Delta-cross connections of transformers for parallel operation of two- and three-phase systems

Two methods of transformer connections, the tee-cross and the delta-cross, are described with their application for parallel operation of two-phase and three-phase systems. An attempt is made to explain as clearly as possible the voltage, current and phase relation, and the dephasing action which take place in each case. The delta-cross system of connections lends itself to a great number of applications, either for the parallel operation of two-phase and three-phase systems or for the simultaneous supply of two-phase and three-phase power from one bank of transformers. It is to be noted that in this system of connections no special taps are required, except a 50 per cent tap on one transformer (usually easily obtainable), the compensation of one phase of the system being done externally by means of a small booster transformer. The simplicity of connections, the feature that no special transformers are required, and no special taps necessary, give the electrical engineer facilities to meet promptly and economically the requirements inherent to two-phase and three-phase simultaneous distribution from only one transformer bank.