Three-Phase Transformers

Author: E.E. Kimberly

Three-phase transformers, instead of groups of three single-phase units, may sometimes be used with convenience and economy. These transformers consist of three separate windings mounted on a three-legged or four-legged core. They are lighter and lower in cost, require less floor space, and are more efficient than three single-phase transformers of equivalent capacity. However, their greater cost of repairs, the greater cost of spare units, and the greater derangement of service in case of failure weigh so heavily against their installation that groups of three single-phase units are more commonly used. Fig. 17-13 shows a three-phase transformer on which the coils are assembled on three magnetically interconnecting cores.

Fig. 17-13. Elements of Y-Connected, Three-Phase Transformer With Three Magnetically Interconnected Legs