H. OPEN WYE – OPEN DELTA: 4-Wire, 3-Phase Service
A B C N
H1 H2
H1 H2
X3
X1
X3
X1
Tank GND
Tank GND
X2
X2
a b c n
Primary Wiring - WYE: For the Open WYE – Open DELTA is very similar to the WYE – DELTA, except it utilizes two of the three transformers. The H1 terminals are connected to different primary phases. But unlike the WYE – DELTA, on the OPEN WYE – OPEN DELTA transformer bank, the H2 terminals are connected together, they must be solidly grounded, and not allowed to float. Secondary Wiring: This secondary connection supports both single-phase and three-phase loads. 240∆/120 banks are popular due to their ability to serve multiple customer types from the same transformer bank: single-phase for customers with lighting and small motor loads, and three-phase for
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