Specifications of Transformer

A transformer should be given along with more than one primary winding or with taps on the winding if it is to be used for various nominal voltages. The Rated Power of the transformer is the sum of the VA (Volts x Amps) for all the secondary windings. The significant specifications for a transformer are: primary frequency of incoming voltage (50 Hz), maximum secondary voltage rating, maximum primary voltage rating, maximum secondary current rating, maximum power rating, efficiency, voltage regulation and output kinds (3 wires or 4 wires).

Transformers in a distribution system could be configured as either single-phase primary configuration (along with three single-phase transformers) or a three-phase configuration (one three-phase transformer). Three-phase transformers are connected in delta (?) or wye (Y) configurations. Although delta configuration is used for three wire transmission and sub-transmission system, wye (or star) configuration is appropriate for 4 wire distribution systems. The wye-delta (Y - ?) transformer has its primary winding linked within a wye and its secondary winding connected in a delta. A delta-wye transformer has its primary winding linked in delta and its secondary winding connected in a wye.