The magnetization current im is a current proportional (in the unsaturated region) to the voltage applied to the core and lagging the applied voltage by 90 degree, so it can be modeled by a reactance XM connected across the primary voltage source. The core- loss current i H is a
current proportional to the voltage applied to the core that is in phase with the applied voltage, so it can be modeled by a resistance Re connected across the primary voltage source. Why these components are installed in parallel to the applied voltage source, instead of series?

 

The magnetizing current appears to be drawn by the primary. Putting a load in series with the primary voltage would reduce the total current rather increase it.

Note that magnetizing current rarely is very sinusoidal (because of nonlinear B/H curve) and symmetric (because of hysteresis) in real-life AC power transformers.