B. WYE – 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 of transformer bank, two bushing conventional transformers of equal kVA rating are to be used. Primary Wiring: With a WYE connected high- voltage side, the H1 terminal of each transformer is typically connected to a different phase of primary. The H2 terminals are connected and allowed to form a “floating neutral”. NOTE: Do not connect the H2 terminals to ground . Grounding the floating neutral can create over-voltages during a fault event that can damage the transformers. Also note, the H2 bus is considered an energized conductor. 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
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