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Oil-Immersed Transformers Manufacturer & Supplier

Oil-immersed transformer to transformer oil as insulation and cooling medium, divided into single-phase oil-immersed transformer, three-phase oil-immersed transformer two types, the mainstream models cover the D11 oil-immersed transformer, S11-M oil-immersed transformer, S13-M oil-immersed transformer, S15 oil-immersed transformer, more than the use of full-sealed structure, cost-effective, strong and durable, maintenance-free, suitable for outdoor high temperature, wind and sand and other harsh working conditions. JINMA Electrical oil-immersed transformer.

JINMA ELECTRIC oil-immersed transformer factory products voltage covers 10kV-35kV, capacity 10kVA-2500kVA, widely used in outdoor power grids, industrial factories, civil residences, rural photovoltaic and farmland water supply projects.
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What is an Oil-Immersed Transformer

What is an Oil-Immersed Transformer

Oil-immersed transformer to mineral oil, synthetic oil as insulation and cooling medium, relying on electromagnetic induction to achieve AC voltage conversion, and does not change the frequency.

Core Functions

  1. Voltage conversion: realizing power boosting and bucking to meet the needs of long-distance transmission and terminal power consumption;
  2. Heat dissipation and cooling: rely on insulating oil circulation to dissipate heat and maintain long-term stable operation of the equipment;
  3. Safety protection: isolate electrical lines, resist over-voltage impact, and enhance the safety of electricity consumption.

Oil-Immersed Transformers

S22 10KV Oil Immersed Transformer

Rated Capacity: 30-2500kVA
Primary Voltage: 10kv
Secondary Voltage: 0.4kv
Specification: Customized
Certification: GB, CCC, IEC, IEEE, CE
Level 1 Energy Efficiency

S20 10KV Oil Immersed Transformer

Rated Capacity: 30-2500kVA
Primary Voltage: 10kv
Secondary Voltage: 0.4kv
Specification: Customized
Certification: GB, CCC, IEC, IEEE, CE,
Level 2 Energy Efficiency

S18 10KV Oil Immersed Transformer

Rated Capacity: 30-2500kVA
Primary Voltage: 10kv
Secondary Voltage: 0.4kv
Specification: Customized
Certification: GB, CCC, IEC, IEEE, CE
Level 3 Energy Efficiency

SH15 Amorphous Alloy Oil Immersed Transformer

Rated Capacity: 30-2500kVA
Primary Voltage: 6/6.3/10/10.5/11kv
Secondary Voltage: 0.4kv
Specification: Customized
Certification: GB, CCC, IEC, IEEE, CE
Level 1 Energy Efficiency

S13 6-10KV Oil Immersed Transformer

Rated Capacity: 30-2500kVA
Primary Voltage: 6/6.3/10kv
Secondary Voltage: 0.4kv
Specification: Customized
Certification: GB, CCC, IEC, IEEE, CE
Level 3 Energy Efficiency

S11 Series 10kV Oil-Immersed Distribution Transformer

Rated Capacity: 30-2500kVA
Primary Voltage: 10kv
Secondary Voltage: 0.4kv
Specification: Customized
Certification: GB, CCC, IEC, IEEE, CE

35KV Oil Immersed Distribution Transformer

Rated Capacity: 20000-31500kVA
Primary Voltage: 35/37kv
Secondary Voltage: 10.5kv
Specification: Customized
Certification: GB, CCC, IEC, IEEE, CE

110kV Substation Oil-Immersed Transformer

Rated Capacity: 10000-63000kVA
Primary Voltage: 110/115kv
Secondary Voltage: 10.5/11/37kv
Specification: Customized
Certification: GB, CCC, IEC, IEEE, CE

10kV Hermetically Sealed Oil-Immersed Transformer

Rated Capacity: 30-2500kVA
Primary Voltage: 10kv
Secondary Voltage: 0.4kv
Specification: Customized
Certification: GB, CCC, IEC, IEEE, CE
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How an Oil-Immersed
Transformer Works

An oil-immersed transformer operates based on two core principles: electromagnetic induction (energy transfer) and oil circulation cooling (heat dissipation). The detailed working process is as follows:
Primary Winding Activation: When alternating current (AC) flows through the primary winding, it generates a changing magnetic flux in the laminated iron core.
Magnetic Flux Transmission: The iron core concentrates and guides the magnetic flux to the secondary winding, minimizing energy loss.
Voltage Induction: The changing magnetic flux induces an alternating voltage in the secondary winding, with the voltage ratio strictly proportional to the turns ratio (V1/V2 = N1/N2).
Energy Transfer: Electrical energy is transferred from the primary side to the secondary side through the magnetic field, completing voltage conversion.
The insulating oil also serves as an electrical insulator, preventing short circuits between windings and enhancing the transformer's safety performance.
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Oil-Immersed Transformer Structure

