E & E / Dry Type Transformers

Dry Type Transformers

During operation the wire-coils in a transformer generate heat. This heat needs to be removed from the transformer to prevent the insulating material from deteriorating and the transformer from operating less effectively. Traditionally this heat is removed from the transformer by having a liquid cooling fluid running through the transformer. The fluid also functions as the insulator. Dry Type Transformers are power transformers where the windings are encased in heat conductive (and electrically insulating) epoxy resin and the heat is removed by a flow of air.

The resin-compound needs to have good flowability and be easy to de-air. The epoxy casting also protects the transformer against harsh (environmental, e.g. high relative humidity) conditions and reduces the level of maintenance needed to keep the transformer delivering peak performance. These transformers can often be found in high-rise buildings, hospitals, road and underground railway shafts, offshore installations, mines and other critical infrastructure.

Sibelco’s mineral fillers provide the following properties to epoxy resin:

  • Flame retardancy (ATH)
  • Mechanical strength (Silica)
  • Dimensional Stability (Silica)
  • Low viscosity (Silica and ATH)
  • Electrical insulation (Silica and ATH)
  • Thermal conductivity (Silica)


Sibelco has an extensive offering of ground Silica Flour & ATH products, allowing the customer to select the right combination for the application requirements of the epoxy resin formulation.