Epoxy Resin Cast Dry-Type Transformers: What Exactly are They? What Do They Do?

I. What is an Epoxy Resin Cast Dry-Type Transformer?

Epoxy resin dry-type transformers use epoxy resin as the insulating material. The high and low voltage windings are wound with copper tape (foil), and epoxy resin is poured and solidified in a vacuum to form a high-strength fiberglass structure. The insulation grades are F and H. Dry-type transformers rely on air convection or forced air cooling for heat dissipation and do not have transformer oil. 

Due to its fireproof, explosion-proof and maintenance-free properties, it is widely used in urban subways, high-rise buildings, airports, hospitals, commercial centers and other places with high fire and safety requirements.

II. Process Characteristics of Epoxy Resin Cast Dry-Type Transformers

1. Winding casting molding: The high and low voltage winding are cast with epoxy resin mixture in a vacuum state, and form a dense and solid whole after solidification.

2. Insulation system: It mainly uses epoxy resin as the main insulation and glass fiber as the reinforcing material. It does not require insulating oil and is a solid insulation equipment.

3. Cooling method: usually AN (natural air cooling) or AF (forced air cooling). Equipped with a temperature controller and an axial flow fan, the fan can be started and stopped automatically according to the load temperature. Some products allow short-term overload operation.

III. The Main Advantages and Disadvantages of Epoxy Resin Cast Dry-Type Transformers

Advantages:

1. High Safety and Environmental Friendliness

• Fire and explosion-proof: Epoxy resin itself is a flame-retardant, flame-retardant and self-extinguishing material, which fundamentally eliminates the risk of fire and explosion.
• Pollution-free: Does not contain any insulating oil, eliminating the possibility of oil leakage contaminating soil and water sources. It is very clean.

2. Excellent electrical and mechanical properties

• High insulation strength: The cured epoxy resin forms a dense insulation layer with good insulation performance and strong lightning impact resistance.
• Strong short-circuit resistance: The coil is solidified into a high-strength rigid whole with extremely high mechanical strength and can withstand the huge electrodynamic impact generated when a sudden short circuit occurs.

3. Excellent environmental adaptability

• Moisture-proof and dust-proof: The sealed resin layer can effectively isolate moisture, dust and corrosive gases, and can even operate normally in an environment with 100% humidity.
• Low maintenance cost: No preheating is required before operation, and no drying treatment is required after shutdown. Daily maintenance workload is minimal.

4. High efficiency, energy saving and compact design

• Low loss: By optimizing the iron core (such as using high-quality silicon steel sheets) and winding design, no-load and load losses are very low, and the energy saving effect is significant.
• Small size and light weight: Thanks to the high insulation efficiency of epoxy resin, its size and weight are much smaller than oil-immersed transformers of the same capacity, saving installation space and civil construction costs.
• Low noise: Using advanced technology and materials, the operation noise is low, suitable for hospitals, residences, etc. that are sensitive to noise.

Disadvantages:

• Temperature resistance is relatively limited: commonly used insulation grades are F (155℃) or H (180℃), long-term operating temperatures are usually limited to around 120℃~140℃, and the overload ability is not as good as that of oil-immersed type.
• Risk of partial discharge and cracking: If the pouring process is not strictly controlled (such as bubbles and uneven mixing), partial discharge may easily occur; under extreme cold and hot changes or mechanical stress, epoxy resin may have a risk of cracking.
• High cost: The initial acquisition cost is usually higher than that of oil-immersed transformers of the same capacity.

IV. Maintenance and Common Faults of Epoxy Resin Cast Dry-Type Transformers

• Daily key points: Pay attention to appearance (cracks, discharge traces), temperature (temperature control/hot spots), and abnormal noise; keep insulators, winding surfaces and air ducts clean to prevent dust accumulation from affecting heat dissipation and insulation.
• Regular inspection/testing: insulation resistance, DC resistance, AC withstand voltage, partial discharge, etc.; fastener and grounding inspection are also critical.

Typical Issues:

• Winding Overheating: Often related to overload, poor ventilation, or aging; may manifest as discoloration of the epoxy, burning smell, or localized overheating.
• Partial Discharge: Can originate from damp/damaged insulation, poor leads/grounding, etc., and accelerates aging over time.
• Unusual Noises/Vibrations: May be associated with core clamping issues, loose fasteners, load harmonics, resonance, etc.

V. Common Technical Parameters of Epoxy Resin Cast Dry-Type Transformers

The following are some common technical parameter ranges for epoxy resin cast dry-type transformers, and the specific values will vary depending on the model and manufacturer:

Our company has epoxy resin cast dry-type transformers available for selection.

VI. Main Application Areas of Epoxy Resin Cast Dry-Type Transformers

Epoxy resin cast dry-type transformers are particularly suitable for the following places with high safety and environmental requirements:

• Urban public facilities: high-rise buildings, commercial centers, airports, subway stations, tunnels, sports venues, etc.
• Important institutions: hospitals, data centers, theaters, schools, laboratories, etc. to ensure the continuity and reliability of power supply.
• Industrial environment: Chemical plants, nuclear power plants, mines, power plants and other harsh environments where flammable, explosive or corrosive gases exist.
• New energy fields: wind power generation, photovoltaic power stations, etc.