Inherent Voltage Relations in Y and Delta Connections

The paper gives the results of experiments made with a miniature simple transmission system to demonstrate the inherent voltage relations with different combinations of Y and delta connections. The experimental system consisted of a 7.5-kv-a. revolving field generator, with coil terminals which could be connected either Y or delta, and two banks of transformers each composed of three shell-type 3-kv-a. units. All inductive and capacity effects in the transmission line were eliminated. The tests were made under constant conditions, with non-inductive load. The authors give the results of four groups of tests, on four different systems of connections, pointing out the advantages and disadvantages of the several systems. In each case tests were made without load, with balanced load, and with load on one phase only, for various conditions of grounding. Typical voltage diagrams are given, to show what happens under various conditions of load. The authors discuss certain cases where the use of auto-transformers is advantageous, and the effects of different ways of connecting them.