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Specialist Materials for Industry and Science

Transformer Oils

Transformer Oils

Properties of Synthetic and Natural Ester Transformer Oils

Transformer oils are ideal for minimising electrical clearances and augmenting cooling performance in a variety of applications.

Previously, mineral oils were thought to be the best way of achieving optimum transformer performance, but research has since revealed these to be highly flammable and bad for the environment, while they also contain corrosive sulphur and have a poor moisture tolerance.

The Midel range uses both natural and synthetic esters as a mineral oil alternative for transformers, achieving the same goal safely in an environmentally friendly way.

Natural Ester Fluids

MIDEL eN is a natural transformer ester oil, making it particularly good for those seeking an environmentally sound solution to their dielectric fluid requirements.

It is made using renewable materials, and in the event of a leak or spillage its biodegradability greatly reduces the potential damage caused to the surrounding area. MIDEL eN has also been found to be non-corrosive by independent laboratories, while it has a very high fire point and is fully RoHS compliant.

This ester is suitable for sealed transformers, and works best in temperate climates, making it a particularly good option for distribution transformers in built-up areas and indoors.

Synthetic Transformer Ester Oils

Synthetic transformer ester fluid MIDEL 7131 is a reliable, flexible product with a strong track record of performing well in a wide range of applications, particularly in challenging situations such as offshore or underground.

Like MIDEL eN, MIDEL 7131 has been found to be non-corrosive and environmentally friendly. It also has a high fire point of over 300°C and is very low maintenance, earning a reputation as the 'fill and forget' fluid.

It works well in both sealed and breathing transformers, and can be used successfully in power transformers, rectifier transformers, pole-type transformers and traction transformers, making MIDEL 7131 the most versatile dielectric fluid on the market.

Find Out More About Midel Esters

If you would like more information on Midel esters and their properties, you can contact us or consult our documents for answers to all your questions.



  • Apiezon
  • Metrosil
  • Midel
  • Wolfmet

Products of M&I Materials Ltd.