HomeMagazine ArticleAdvantages of cast resin dry-type transformers

Advantages of cast resin dry-type transformers

By Morné Bosch, general manager for sales and marketing at ArmCoil.

When researching the advantages of cast resin dry-type transformers, you may find the information available to be somewhat incomplete. More so, only a few of its favourable features are well known, with one of the most noteworthy being its minimal fire risk due to zero oil usage.Cast resin transformer

Self-extinguishing, low fire hazard:

The transformer insulation consists of an epoxy resin and quartz powder mixture (an eco-friendly material). This allows the winding to be flame-retardant, selfextinguishing and almost maintenancefree, eliminating the need for costly fire extinguishing equipment. It will also not produce toxic gases, not even under the effects of arcing.

Zero oil usage:

The cast resin transformer only needs air to cool. Therefore, it eliminates extra costs and labour for liquid-level checking, oil testing, oil recycling costs, and dielectric testing for moisture absorption. Being almost maintenance free, there are no more on-site oil leaks, which require gasket replacements.

Eco-friendly and safe:

Cast resin transformers pose ZERO risk for oil leaks and pollution of the environment. Transformer explosions during normal operation are highly unlikely due to the selfextinguishable non-toxic substances utilised, even during external fires. They are also suitable for heavy condensation and polluted environments. Cast resin transformers may also withstand abrupt environmental changes from -25ºC to +40ºC in a very short time. TIP: Always try to ensure that your preferred manufacturer has passed/ obtained C2/E2/F1 tests according to IEC 60076-11 and that it is approved, i.e. KEMA type tested.

Low cost installation and lower load losses:

There are almost no restrictions on the installation site. Furthermore, there will be no groundwater protection costs during site preparation. The closer the transformer is to the load, the lower the cable losses and cost. Reliability: Cast resin transformers have a service life expectancy of 20+ years, and a low failure rate when operated within its designed parameters. This makes it a highly reliable component of any electrical infrastructure. For proven reliability statistics and case studies, please contact ArmCoil for further information.

Low maintenance:

Cast resin transformers only need air to cool, and liquid testing becomes obsolete. Its smooth coil surface eliminates heavy dirt build-up, even in the most extreme circumstances. The only recommended maintenance is a routine visual inspection by technical personnel, and a wipe down of the transformer as required.

High short time overload capacity:

As the windings of cast resin transformers are encapsulated in resin, the effects of axial and radial forces under high current loads are eliminated. Therefore, cast resin transformers are able to handle short time overloads far better than oil cooled units.


Due to historical cracking of cast resin transformers, the latest technology has introduced glass fibre reinforcement in the windings that eliminates cracking due to its heating and cooling curves.


The complete embedding of the transformer winding in resin prevents the penetration of moisture. This results in low maintenance and an extended transformer life.

Low noise levels:

Due to design flux densities and flexible winding supports, the noise levels during operation are reduced by a considerable amount.

Compact design:

By the nature of the design, cast resin transformers are more compact and require less space than oil cooled units.


Using cast resin transformers contributes to saving our resources. Its design and operation is considerate of the environment through: • A long service life of 20+ years, • Its low loss levels; meaning it uses less electricity, and • 90% recyclable transformer materials; meaning less waste. It should be noted that the choice between a cast resin and oil-cooled transformer is always application dependent. However, before making a decision, all requirements of the environment and operating conditions need to be taken into consideration. Today, we live in a world where initial cost is no longer the most important factor, with long-term costs on the environment deserving serious contemplation. Considering the advantages of cast resin dry-type transformers, and the increasing rate of natural resource extraction – which would you say is the better choice?


15 Advantages Of Cast Resin Dry-Type Transformers. By Inge Webber, marketing assistant for RMM Project Engineers.

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