Core Advantages of
Our Oil-Immersed Transformers

Our oil-immersed transformers stand out in the global market with superior performance and cost-effectiveness, supported by advanced technology and strict quality control. Below are the core advantages that make us a preferred partner for global clients:

Excellent Heat Dissipation & High Capacity

The insulating oil provides efficient heat transfer, enabling our transformers to handle large capacities (up to 2500kVA) and long-term continuous operation. Cooling systems (ONAN/ONAF/ODAF) are optimized for different capacity ranges, ensuring stable performance even in high-temperature environments.

Low Energy Loss & High Efficiency

We adopt high-quality cold-rolled silicon steel cores (30Q130 grade) and oxygen-free copper windings, combined with optimized winding technology, achieving IE2/IE3 efficiency levels. No-load loss is reduced by 20-30% compared to industry averages, significantly lowering long-term operational costs for power utilities and industrial users.

Strong Weather Resistance & Durability

The hermetically sealed tank design prevents moisture, dust and corrosive substances from entering, ensuring reliable operation in harsh outdoor environments (temperature range: -40℃ to +55℃). The high-quality insulating oil has excellent oxidation resistance and dielectric strength, extending the product lifespan to 25-30 years.

Superior Safety Performance

The insulating oil acts as both a cooling medium and electrical insulator, providing effective insulation between windings and reducing the risk of short circuits. All transformers are equipped with pressure relief valves, oil level indicators and temperature monitors to prevent overpressure, oil leakage and overheating.

Flexible Customization

We support full-custom solutions for voltage level (10kV-220kV), capacity (5kVA-2500kVA), cooling type (ONAN/ONAF/ODAF), and compliance with international standards (IEC, IEEE, ANSI, GB). Our engineering team can design products to meet unique project requirements, such as special voltage ratios and environmental adaptability.

6.Global Compliance & Certification

All products pass IEC 60076, ISO 9001, CE, UL and CB certifications, ensuring compliance with global quality and safety standards. We also provide customized certification documents for specific markets, facilitating customs clearance and project acceptance.

Why Choose Us as Your Oil-Immersed Transformer Partner?

10+ Years of Professional Manufacturing Experience

We have focused on oil-immersed transformer production for over 10 years, with a professional R&D team composed of senior engineers specializing in high-voltage power equipment. Our factory covers 15,000 square meters, equipped with advanced production lines (including automatic winding machines, vacuum oil filling equipment) and strict quality control systems, with an annual production capacity of 5,000 units, enabling us to meet large-scale orders and ensure on-time delivery.

Global Project Experience & One-Stop Service

We have supplied oil-immersed transformers for power grid projects in Africa, industrial facilities in Europe, and infrastructure projects in Southeast Asia. Our one-stop service covers project consultation, customized design, production manufacturing, logistics transportation, on-site installation guidance and after-sales maintenance. Our multilingual team (English, Spanish, Arabic, Russian, French) ensures smooth communication and efficient problem-solving for global clients.

Applications
Use Cases

Distribution transformers are the voltage conversion backbone in all industries using grid electricity. Their voltage rating, thermal class and mounting configuration are designed to suit the application.
01

20 sets of 11kV oil-immersed transformers grid transformation project in Nigeria

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02

Thailand Bangkok 11 sets of KYN28A-24 switchgear + SCB14 dry-type transformer complete project

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03

Grid Upgrade Project for 8 35kV Power Transformers in Kazakhstan

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04

Grid-connected project of 12 PV transformers + ring cabinets in Java, Indonesia

project of 12 PV transformers ring cabinets in Indonesia
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05

15 Units 22kV Oil-immersed Transformer Industrial Park Distribution in Vietnam Project

22kV Oil-immersed Transformer Industrial Park Distribution in Vietnam Project
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OUR PROJECTS

Types Of Oil-Immersed Transformers — Buying Guide

Choosing the right oil-immersed transformer is critical to project performance, cost-effectiveness and safety. This buying guide helps you understand different types and select the most suitable model for your project:

