1,000+ Electrical Transformers (7.2–34.5 kV, 25–3000 kVA) — UL Evaluated, Certificate of Compliance Available — In Stock & Ready to Ship from Houston, CA & Florida. Contact Us Today!
As a specialized manufacturer of Heavy Duty Transformers, Daelim Transformer understands that these units are not just equipment—they are the backbone of the grid. A heavy-duty transformer is a strategic asset that ensures continuous power delivery and grid stability.
Smart Efficiency to Protect Your Bottom Line We use high-grade CRGO steel cores to significantly reduce energy losses and operational costs. With integrated SCADA and DGA (Dissolved Gas Analysis) monitoring, you get real-time data for predictive maintenance, preventing expensive downtime and lowering your total cost of ownership.
All parameters listed represent standard dimensions and operating conditions of Daelim Transformer’s heavy duty transformer. Custom configurations are available upon request:
Transformer Parameter | Specification / Range |
Capacity range | 100 MVA – 500 MVA |
Voltage range | 110 kV – 345 kV |
Frequency | 50 / 60 Hz |
Cooling method | ONAN, ONAF, OFAF, ODAF, ODWF |
Insulation medium | Mineral oil, ester fluid (FR3), Dry-type option |
Winding material | Copper is standard. Aluminium available on request |
Tap-changer | On- load OLTC, Off-load |
Temperature operation range | −25 °C to +45 °C (arctic and tropic conditions available on request) |
Noise level | Limits per all major global standards. A low noise option is also available. |
Service life | 20-30 years under normal operating conditions |
Applicable standards | IEC – ANSI/IEEE – CSA – AS/NZS |
Maximizes magnetic permeability and significantly reduces losses compared to conventional designs. Reduces operating costs and unit carbon output.
Transformer design minimizes circulating current and switching stress, delivering superior voltage regulation reliability for mission-critical data center power infrastructure
Seismic hardened tank design. Our transformers withstand Zone IV seismic loading - essential for industry and grid infrastructure in regions with frequent earthquakes.
Sensors that measure oil temperature, load current, gases generated in the oil are connected to your distributed control system. This enables predictive maintenance of your heavy duty transformer, significantly reducing total maintenance costs and downtime of your device.
Modular radiator banks with automatic fan control ensure full rated capacity even at high temperatures - eliminating derating and avoiding capacity shortfalls during peak summer hours.
Environment: High-voltage interconnector and transmission substations, HVDC transmission, step-up transformers in power plants.
Pain point: Any failure in the transformer causes an interruption in the supply of electricity to a large number of users. The investor wants a reliable supplier, with a large selection of spare parts and fast delivery times, as well as proper support from the manufacturer engineering team.
Our solution: Transformers up to 500 MVA, with full IEC, ANSI/IEEE, IEEE, CSA, AS/NZS standard documentation, on-site commissioning team and a reliable supply of spare parts and an extensive distributor network.
Environment: Steel plants, aluminum and cement factories, mines, with significant influence of higher harmonics and intermittent load.
Pain Point: Current and voltage harmonic components that affect operational safety and premature aging of insulation. Transformers have a shorter lifespan.
Our Solution: Transformer design with improved cooling, low-impedance windings and harmonic component mitigation. Our transformers are factory tested for the impact of higher harmonics.
Environment: Offshore platforms, oil refineries, LNG terminals, chemical plants.
Pain point: The equipment must operate reliably in aggressive conditions when exposed to various fumes, hazardous substances and chemical products. It is especially demanding to work in areas with a high risk of explosions and fires.
Our solution: Fireproof equipment, with stainless steel, with additional protective features such as gas detection relays and improved cooling. Daelim Transformer’s transformers are supplied with full ATEX and IECEx documentation.
Environment: Mountain hydroelectric power plants, ski centers, desert solar power plants, mining in the arctic circle.
Pain point: Air at higher altitude reduces the dielectric strength of the insulating oil. Extreme weather conditions affect the viscosity of the oil and its ability to cool the transformer.
Our solution: Insulation adapted to extreme weather conditions, according to appropriate standards.
Environment: Large data centers, hospitals and airports.
