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Transformer oils (insulating oils)

Dr. Dmitri Kopeliovich

Transformer oils (insulating oils) are dielectric oils used in oil-filled transformers, some high voltage capacitors and circuit breakers, fluorescent lamp ballasts.

Oil-filled transformers are more efficient, more reliable more compact, more quiet and with longer lifespan than dry transformers.

Transformer oils have the following functions:

  • Prevention of electrical discharges between the transformer coils: corona and arc (insulating).
  • Removal of heat generated by the transformer (cooling). Transformer oil forced by natural convection circulates through a radiator carrying the heat out of the transformer.


Transformer oils (insulating oils) have replaced toxic PCB (polychlorinated biphenyl).

Mineral oils, vegetable lubricants (soybean oil, vegetable based esters) or synthetic lubricants (polydimethylsiloxane) are used as basics for transformer oils.

Properties of some transformer oils

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transformer_oils_insulating_oils.txt · Last modified: 2012/06/02 by dmitri_kopeliovich
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