In a three-phase transformer, the basic construction is typically three single-phase transformers in a single tank.

• A. bushings
• B. resistors
• C. single-phase transformers
• D. capacitors

Answer: (C)

Three-phase transformers are often built as a bank of three separate single-phase transformers housed in a single tank. This modular bank approach makes manufacturing and testing easier, and it allows each unit to be replaced or serviced without rebuilding the entire transformer. It also simplifies cooling and insulation, since each unit can be designed and cooled independently while sharing a common enclosure. In practice, the three windings are arranged to provide the three phases, and the bank behaves as a single three-phase device when connected in the proper configuration. The other items listed aren’t describing the basic way a three-phase transformer is constructed—bushings are just the connection points on the transformer, while resistors and capacitors aren’t part of the transformer's fundamental construction.