C. DELTA – DELTA: 3-Wire, 3-Phase Service
A B C
H1 H2
H1 H2
H1 H2
X1
X3
X1
X3
X1
X3
Tank GND
Tank GND
Tank GND
X2
X2
X2
a b c
FOR A CORNER GROUNDED SERVICE, GROUND ONE OF THE PHASES. LEAVE FLOATING IF UNGROUNDED SERVICE IS REQUIRED.
For this type 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 is a straight delta and is utilized for electric services that are strictly Three-phase with no single-phase requirements. Typical services are 240V or 480V straight delta used for industrial loads, pumping stations, and other motor loads. For a delta connected secondary, the X2 terminals are connected to the X1 terminals on the adjacent transformers to form a “circle.”
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