Oil Immersed Transformer
Our oil-immersed transformers are fully customizable, spanning capacities from 30 kVA to 31,500 kVA at voltages up to 38.5 kV. Whether your application calls for standard distribution, amorphous alloy, 3D triangular wound core, or intelligent on-load tap-changing models, each unit is engineered to meet the precise demands of your grid.
Built with vacuum oil-filling technology and fully sealed corrugated tanks, every transformer delivers efficient heat dissipation and strong short-circuit resistance. Advanced core materials reduce no-load losses by up to 75%, extending reliable performance across the full service life.
Custom Transformer Solutions
Voltage: 6-38.5 kV
Capacity: 30-31,500 kVA
Frequency: 50/60 Hz
Access Top Quality Transformer Solutions to Elevate Your Power Projects
Reliable Oil Immersed Transformer For Sale
S13(20, 22)-M Series Energy-Efficient Oil Immersed Distribution Transformer
Standard 10kV distribution transformers using high-permeability grain-oriented silicon steel with a fully sealed corrugated tank structure. For units with a capacity of 800 kVA and above, we provide an optional gas relay for real-time internal fault detection and system protection.
Voltage: 6-11 kV
Capacity: 30 kVA – 2,500 kVA
Vacuum oil-filling process
Fully sealed maintenance-free
Optional gas relay(≥800kVA)
S13(20,22)-M.RL Series Three-Dimensional Triangular Wound Core Transformer
A specialized series featuring a 3D triangular core structure that eliminates traditional magnetic circuit joints. This symmetrical design achieves a 10-15 decibel noise reduction and minimizes stray magnetic fields, making it ideal for noise-sensitive residential environments.
Voltage: 6-11 kV
Capacity: 30 kVA – 2,500 kVA
Ultra-quiet operation
No-joint magnetic circuit
Fully symmetrical structure
S(B)H15(21, 25)-M Series Amorphous Alloy Oil Immersed Transformer
High-performance units utilizing 0.025 mm amorphous alloy ribbons to slash no-load losses by 75% compared to S11 models. Combined with low-voltage copper foil windings, this series offers superior short-circuit resistance and the highest energy efficiency for utility grids.
Voltage: 6-11 kV
Capacity: 30 kVA – 2,500 kVA
75% no-load loss reduction
Amorphous alloy ribbon core
Copper foil winding technology
SZ18 On-Load Tap-Changing Energy-Saving Power Transformer
Designed for 35kV sub-transmission networks, these heavy-duty transformers feature integrated on-load tap changers (OLTC). They maintain a stable secondary voltage by automatically adjusting the tap position during load fluctuations in industrial and rural grids.
Voltage: 35 kV – 38.5 kV
Capacity: 3,150 kVA – 31,500 kVA
On-load voltage regulation
Remote monitoring capabilities
Heavy-duty substation design
SZ13-M·ZT Intelligent On-Load Tap-Changing Transformer
An intelligent solution that automatically adjusts its capacity rating to match real-time power demand. It effectively solves “over-sizing” issues in areas with significant seasonal or diurnal load variations, drastically reducing operational losses during off-peak periods.
Voltage: 6-11 kV
Capacity: 30 kVA – 630 kVA
Automatic capacity regulation
Smart grid terminal integration
Energy loss optimization
YB-D Series Underground Compact Substation
A modular underground substation consisting of a buried transformer unit and a surface-level LED advertising lightbox. The enclosure features a fully welded, submersible design with an automatic drainage system to ensure safe operation during extreme flooding events.
Voltage: 6-11 kV
Capacity: 30 kVA – 1,600 kVA
Submersible waterproof structure
Integrated media lightbox
Minimal surface footprint
10 kV S13(20, 22)-M.RL Series Sample Specifications — Full Data for All Series Available Upon Request
Specifications
| Capacity (kVA) | High Voltage (kV) | High Voltage Tap Range (%) | Low Voltage (kV) | Frequency (Hz) | Connection Group Number | No-load Loss (W) | Load Loss (W) | No-load Current (%) | Short-circuit Impedance (%) | ||||
| S13 | S20 | S22 | S13 | S20 | S22 | ||||||||
| 30 | 6 6.3 6.6 10 10.5 11 | ±5 ±2 × 2.5 | 0.4 | 50 | Dyn11 Yyn0 | 80 | 70 | 65 | 630/600 | 505/480 | 455/430 | 0.3 | 4 |
| 50 | 100 | 90 | 80 | 910/870 | 730/695 | 655/625 | 0.25 | 4 | |||||
| 80 | 130 | 115 | 105 | 1310/1250 | 1050/1000 | 945/900 | 0.22 | 4 | |||||
| 100 | 150 | 135 | 120 | 1580/1500 | 1265/1200 | 1140/1080 | 0.21 | 4 | |||||
| 160 | 200 | 180 | 160 | 2310/2200 | 1850/1760 | 1665/1585 | 0.19 | 4 | |||||
| 200 | 240 | 215 | 190 | 2730/2600 | 2185/2080 | 1970/1870 | 0.18 | 4 | |||||
| 250 | 290 | 260 | 230 | 3200(3050) | 2560/2440 | 2300/2195 | 0.17 | 4 | |||||
| 315 | 340 | 305 | 270 | 3830/3650 | 3065/2920 | 2760/2630 | 0.16 | 4 | |||||
| 400 | 410 | 370 | 330 | 4520/4300 | 3615/3440 | 3250/3095 | 0.16 | 4 | |||||
| 500 | 480 | 430 | 385 | 5410/5150 | 4330/4120 | 3900/3710 | 0.15 | 4 | |||||
| 630 | 570 | 510 | 460 | 6200 | 4960 | 4460 | 0.15 | 4 | |||||
| 800 | 700 | 630 | 560 | 7500 | 6000 | 5400 | 0.14 | 4.5 | |||||
| 1000 | 830 | 745 | 665 | 10300 | 8240 | 7415 | 0.13 | 4.5 | |||||
| 1250 | 970 | 870 | 780 | 12000 | 9600 | 8640 | 0.12 | 4.5 | |||||
| 1600 | 1170 | 1050 | 940 | 14500 | 11600 | 10440 | 0.11 | 5 | |||||
| 2000 | 1360 | 1225 | 1085 | 18300 | 14640 | 13180 | 0.1 | 5 | |||||
| 2500 | 1600 | 1440 | 1280 | 21200 | 14840 | 13360 | 0.1 | 5 | |||||
Discover Core Advantages of Transformers to Optimize Your Power Layout
Remarkable Advantages of Unicore Oil Immersed Transformers
High Efficiency and Low-Loss Performance
The core utilizes grain-oriented silicon steel or amorphous alloy ribbons to minimize magnetic resistance. Our S22 and Amorphous Alloy series reduce no-load losses by up to 75% and no-load current by 80%. These units meet the latest global energy-efficiency standards, significantly lowering long-term operational costs for utility grids and industrial plants.
