Phase current is the current in one of the 3 phases. Line current depends on the way line voltage is supplied from the utility that is either delta or star. That makes the difference.
There is a 30 degree phase shift from primary to secondary in a Delta-Wye (or Wye-Delta) wound transformer, due to the way the windings on common legs of the core are connected. Draw the phasor diagrams and you will see (or do a Google search!).
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3 Phase System
Re: 3 phase system
