Three-legged cores made of cold-rolled, low power loss transformer plates covered with inorganic insulating material. Stepped cross-section of the core leg is nearcircular with optimal structure designed with the aid of computer software, taking into account the cross-section filling factor and suitable flux density. Both leg and yoke sheets made in the form of strips with chamfered ends are carefully assembled in packets, thus ensuring reduction of no-load losses and noise level. In the splicing area several sheets are mutually offset by several millimeters and form so called Step-Lep cycles.
The windings of transformers are made of electrolytic copper with paper insulation consisting of several up to a dozen or so parallel conductors. The cooling system is usually made in the form of wedges and inserts made of insulating pressboard.
The transformer is equipped with in-built on-load tap changer on the HV side. The tap changer is operated by 3×400/230 V, 50 Hz electric motor. Control voltage is 230V, 50 Hz. The tap changer drive can be electrically controlled, both remotely and locally. Moreover the tap changer can be operated manually by using a crank. The tap changer drive is equipped with tap position indicator.
The tank with no additional equipment can withstand the pressure difference between inner and outer pressure equal to ±500 hPa. The tank design allows lifting the transformer by using hydraulic jacks or by overhead travelling cranes or other types of cranes. The tank is coated with lacquer resistant to atmospheric conditions.
Capacity: 2.5-80 MVA
Voltage levels: 6-132 kV