By Cooling Method

（1）Natural Cooling (ONAN)
•Core Features: Natural oil circulation + natural air cooling; no additional cooling equipment; low noise, low maintenance.
•Advantages: Simple structure, reliable operation, low energy consumption; suitable for small to medium capacity.
•Disadvantages: Limited heat dissipation capacity; not suitable for large-capacity or high-temperature environments.
•Capacity Range: 5kVA-500kVA
•Best For: Rural electrification, small substations, residential power supply, small industrial facilities.
（2）Forced Air Cooling (ONAF)
•Core Features: Natural oil circulation + forced air cooling (fans); enhanced heat dissipation capacity.
•Advantages: Higher capacity than ONAN; cost-effective; suitable for medium-capacity projects.
•Disadvantages: Slightly higher noise; requires fan maintenance.
•Capacity Range: 250kVA-1500kVA
•Best For: Industrial parks, medium-sized substations, commercial complexes, regional power grids.
（3）Forced Oil & Air Cooling (ODAF)
•Core Features: Forced oil circulation (pumps) + forced air cooling (fans); maximum heat dissipation capacity.
•Advantages: Suitable for large-capacity, high-load operation; stable performance in high-temperature environments.
•Disadvantages: Complex structure; higher maintenance requirements; higher energy consumption.
•Capacity Range: 1000kVA-2500kVA+
•Best For: Large power grids, key substations, large industrial plants, ultra-high voltage power transmission.
Oil-Immersed Transformer3

By Voltage Level

（1）Low-Medium Voltage (10kV/35kV)
•Core Features: Compact size, easy installation; suitable for distribution networks and medium-voltage transmission.
•Advantages: Cost-effective, wide application range; mature technology, reliable performance.
•Best For: Rural power grids, industrial parks, commercial complexes, small to medium industrial facilities.
（2）High Voltage (110kV/220kV)
•Core Features: High insulation level, large capacity; suitable for long-distance high-voltage transmission.
•Advantages: Efficient power transmission, low line loss; suitable for large-scale power projects.
•Disadvantages: Higher cost; stricter installation and maintenance requirements.
•Best For: Key substations, large power grids, large industrial complexes, power station output.

Configuration Comparison Table

Configuration FeatureNatural Cooling (ONAN)Forced Air Cooling (ONAF)Forced Oil & Air Cooling (ODAF)
Cooling PrincipleOil natural circulation + Air natural coolingOil natural circulation + Air forced coolingOil forced circulation + Air forced cooling
Capacity Range5kVA-500kVA250kVA-1500kVA1000kVA-2500kVA+
Noise Level≤ 55dB≤ 65dB≤ 75dB
Maintenance CostVery LowLowMedium
Energy ConsumptionLowMediumHigh
Applicable EnvironmentNormal temperature (0℃-40℃)Normal-high temperature (0℃-45℃)High temperature (0℃-55℃)
Initial CostLowMediumHigh

Buying Suggestion:
1.Determine capacity and voltage level based on project power demand and power grid conditions;
2.Select cooling method according to ambient temperature and operation load (ONAN for small capacity/normal temperature, ONAF for medium capacity, ODAF for large capacity/high temperature);
3.Consider local standards and certification requirements (e.g., IEC for European markets, IEEE for North American markets);
4.Consult our engineers for free project-specific recommendations, including customized solutions for special scenarios.

Oil-Immersed Transformer Vs. Dry-Type Transformer — Key Differences

Oil-Immersed Transformer Vs. Dry-Type TransformerOil-immersed and dry-type transformers are the two main types of power transformers, with distinct differences in structure, performance, application and cost. Below is a detailed comparison to help you choose the right type:

Oil-Immersed Transformer

Insulation & Cooling Medium:Mineral oil / synthetic oil
Capacity Range:Large (5kVA-2500kVA+)
Voltage Level:Low-high voltage (10kV-220kV+)
Cooling Method:Low-high voltage (10kV-220kV+)
Application Scenario:Outdoor, large-scale power supply (grids, industrial plants, substations)
Fire Safety:General (risk of oil leakage/combustion)
Weather Resistance:Excellent (sealed design, suitable for outdoor)
Maintenance Cost:Low-medium (oil testing, tank inspection)
Initial Cost:Lower (per kVA)
Lifespan:25-30 years

Dry-Type Transformer

Insulation & Cooling Medium:Epoxy resin / air
Capacity Range:Small-medium (0.5kVA-1500kVA)
Voltage Level:Low-medium voltage (0.4kV-35kV)
Cooling Method:AN/AF (air cooling)
Application Scenario:Indoor, small-medium power supply (buildings, data centers, indoor substations)
Fire Safety:Excellent (non-combustible)
Weather Resistance:Poor (not suitable for outdoor)
Maintenance Cost:Very Low (no oil maintenance)
Initial Cost:Higher (per kVA)
Lifespan:20-25 years

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E-mail: sales@jinmatransformer.com

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