Are you concerned about the safety and reliability of your electrical power systems? Traditional liquid-filled transformers can pose risks like leaks, fires, and environmental contamination.
Dry-type transformers provide a robust, low-maintenance solution for industrial power needs, with enhanced safety features, excellent efficiency, and a compact footprint compared to liquid-filled alternatives.
What is a Dry-Type Transformer
A dry-type transformer is an electrical transformer that uses air as the cooling medium instead of oil or other liquid dielectric. In a dry-type transformer, the windings and core are not immersed in insulating liquid. Instead, the transformer relies on natural air circulation or forced air cooling to dissipate heat generated during operation.
Types of Dry-Type Transformers
Ventilated Dry-Type Transformers
- Open Wound: In this type of transformer, the windings are exposed to the surrounding air, allowing for natural convection cooling. The windings are typically made of enameled copper wire with insulation between layers.
- Vacuum Pressure Impregnated (VPI): VPI transformers have windings that are impregnated with a high-quality varnish or resin under vacuum and pressure. This process fills the voids between the windings, improving insulation and heat dissipation.
- Vacuum Pressure Encapsulated (VPE): VPE transformers have windings that are completely encapsulated in a solid insulating compound, such as epoxy resin or silicone rubber. This provides excellent mechanical and moisture protection, as well as improved thermal performance.
Encapsulated Dry-Type Transformers
Encapsulated dry-type transformers have their windings and core completely sealed in a protective enclosure filled with a solid insulating compound, such as epoxy resin or silicone rubber. This type of transformer offers superior protection against environmental factors, such as dust, moisture, and chemical contaminants.
Non-Ventilated Dry-Type Transformers
Non-ventilated dry-type transformers are designed for use in hazardous locations or harsh environments where ventilation is not possible or desirable. These transformers rely on conduction and radiation to dissipate heat, and their windings are usually encapsulated in a solid insulating compound to provide additional protection.
Components of a Dry-Type Transformer
- Core: The transformer core is made of high-quality, grain-oriented silicon steel laminations. The laminations are stacked and bonded together to form the core, which provides a low-reluctance path for the magnetic flux.
- Windings: The primary and secondary windings are made of insulated copper or aluminum conductors. The windings are arranged concentrically around the core, with the primary winding connected to the input voltage source and the secondary winding connected to the load.
- Insulation: The windings are insulated using materials such as enamel, varnish, or resin, depending on the transformer type. The insulation provides electrical isolation between turns, layers, and windings, as well as protection against moisture and contaminants.
- Cooling System:
- Natural Convection: In smaller dry-type transformers, heat is dissipated through natural air circulation around the windings and core.
- Forced-Air Cooling: Larger dry-type transformers may require forced-air cooling using fans to increase the heat transfer rate and maintain acceptable operating temperatures.
- Enclosure: Dry-type transformers are housed in a protective enclosure, which may be open, ventilated, or sealed, depending on the application and environment. The enclosure provides mechanical protection and may also help with noise reduction.
- Terminals and Bushings: High- and low-voltage terminals or bushings are used to connect the transformer windings to the external circuitry. These terminals are designed to withstand the rated voltage and current of the transformer.
- Grounding System: Dry-type transformers are equipped with grounding points to ensure proper grounding of the core and enclosure, as required by safety regulations and standards.
- Temperature Monitoring and Protection: Many dry-type transformers include temperature monitoring devices, such as thermocouples or RTDs, to measure the winding and core temperatures. These devices are connected to protective relays that can trigger alarms or initiate a shutdown if the temperature exceeds safe limits.
