Dry-Type vs. Liquid Transformers

A transformer enables the use of lower-voltage electricity for various applications. In many cases, powering equipment directly from the main grid isn’t feasible because the voltage is too high. Transformers resolve this by stepping down high-voltage electricity to a lower, usable level suitable for commercial and industrial operations. There are two main types of transformers: dry-type and liquid-filled.

While both types serve the same fundamental function, they differ in characteristics that make them more suitable for specific environments, applications, and budget considerations. If you're designing a power system for a particular project, Tianya Transformers can guide you through the key factors to consider before selecting the right solution.

Dry-Type vs. Liquid-Filled Transformers

Since transformers convert high-voltage electricity into lower, more manageable power, they generate significant heat in the process. Effective cooling is essential—without it, the equipment can overheat and pose safety risks, including combustion.

Air-Cooled Transformers

Dry-type transformers are static electrical devices that use natural air as the primary cooling medium. During the voltage conversion process, heat is generated—this is dissipated through airflow and protected by fire-resistant Dupont Nomex insulation, which helps prevent overheating, fires, and other safety hazards.

These transformers are commonly used in low to medium-voltage applications, making them well-suited for utility, industrial, and commercial settings. Their windings, made from copper or aluminum, are typically sealed with varnish to enhance durability and performance. Various configurations are available to meet specific environmental and operational needs. While dry-type transformers may have a higher initial cost than liquid-filled alternatives, they often yield better long-term profit margins due to lower maintenance and environmental risk.

At Tianya, we design and manufacture dry-type transformers that operate without the use of hazardous cooling liquids. Our advanced copper-wound designs ensure high efficiency, reliable performance, and quiet energy output—making them both cost-effective and environmentally responsible.

We use only high-quality materials and skilled craftsmanship to meet the diverse demands of modern electrical systems.

Liquid-Insulated Transformers

Liquid-insulated transformers, also known as wet-type transformers, use fluid-based cooling methods—typically mineral oil, silicone, or hydrocarbons—along with fans to dissipate heat. These fluids effectively reduce high-temperature hot spots within the transformer coils, enhancing durability and performance. Compared to dry-type transformers, liquid versions are often quieter and are particularly well-suited for medium- to high-voltage applications.

A liquid transformer is typically more efficient than a dry type. A wet type is smaller and needs less demand to make a conversion.

The main difference between a dry type and a liquid transformer is how they cool down. However, there are other variances worth knowing when deciding which is best for your operations.

Safety Requirements and Environmental Considerations: Dry Type vs. Liquid-Insulated Transformers

Dry-type transformers do not rely on toxic or flammable fluids for cooling, eliminating the need for gas ventilation systems and significantly reducing the risk of fire or explosion during overload conditions. Their air-cooled design makes them a safer choice, especially for indoor installations in sensitive environments such as hospitals, schools, and other public facilities. While dry transformers are also suitable for outdoor use, their primary advantage lies in their enhanced safety profile.

From an environmental standpoint, dry-type transformers generate less waste but offer limited options for recycling compared to liquid-filled models.

Liquid-insulated transformers, on the other hand, use flammable dielectric fluids—commonly mineral oil—which provide effective cooling, especially under overload. However, these fluids pose environmental risks if spilled and often require containment systems such as troughs or bunds. Due to the fire and explosion hazards associated with the fluids, liquid transformers are generally not recommended for indoor use. If used indoors, additional safety measures must be in place to mitigate fire risk and limit human exposure to the dielectric fluid.

Some modern liquid-insulated transformers use alternative fluids like silicone, natural esters, or hydrocarbons. These options may be non-toxic, biodegradable, renewable, and feature higher flashpoints, making them safer and more environmentally friendly.

While dry-type units are safer and more straightforward in terms of waste management, liquid transformers offer broader opportunities for recycling and remanufacturing. Components such as the coil and core can often be replaced, reclaimed, or recycled, and the insulating fluid can be reconditioned and reused. Salvaging materials like copper, aluminum, and steel is also feasible—though local regulations should be consulted.

In summary, dry transformers prioritize safety and low environmental impact during operation, while liquid-filled units offer greater recyclability and long-term material recovery potential.

Dry Type vs. Liquid Type Maintenance

Maintenance requirements for dry-type and liquid-filled transformers differ significantly, with dry-type transformers generally being simpler to maintain.

Dry-Type Transformers:

These air-cooled units primarily require regular visual inspections. The frequency of inspection depends on the load and usage intensity—greater use demands more frequent checks. Although dry-type transformers are less susceptible to contamination, it’s essential to monitor for dust accumulation. Clean the windings, grilles, and coils using compressed air, a vacuum, or a blower.

Additionally, inspect for loose connections, which can affect performance. Despite their relatively straightforward upkeep, dry-type transformers may incur higher maintenance costs in certain cases due to limitations in size and voltage capacity, which can increase the risk of overheating under heavy loads.

Liquid-Filled Transformers:

These transformers require more comprehensive maintenance due to the presence of insulating fluid. Like dry units, begin by inspecting and tightening all electrical connections. Next, check fluid levels, gauges, and look for signs of leakage. A reading of zero pressure can indicate a potential leak, which may require immediate attention in line with local, state, and federal regulations if a spill occurs.

Leaks can also result from worn components such as gaskets—replace any deteriorated parts promptly. In addition, perform fluid sampling to assess the condition of the insulating liquid. A Dissolved Gas Analysis (DGA) test can help detect issues such as moisture, contamination, dielectric strength, and the presence of flammable gases. If gas levels exceed acceptable thresholds, the fluid may need to be filtered or replaced.

Compared to dry-type models, liquid-filled transformers demand more frequent and thorough maintenance to ensure optimal performance and safety.