the initial value of flux is zero when the transformer is energized. The, the flux reaches a peak value in half a cycle. Since power transformers operate near the knee of the saturation curve, a flux demand drives the transformer core deep into saturation, causing it to draw a very large magnetizing current with a peaky non-sinusoidal waveform. The magnetizing current is, therefore, very high, of the order of 8 to 30 times the full-load current. This current is known as inrush current.