting and cutting inevitably generate mechanical stress and micro-burrs. Our process keeps burr height below 0.02 mm through optimized blade clearance and regular tool maintenance. Excessive burrs not only risk short-circuiting interlaminar insulation but also disturb the magnetic path. Each lamination retains its factory-applied C5 or C6 insulation coating, which withstands the annealing temperature and provides long-term interlayer resistance.
Core Stacking Configuration: Step-Lap Joint Design
The 2000kVA oil-immersed transformer core requires a multi-step lap (usually 5- or 7-step) joint to smooth flux transfer at the corners. Our skilled technicians assemble laminations alternately in a precisely angled pattern, significantly lowering no-load loss and noise compared with simple butt-lap designs. The table height and stacking pressure are monitored to maintain a stacking factor ≥ 97%.
Technician stacking silicon steel laminations
3. The Annealing Process: Restoring Magnetic Properties in 2000kVA Oil-Immersed Transformer Cores
Even the cleanest cutting introduces plastic deformation and residual stress at the lamination edges, which pin magnetic domain walls and raise core loss. Annealing is the only way to relieve these stresses, and GNEE applies a meticulously controlled batch annealing process for every 2000kVA oil-immersed transformer core.
Why Annealing Is Necessary After Lamination Cutting
Stresses from punching and shearing can increase specific core loss by up to 20%. For a 2000kVA unit, this level of increase reduces efficiency class and causes excess heating. Our annealing process for 2000kVA oil-immersed transformer cores restores nearly the original magnetic permeability and guarantees that your core meets guaranteed loss values.
Batch Annealing Furnace Parameters: Temperature and Atmosphere
We load the stacked and clamped core into a bell-type electrically heated furnace. The core is heated to approximately 780–810 °C in a protective pure nitrogen atmosphere (oxygen content < 5 ppm). The temperature is held for 4 to 6 hours, depending on core mass, and then the furnace undergoes a controlled slow cooling phase. Rapid cooling or oxygen ingress would oxidize the steel surface and damage insulation - our automated atmosphere system completely eliminates this risk.
Effect of Annealing on Core Loss and Magnetizing Current
Post-annealing, the 2000kVA oil-immersed transformer core exhibits a typical loss reduction of 8–15% and a marked improvement in permeability at 1.7 T. GNEE measures every annealed core using a computerized AC magnetic test bench; test reports accompany each shipment as proof of performance. Request a sample test certificate with your inquiry.
4. Quality Assurance and Testing for 2000kVA Oil-Immersed Transformer Cores
To deliver cores that perform identically to their design calculations, we embed multiple quality gates throughout production.
Core Loss and Magnetizing Current Measurement
Every completed 2000kVA core is placed on a calibrated test station that measures no-load loss and magnetizing current at rated flux density and frequency (usually 50/60 Hz). Our measurement uncertainty is less than ±1.5%, traceable to IEC 60076-1. These measured values are stamped on the core rating plate.
Dimensional and Visual Inspection
After lamination and annealing, the core undergoes a full dimensional check: leg centre distances, window height, limb flatness, and yoke alignment. Surface insulation resistance is spot-checked with a 500 V DC megger. Any core that does not meet our internal acceptance criteria is rejected before packaging.
Standards and Certifications
GNEE operates under an ISO 9001:2015 quality management system. Our 2000kVA oil-immersed transformer cores comply with IEC 60076, GB/T 6451, and can be adapted to specific utility standards (DOE, NEMA, etc.). Certification documents are available upon request, reinforcing our position as a trusted manufacturer.
5. Technical Specifications of GNEE's 2000kVA Oil-Immersed Transformer Cores
The following table summarizes typical parameters for a standard 2000kVA oil-immersed transformer core. All values can be fully customized to your electrical design.
| Parameter | Typical Specification / Range |
|---|---|
| Rated Power Capacity | 2000 kVA |
| Primary High Voltage | 10 kV / 11 kV / 13.8 kV / Custom |
| Secondary Low Voltage | 0.4 kV / 0.69 kV / Custom |
| Core Material | Grain-Oriented Silicon Steel (CRGO) |
| Preferred CRGO Grades | 27QGH100, 27QG100, 23QGH080 |
| Lamination Thickness | 0.23 mm or 0.27 mm |
| Stacking Factor | ≥ 97% |
| Core Configuration | 3-limb / 5-limb (according to flux density) |
| Joint Type | Step-lap (5-step or 7-step) |
| Annealing Atmosphere | Pure nitrogen (< 5 ppm O₂) |
| Annealing Temperature | ~800 °C |
| No-Load Loss (Reference, at 1.7 T 50 Hz) | ≤ 1750 W (grade dependent) |
| Core Weight (Approx.) | 700 – 950 kg |
| Applicable Standards | IEC 60076, GB/T 6451, ISO 9001 |
| Packaging | Fumigated wooden case with moisture barrier |
Conclusion
From silicon steel strip to a fully annealed, tested iron core, the lamination and annealing process directly determines the efficiency and longevity of a 2000kVA oil-immersed transformer core.
GNEE couples tried-and-true manufacturing discipline with modern automation, ensuring that every core we ship delivers low loss, low noise, and field reliability. When your next project demands a high-performance 2000kVA oil-immersed transformer core built to your exact parameters, let GNEE be your long-term partner.
Speak with our engineers, get a competitive quote, and confirm your delivery schedule - submit your inquiry today and feel the factory advantage.
How much power can a 2000 kVA transformer supply?
The actual usable power depends on the power factor of the electrical system. At a standard 0.8 power factor, the real output power is:
P=2000×0.8=1600 kWP=2000\times0.8=1600\text{ kW}P=2000×0.8=1600 kW
Therefore, a 2000 kVA transformer can typically provide about 1600 kW of usable power.
What is the difference between a 2000 kVA oil immersed transformer and a dry type transformer?
A 2000 kVA oil immersed transformer uses insulating oil for cooling and electrical insulation, making it suitable for outdoor substations, industrial plants, and heavy-load applications. A dry type transformer uses air or cast resin insulation instead of oil, which makes it safer for indoor environments such as hospitals, shopping malls, office buildings, and data centers where fire protection is important.
How much does a 2000 kVA transformer weigh?
The total weight varies depending on the transformer design, voltage rating, cooling method, and winding material. Generally, a 2000 kVA oil immersed transformer weighs between 3500 kg and 6500 kg, while a dry type transformer usually weighs between 2500 kg and 5000 kg.
How much insulating oil is used in a 2000 kVA oil filled transformer?
A standard 2000 kVA oil immersed transformer typically contains around 1200 to 2500 liters of transformer oil. The exact oil quantity depends on radiator configuration, cooling design, voltage class, and manufacturer specifications.
What voltages are commonly available for a 2000 kVA transformer?
The most common primary voltages are 11kV, 13.8kV, 15kV, 20kV, 22kV, and 33kV, while common secondary voltages include 400V, 415V, 440V, 480V, and 690V. Customized voltage combinations can also be produced according to project requirements.
Which is better, an oil type or dry type transformer?
Oil immersed transformers are generally preferred for outdoor installations and high-capacity industrial applications because they offer better cooling efficiency, stronger overload capability, and longer service life. Dry type transformers are usually selected for indoor use because they provide better fire safety, lower environmental risk, and simpler maintenance.