Hermetically Sealed and Leak-Free
We employ fully sealed corrugated tank structures and vacuum oil-filling technology to eliminate air and moisture from the windings. This design prevents oil oxidation and aging, ensuring zero oil leakage during the equipment’s lifecycle. The hermetic seal provides maintenance-free performance while preserving superior dielectric strength.
Superior Heat Dissipation and Overload
Oil-immersed cooling provides higher thermal conductivity compared to dry-type insulation. The corrugated tank design maximizes surface area for natural heat dissipation, while forced air cooling (ONAF) is available for high-capacity units. This ensures stable operation under sustained load and superior short-circuit withstand capability in harsh environments.
Marine-Grade Anti-Corrosion Protection
The enclosures undergo rigorous acid washing, phosphating, and three-layer paint processes, including marine-grade anti-corrosion coatings. For specialized environments, 304 stainless steel tanks are available. This provides exceptional resistance to salt spray, moisture, and UV radiation, making them ideal for coastal, underground, and industrial areas.
Comprehensive Safety and Fault Protection
Units are equipped with advanced protection components, including pressure relief valves and multi-functional oil temperature indicators. For units above 800 kVA, gas relays (Buchholz) are standard to provide real-time fault alerting and automatic tripping. These multi-layered safety mechanisms prevent tank rupture and protect the entire power system.
Smart Monitoring and Remote Control
Integrated intelligent temperature controllers and GPRS-enabled load monitoring terminals support real-time data acquisition. Users can remotely track temperature, load levels, and power factor via integrated distribution management systems. This digital integration simplifies grid management and reduces on-site inspection requirements and costs.
30+
Years in the Sector
Offering top-quality transformers and services worldwide since 1993.
18+
International Awards
Unicore has received multiple awards, recongition and certificates globally.
2.4k
Helping Projects Thrive
Supporting 2,400+ power projects across industries worldwide.
80+
Global Marketing
Serving clients and partners across 80+ countries and regions.
Trusted by Clients Across Industries and Continents
Unicore Oil Immersed Transformer Global Cases
Oil Immersed Transformer to Malaysia
Urban Infrastructure– Power Grid
800 kVA
Oil Immersed Transformer to Gambia
Municipal Substation– Public Utility
2,500 kVA
Oil Immersed Transformer to Ecuador
Industrial Park– Power Distribution
1,250 kVA
UNICORE ELECTRIC
Transformer Solutions
Collaborating with Industry Leaders to Deliver Excellence in Power Solutions
Our Global Partners Network
Real Experiences from Transformer Professionals Who Trust Unicore
What Our Clients Say
High Reliability, S13 Series Distribution Transformer
“We sourced the S13-M series for a grid upgrade project in a remote mining area. The build quality of the vacuum-filled, hermetically sealed tanks is impressive, providing excellent protection against harsh outdoor dust and moisture. For our larger 1250 kVA units, the optional gas relay adds a critical layer of safety that our engineers highly value. A very solid, dependable product.”
Robert
Australia
⭐⭐⭐⭐⭐
Exceptional Quietness, S13-M.RL 3D Wound Core Series
“For our latest residential development, noise reduction was a non-negotiable requirement. The S13-M.RL three-dimensional wound core units delivered exactly what was promised. The noise level is noticeably lower—at least 10 decibels quieter than the traditional units we previously used. It’s the perfect solution for urban substations where silence and efficiency are priorities.”
Stefan
Germany
⭐⭐⭐⭐⭐
Why Choose Unicore
Your Trusted Partner in Power Solutions
Built for grid, industrial, and infrastructure sectors, our oil immersed transformers combine 75% energy savings with zero-leakage reliability. With 30 years of expertise, we deliver high-ROI power solutions that excel in the world’s harshest environments.
Tailored Engineering Solutions
Custom voltage, capacity, and core materials (Amorphous/3D Wound) designed to match your specific grid requirements and climate.
Proven Operational Stability
100% factory pre-testing and lightning impulse verification ensure long-term stability and high dielectric strength in harsh environments.