In the 1880’s the development of transformers contributed essentially to the enforcement of alternating and three-phase current technology. Transformers enable the transmission of electrical energy using the voltage adapted to power and distance. A three-phase transformer is made of three sets of primary and secondary windings, each set wound around one leg of an iron core assembly. A three-phase transformers must have (3) coils or windings connected in the proper sequence in order to match the incoming power.

Three-Phase delta wye Circuits Diagram Three phase transformer core has three sets of windings. Those sets of primary and secondary windings will be connected in either ? (delta) or Y (wye) configurations to form a complete unit. The three primary windings (P1, P2, P3) will be connected at the factory to provide the proper sequence (or correct polarity) required and will be in a configuration known as Delta. The three secondary windings (S1, S2, S3) will also be connected at the factory to provide the proper sequence (or correct polarity) required.

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Three-Phase Transformers Circuits Diagram – link (source:
3 Phase Electrical Power Transformer – link (source:
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