You might be wondering what makes dry type transformers a preferred choice in so many industries. Well, it’s all about their unparalleled safety, reliability, and environmental advantages. Unlike their oil-filled counterparts, dry type transformers don’t use a cooling liquid, making them a safer option in environments where fire hazards are a concern. They’re built tough too, capable of withstanding harsh conditions like high humidity, fire risks, and even seismic events, all without skipping a beat in performance.
These transformers are not just about handling tough situations; they also play a significant role in protecting both people and property by minimizing risks associated with leaks and spills.
In this blog post, we’ll dive deep into the world of dry type transformers. Let’s get started straightaway.
Understanding What is Dry Type Transformer
Unlike their liquid-filled counterparts, dry-type transformers don’t rely on oil or other liquids for cooling. Instead, they utilize natural air circulation or employ fans to dissipate heat generated during operation. In a dry-type transformer, the construction of the coils is fundamentally different from those in liquid-filled transformers. The coils in dry-type transformers are not submerged in cooling fluids. Instead, they are insulated with solid materials such as resin, which can handle high temperatures without the risk of catching fire or leaking harmful substances.
This design is crucial for the safety and environmental aspects of these transformers. The solid insulation medium, often a combination of synthetic resins and varnishes, not only protects the coils but also efficiently manages the heat generated during operation. The use of a dry or gaseous medium ensures that the transformer can be safely installed in indoor and environmentally sensitive locations without the risk of fluid leaks or spills, which are concerns with oil-filled transformers.
Most Common Types of Dry Type Transformers
The most common dry type transformers are:
Vacuum Pressure Impregnated Transformer (VPI)
The Vacuum Pressure Impregnated (VPI) transformer represents a significant advancement in transformer technology, employing an innovative technique where class H polyester resin is used to saturate the windings under a controlled environment of vacuum and pressure. This process meticulously removes all air gaps and voids within the insulation, considerably enhancing the transformer’s overall mechanical strength, its ability to withstand electrical stresses (dielectric strength), and its thermal endurance.
The design and build of VPI transformers make them exceptionally suited for challenging external conditions. They are built to perform reliably in outdoor environments, capable of handling extreme seismic activities, and are resilient against temperature fluctuations. The enclosure of these transformers is designed to be moisture-resistant, featuring a low coefficient of thermal expansion, which contributes to their longevity and reduces maintenance needs.
Safety is another paramount advantage of VPI transformers. They are known for their low fire risk and exhibit high resistance to short circuit currents, adding an extra layer of security for operators and installations alike. This makes them particularly valuable in industries where safety and reliability are critical.
VPI transformers are versatile in their applications, available in a range of power capacities from 5 kVA to 30 MVA. They are offered with two levels of insulation—class F (155°C) and class H (180°C)—and can be equipped to meet up to IP56 standards for ingress protection, which guards against dust ingress and powerful water jets, further asserting their suitability for harsh operational environments.
Cast Resin Dry Type Transformer (CRT)
The Cast Resin Dry Type Transformer (CRT) employs a distinctive encapsulation method where both primary and secondary windings are encased in epoxy resin. This encapsulation serves as a robust barrier against moisture, dust, and corrosion—common environmental threats that can degrade insulation and diminish performance.
Optimized for durability and safety, CRTs are particularly advantageous in settings prone to high humidity, such as indoor areas, and locations where fire risks are a concern. The non-hygroscopic and non-flammable nature of the resin, coupled with the maintenance-free design of these transformers, ensures a stable, efficient operation. CRTs are also designed to handle electrical overloads and partial discharges effectively, while maintaining low operational losses. This combination not only boosts the overall efficiency but also significantly extends the service life of the transformers.
These transformers are available in a range of capacities, from modest 25 kVA models suitable for smaller facilities, up to large 12,500 kVA units ideal for extensive industrial applications. They come with an insulation class of F, allowing for a temperature rise of up to 90°C, which further underscores their robustness and adaptability in varied environmental conditions.
Common Dry Type Transformer Configurations
Dry-type transformers come in various configurations to suit different applications. Some of the most commonly used ones are:
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General Purpose Ventilated Transformers
Ventilated transformers, ideal for commercial and minor industrial uses, come in both single and three-phase varieties. These units are typically available in sizes ranging from 15 kVA to 1000 kVA. They operate with primary voltages between 380 V and 575 V, and secondary voltages from 120 V to 240 V. Constructed with either aluminum or copper winding, they are insulated to withstand up to 220°C. These transformers function efficiently within a temperature rise range from 80°C to 150°C and are compatible with electrical systems operating at 50 Hz or 60 Hz.
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General Purpose Encapsulated Transformers
These are commonly utilized in a variety of industrial and light industrial applications. These transformers, available in both single and three-phase variants, feature dual winding systems encapsulated in a robust mixture of epoxy-coated sand and gravel. They are typically available in capacities ranging from 0.05 kVA up to 75 kVA, with primary voltage options from 380 V to 575 V and secondary voltages between 120 V and 240 V.
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Totally Enclosed Non-Ventilated Transformers
These are ideal for environments where there are conductive, corrosive, or combustible materials, as well as lint and dust that could obstruct ventilation paths. These transformers are completely sealed, allowing heat to escape through the enclosure’s surface area. They typically vary in size from 15 to 300 kVA and offer primary voltages from 380 to 575 V and secondary voltages from 120 to 240 V. Operating efficiently within a temperature rise range from 80°C to 150°C, these transformers can handle both 60 Hz and 50 Hz frequencies.
So, there you have it. If you have any queries or need further assistance, please don’t hesitate to contact us. We look forward to assisting you.
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