Car wiring diagrams: 3 Phase Transformer Diagram, wiring diagram, wire wiring harness, schematic circuit diagram, wiring diagran, wireing diagram, wirring diagram, wiring daigram, wiring diagrams. In the star star arrangement Yy , wye wye , each transformer has one terminal connected to a common junction, or neutral point with the three remaining ends of the primary windings connected to the three phase mains supply..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. Essentially it looks like three single phase transformers sharing a joined core as in Figure below. Three phase transformer core has three sets of windings..Three phase transformer connections In three phase system, the three phases can be connected in either star or delta configuration. In case you are not familiar .