Analysis of four wire delta center tapped transformer connections

A common loading on a distribution system consists of a combination of single-phase lighting loads and a three-phase induction motor. The lighting loads will consist of two 120 volt loads and one 240 volt load. Four possible transformer bank connections can be used to serve the combination loads. (1) ungrounded wye-delta, (2) grounded wye-delta, (3) "leading" open wye-delta and (4) "lagging" open wye-delta. For each connection the "lighting" transformer will be center tapped to provide service to the two 120 volt and 240 volt loads. This paper uses the "IEEE Four Wire Delta Test Feeder" to analyze the four different connections.