Oil cooled power transformer for underground installation - is fitted with cage type oil pump motor enclosed inside transformer tank at coolest point

摘要

The application is to underground oil cooled transformers with remote oil coolers. The oil circulation is provided by a pump unit driven by a cage type motor of open construction, both pump and motor being installed at the bottom of the transformer tank and wholly immersed in the cooling oil. the transformer is either buried directly in the ground, or placed in a chamber set in the earth. To reduce bearing wear and improve reliability the motor should have at least two pole pairs in order to keep the speed down. Mounting the motor at the bottom of the tank where the oil is coolest also helps the reability. The transformer oil circulation through the motor provides both cooling and lubrication and, with correct design, no maintenance is required over the life of the transformer.