Oil Cooled Transformer

Oil Cooled Transformer Technical Specification


The core is made exclusively of cold-rolled grain-oriented sheet coated with magnesiumsilicate-phosphate insulation on both sides.

To full utilize the grain orientation of the laminations, the ends of the limbs and yokes are mitered and stacked together by overlapping the laminations in pairs, which will reduce the no-load losses and thus the power required for magnetizing the core.

The core will be rigidly clamped with positive locking devices to ensure adequate mechanical strength to support the winding and also to prevent shifting of laminations during transport and further to reduce vibration to minimum during operation.


The winding will be made of round section electric copper covered with several layers of ageresisting insulation paper or enamel coating high dielectric strength.

Sufficient cooling channels between windings will be provided and all winding will be constructed firmly to be sustained from external and internal mechanical stress.


The transformer will be enclosed in a suitably stiffened welded steel tank such that the transformer can be lifted and transported without permanent deformation or oil leakage.

Lifting lug will be provided, suitable for the weight of the transformer, including core and windings, fittings, and with the tank filled with oil. The base of tank will be so designed that it is possible to move the complete transformer unit in any direction without injury when using rollers, plates, or rails.


Corrugate type radiator will be provided to sufficiently cool down the heat generated by transformer loss.


The electrical strength of insulating oil will be reduced by the water contamination caused by air in contact with the oil.

Adequate oil preservation system will be mentioned in technical specification for protecting the insulating oil from atmospheric moisture contamination in accordance with the capacity and the voltage class of transformer.


Dried and degassed insulating oil will be filled in the transformer tank by oil treatment plant.

The insulating oil type will be mentioned in technical specification. : IEC 60296(U- type)


All surface will be thoroughly cleaned by sand blasting or shot blasting before painting and coated with priming coat immediately afterwards, followed by two further coats of oil and water resisting paint of a high quality.

Refer to enclosed painting procedure for transformer : RAL 7032