Pain point: Voltage disturbances can disrupt the operation of UPS systems and cause data loss, which can represent incalculable damage. Extremely high controllability of the transformer voltage is required.
Our solution: Precision wound transformers, with OLTC + AVR. Effectively limits circulating currents and reduces switching stresses during OLTC operation.
Daelim Transformer offers full customization for every type of your project. Large heavy duty transformers require a specialized approach – one that our engineering team applies from the very first stage of production through to final delivery. The customization process includes:
Electrical parameters
Environmental adaptations
Smart grid features
Production and quality control of transformers is at the highest level at Daelim Transformer. The entire process is rigorous and goes through several steps, including specific and factory acceptance testing.
Routine Tests | Type Tests (on request) |
Voltage ratio & vector group | Temperature rise test |
Winding resistance | Lighting impulse test |
No-load losses & current | Short-circuit withstand |
Load loss & impedance | Noise level measurement |
Applied & induced voltage | Partial discharge test |
Oil leakage & tank pressure | Seismic qualification |
Packaging and shipping of heavy duty transformers presents unique challenges due to their large size and the sensitivity of their components. Daelim Transformer is committed to safeguarding your transformer throughout packaging and transport, minimizing the risk of mechanical damage and moisture ingress to ensure it arrives in optimal condition. The key aspects of preparation and transportation include the following:
We remain in your support even after the transformer is delivered. All our units are delivered with an appropriate warranty, which can be extended according to your needs. Our warehouses are well stocked with spare parts, ensuring fast delivery to any location worldwide when needed.
For heavy duty transformers, our team does flexible design – allowing for main parts upgrades and component retrofits as needed, helping extend service life and ensure long term durability.
Support element | What you get |
Warranty period | No less than 24 months |
Extended warranty | Up to 60-month extended warranty available |
Response time | Fast remote support with coordinated on-site service for critical issues |
Spare parts | Full range of critical spare parts is available to support fast maintenance and ensure continuous transformer operation |
Commissioning support | Factory-trained commissioning engineers; energisation check-list and test record template supplied |
In November 2025, our team delivered a 180 MVA 230/34.5/13.8 kV three-winding heavy duty transformer to a renewable energy customer in the USA . It was designed and manufactured according to the IEEE C57.12.00 standard and comes with a two-stage cooling system and OLTC for precise voltage regulation, which is a very important feature for transformers used in renewable energy applications. Qualitrol instrumentation was specified throughout, providing the client with real-time thermal and operational monitoring from the first day of use.
This project demonstrates Daelim Transformer’s capability to produce heavy duty transformers at the upper limits of power and engineering demands. We are able to manufacture the transformer according to the required standard, with all the necessary instrumentation and testing, along with a 5-year warranty.
For procurement engineers that search transformers for their solar or wind interconnection projects, this reference is available on request including full IEEE C57.12.00 test documentation and commissioning details
Your project is too critical for a “one-size-fits-all” catalog price. When grid stability is on the line, you need an engineering partner, not just a supplier. With over 20 years of expertise and thousands of transformers operating worldwide, Daelim Transformer is ready to build your solution from the ground up.
The typical lead time for our 100–500 MVA heavy duty power transformer is around 4 to 8 months, depending on the level of customization and technical specifications. More complex designs or special requirements can extend this period to 8 – 12 months. Final delivery time also depends on testing methods, material availability, and transport arrangements.
When a fault occurs, our team first provides fast remote support. If the fault is within the warranty scope, a repair, replacement of parts or on-site service is arranged. The goal is to ensure the shortest possible downtime and a reliable return to operation as soon as possible.
Yes – Daelim Transformer can manufacture non-standard and fully customized heavy duty transformers. Units are designed according to specific requirements in terms of operating voltage, MVA rating, cooling system and power grid conditions. Tailored engineering covers various demanding domains, such as data center, transmission, power generation, renewable energy sources and industrial systems.
All Daelim Transformer heavy duty transformers are shipped with full logistics support and impact recorders that measure and store all impact data, identifying any unusually severe impacts that could potentially damage the transformer during transportation. In the case of shipping damage, this recorded data provides clear documented evidence to support any insurance or warranty claim, and Daelim Transformer’s aftersales engineering team is available to resolve the issue directly.
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