G. DELTA - WYE: 4-Wire, 3-Phase Service
A B C N
H1 H2
H1 H2
H1 H2
X3
X1
X3
X1
X3
X1
Tank GND
Tank GND
Tank GND
X2
X2
X2
a b c n
Primary Wiring - DELTA: With a Delta connected high-voltage side, the H1 terminal of each transformer is connected to the H2 terminal of the adjacent transformer in circular fashion. These H1/H2 pairs are then connected to the primary phases. System neutral connected to the transformer tank and secondary neutral/ ground. Secondary Wiring – WYE : Transformers banks with this secondary configuration are widespread and used to service both single-phase and three- phase loads. Common service voltages are 208Y/120V and 480Y/277V. Occasionally, 416Y/240V and 830Y/480V services will be seen and can be accommodated with this bank configuration. Transformers used for the 208Y/120V service must be “split” by opening the transformer top, splitting the winding leads and connecting them in parallel.
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