E. DELTA – DELTA: 4-Wire, 3-Phase Service
A B C N
H1 H2
H1 H2
H1 H2
X3
X1
X1
X3
X1
X3
X2
Tank GND
Tank GND
Tank GND
X2
X2
a b c n
For this type of transformer bank, two bushing conventional transformers of equal kVA rating are to be used. Primary Wiring: 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. 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 other customers who have both single-phase lighting and three-phase motor loads. The bank wiring is similar to that of
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