Cast Resin & Open Wound Dry Type Transformers


Different Dry-Type Transformers

Dry-type transformers, have no moving parts, are stationary equipment that uses environmentally friendly insulation systems. Traditional liquid-type transformers rely on materials such as flame retardant oil or liquid dielectric. “Dry” refers to the fact that the system is cooled through natural ventilation rather than using oil, silicone, or liquid to cool the coil and the electrical core. This type of transformer is defined as a “voltage change”, which means the air is cooled instead of liquid-cooled. The case of the transformer is placed inside is ventilated so that the air can cool the coil.

Unlike liquid transformers, dry-type transformers do not need to be placed inside fireproof vaults or storage tank, and you don’t have to worry about releasing toxic gas out. Since dry-type transformers are much safer, they can be placed indoors and closer to load, making the whole system more efficient.

There are different types of dry transformers available on the market.

  • Open Wound Transformer
  • VPI-Vacuum Pressure Impregnated
  • VPE-Vacuum Pressure Encapsulated
  • Cast Coil

Open Wound Transformer

This type of transformer is named through its manufacturing process, including the “dip and bake” method. The coils are heated, immersed in varnish at a high temperature, and then heated, known as the open-wound method.

VPI (Vacuum Pressure Impregnated) Transformer

VPI transformers are commonly used for commercial and industrial use. They have high-temperature insulation that ranks above the ‘O’ and ‘K’ liquid classifications. VPI transformers are made from materials that withstand high temperatures and moisture-resistant polyester glue commonly applied by the vacuum pressure impregnation technique. For the most part, they are rated up to 30 MVA.

Vacuum Pressure Encapsulated (VPE) Transformer

VPE are made from silicon-based plastic, which creates a thicker coating that is highly resistant to moisture and harsher environments susceptible to acids, chlorides, and alkalis.

Cast Coil Transformer

These transformers work in extreme weather conditions, so they require very little maintenance, and they are highly resistant to short circuits. These transformers are used in ships, tunnels, nuclear plants, cranes, and the mining industries.

Cast Resin Transformers

• Cast resin transformers are self-extinguishing and low fire hazard
The transformer’s insulation consists of an epoxy resin and quartz powder mixture (an eco-friendly material). They prevent the winding from fire. They are almost maintenance-free, so you don’t need to buy costly fire extinguishing equipment. Moreover, the cast resin transformer will also not produce toxic gases, not even effected by arcing.

Zero oil usage:
It only needs air to cool the coil. Therefore, you don’t need to pay extra costs and labor for liquid-level checking, oil testing, oil recycling costs, and dielectric testing for moisture absorption. Because they are almost maintenance-free, there are no oil leaks when operating, which require gasket replacements.

Safe and environment friendly:
Cast resin transformers do not create any risk for oil leaks and environmental pollution. During normal operation, transformer explosions are highly unlikely due to utilizing self-extinguishable non-toxic substances, even having external fires. They are also suitable for heavy condensation, wet and polluted environments. The transformers may also withstand abrupt environmental changes from -25ºC to +40ºC in a short time. 

Low-cost installation and lower load losses:
There are almost no restrictions when on the installation site. The closer the transformer is to the load, the lower the cable losses and cost.
• Reliability: Cast resin transformers have a life cycle of more than ten years and a low failure rate when operated within its designed parameters. This makes it a highly reliable component that is suitable for any electrical infrastructure. You can contact Vietnamtransformer for more information about the cast resin transformer. 

Low maintenance cost:
Cast resin transformer only needs air to cool, and liquid testing becomes unneeded. Its smooth coil surface eliminates massive dirt build-up, even in the most extreme circumstances. You only need technical personnel to clean and visually check it. 

High short-time overload capacity:
Cast resin transformers can handle short-time overloads far better than oil-cooled units as the windings of cast resin transformers are encapsulated in resin, so the effects of axial and radial forces under high current loads are eliminated. 

Historically, the cracking of cast resin transformers shorter life cycles, so the latest technology has introduced glass fiber reinforcement in the windings that eliminate cracking by its heating and cooling curves.

Low noise levels:
Due to flexible winding supports and design flux densities, they reduce the noise levels during operation.

Compact design:
By the nature of the design, cast resin transformers are more compact so that they require less space than oil-cooled units.

Cast resin transformer contribute to saving our natural resource. Their structure and operation are environment friendly.

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