inrush current is refers to maximum, instantaneous input
current drawn by electrical device when first turned on.
When a transformer is first energized a transient current much
larger than the rated transformer current can flow for several
cycles.this ts caused because the transformer will always have some
residual flux and when transformer is energized the incoming flux
will add to the already existing flux which will cause the
transformer to move in to saturation.
Due to this the starting current is double the rated
value. this us not a fault, our protecting system is
designed such a way that it can with stand with this inrush
current without any tripping.
while transformer is charges theres capacitive effect between turns of winding of x'-mer and it act as a capacitive load when switched on which in turns huge inrush current when switched on.