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If one transformer of a three-transformer bank with a Delta secondary goes bad, the bank can be temporarily re-wired to an open bank. This can be useful in emergency situations.
Open Delta – Open Delta Banks
Open Delta – open Delta banks are used when the single-phase load is predominate over the three-phase load. Open banks are approximately 57.7% as e cient as closed banks.
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Chalk Talk: Open Delta- Open Delta lcvid.com/odod
Open banks are approximately 57.7% as e cient as closed banks.
n p h h
“Lighter” transformer
n - h h - h & h - p voltage voltage
120 240 240 480
H1
H2 H1 H2
Nameplate Rating 120/240 240/480
n - p voltage 208 416
h- h& h- p
x3x2x1 x3x2 x1
The voltage output is the same as with a Delta secondary utilizing three transformers.
ThREE-PhASE CONNECTIONS | CHaPTer sIX
n- p
voltage voltage voltage
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n- h
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norTHWesT LIneman CoLLeGe 67
