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I am trying to calculate the Full Load Amperage for this 150 kVA Transformer so that I can appropriately size the fuses for it.

The transformer is being supplied by two connections to a 3 phase system. One connection to line 1 & one connection to line 2 of the three phase system.

Will the transformer that these lines are feeding into also be considered a 3 phase transformer? Or will it be considered a 1 phase transformer?

The supply is 3 phase 480 VAC and the intention is to have 45 VAC coming out the secondary of the transformer.

I understand that calculating the FLA of a 3 phase transformer vs a 1 phase transformer is slightly different. For 3 phase it would be 150 kVA / 480 VAC * 1.73 and for 1 phase it would be 150 kVA / 480 VAC.

Just trying to figure out which calculation to use.

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  • \$\begingroup\$ 1,2,3 are different voltage "taps" of the same winding, even though they are not drawn. If your 480V happens to be more like 495V, the "1" tap might work better, and vice-versa for "3." 110kVA is a pretty big and heavy beast. \$\endgroup\$
    – rdtsc
    Aug 17, 2023 at 18:01
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    \$\begingroup\$ Please note, KVA = kelvinvoltampere, kVA = kilovoltampere. \$\endgroup\$
    – winny
    Aug 17, 2023 at 18:08

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Will the transformer that these lines are feeding into also be considered a 3 Phase Transformer? Or will it be considered a 1 Phase Transformer?

It's a single phase transformer with primary connected to a line voltage of 480 volts 60 Hz.

Just trying to figure out which calculation to use.

Single phase. But, add a bit more current for the transformer efficiency (maybe 99%)

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    \$\begingroup\$ Thanks. This is what I thought. \$\endgroup\$ Aug 17, 2023 at 18:09

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