Tank construction can be of any type mentioned below.
Hermetically Sealed without gas cushion
Sealed with gas cushion
Conservator type with breather
Cooling with corrugated fin
Cooling with radiator
Transformers are manufactured according to IEC 60076 in general and in particular as per concerned Utility / Client Specifications.
The magnetic circuit (Fig.1) is made of a high quality cold rolled, grain oriented silicon steel strips. Each strip is insulated from both sides by Carlite and is cut with an angle 45⁰. Step lap and conventional mitered joint stacking is employed to reduce the no-load losses and the exciting current.
Both the Low Voltage and High Voltage windings (Fig.2) are made of copper. (Aluminum winding can also be provided upon special request). The high Voltage winding is wound directly on the Low Voltage winding, with insulating paper and cooling duct, between the two windings. Most modern techniques are used to provide adequate short circuit strength.
Tappings are provided on the HV windings (number and step according to client requirements) with standard values of ±2.5% & ±5%. The step change from one tapping to another is done by operating an offload tap changer. Padlock for tap changer handle can be provided.
For dual primary voltages (e.g. 13.8 – 11, 11- 6.6 KV), the switching from one primary voltage to the other is done by a voltage selector.
Transformers are supplied filled with mineral oil according to IEC 60296 – Class I. In addition Silicon or Midel oil can be provided on request.